Lanthanide metal-organic frameworks for catalytic oxidation of olefins

NJC

View Article Online

View Journal | View Issue

PAPER

Lanthanide metal–organic frameworks

for catalytic oxidation of olefins†

Cite this: New J. Chem., 2021,

45, 2090

Y. B. N. Tran^aband Phuong T. K. Nguyen

*

ab

Two isostructural lanthanide metal–organic frameworks (Ln-MOF-589, Ln = La³⁺, Ce³⁺), constructed

from tetratopic linker, benzoimidephenanthroline tetracarboxylic acid (H₄BIPA-TC), have been

a

solvothermally synthesized and characterized. These Ln-MOF-589 materials consist of Lewis acid

[Ln₂(-COO)₆(-COOH)₂(H₂O)₆] units and a naphthalene diimide core, which exhibited promising catalytic

activity for the oxidation of olefins. Among them, Ce-MOF-589 exhibited outstanding performance with

high conversions of styrene and cyclohexene (94 and 90%, respectively), and good selectivities towards

styrene oxide and 2-cyclohexen-1-one (85, and 95%, respectively). Notably, the catalytic activity of

Ce-MOF-589 outperformed that of homogeneous and heterogeneous catalysts, and representative

MOFs. Also, Ce-MOF-589 can be recycled for at least up to six cycles with no significant loss of

catalytic performance.

Received 21st November 2020,

Accepted 6th January 2021

DOI: 10.1039/d0nj05685e

rsc.li/njc

Metal–organic frameworks (MOFs) have emerged as a

potential heterogeneous catalyst.^5–9MOFs are one of the most

Introduction

Catalytic oxidation of alkenes/olefins to fine chemicals repre- widely studied crystalline materials constructed by combining

sents a significant process in organic synthesis and industrial inorganic metal clusters and organic linkers via strong bonds.¹⁰

production. The selective oxidation of olefins into epoxides has The variable functionalities, considerable thermal and

attracted tremendous attention since the epoxide products chemical stability, and well-ordered distribution of multiple

have a wide range of applications, including precursors for active sites inside MOFs’ pores make them suitable candidates

pharmaceutical synthesis and industrial intermediates for for heterogeneous catalysis for a variety of organic transforma-

making valuable products such as epoxy resins, paints, and tion reactions.^11–16In particular, MOFs containing lanthanide

surfactants.¹Allylic C–H oxidation of alkenes to the corres- (Ln) components and heteroatom-based functionalities have

ponding a,b-unsaturated enones or 1,4-enediones is particularly been demonstrated to be potential heterogeneous catalysts in

important in the synthesis of natural products and synthetic drug the oxidation of olefins.^5,9,17–21In particular, MOFs containing

precursors.²Numerous studies have been devoted to the develop- lanthanide (Ln) components and heteroatom-based function-

ment of homogeneous and heterogeneous catalysts for the oxida- alities have been demonstrated to be potential heterogeneous

tion of olefins.³However, it remains a challenge to achieve high catalysts in the oxidation of olefins. In this respect, the Ce-UiO-

selectivity in oxidation reactions.^1–3While many soluble metal 66-(CH₃)₂MOF was employed as the catalyst in the oxidation of

complexes have been demonstrated to be active in oxidation styrene with the use of the TBHP oxidant, showing high

reactions, several limitations remain, e.g., corrosion, deposition conversion (91%) and low selectivities of benzaldehyde (40%) and

on reactor walls, and difficulty in recovery and separation of the styrene oxide (33%).²²Another Cu-based MOF, [Cu₂(bipy)₂(btec)]_N,

catalyst from the reaction media. These disadvantages can be containing a bipyridine linker, was found to be a promising

overcome when using insoluble support-based catalysts embedded catalyst in the oxidation of olefins. The Cu-MOF showed an

with homogeneous active species and heterogeneous catalysts.⁴

average conversion of styrene (61%) and low selectivity of styrene

oxide (32%), while only 34% conversion of cyclohexene and 72%

selectivity of 2-cyclohexen-1-one formation were achieved.²³

Lanthanide-based MOFs (Ln-MOFs) constructed from

lanthanide ions are emerging as attractive Lewis acid catalysts

in various organic transformations.^24,25Some Ln-based metals

such as La and Ce, which are abundant and inexpensive rare earth

elements, have been widely studied in many applications.^26–28

Ln ions have high oxidation states, which could induce the

thermal robustness property of Ln-based frameworks. The large

^aFuture Materials & Devices Laboratory, Institute of Fundamental and Applied

Sciences, Duy Tan University, Ho Chi Minh City 700000, Vietnam.

E-mail: nguyentkieuphuong1@duytan.edu.vn

^bFaculty of Natural Sciences, Duy Tan University, Da Nang, 550000, Vietnam.

E-mail: nguyentkieuphuong1@duytan.edu.vn

† Electronic supplementary information (ESI) available: Experimental details,

MOF preparation, PXRD, IR, TGA, NMR, SEM, N₂, CO₂sorption, and catalytic

study. See DOI: 10.1039/d0nj05685e

2090 | New J. Chem., 2021, 45, 2090--2102

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

View Article Online

Paper

NJC

and variable coordination numbers of Ln ions prompt the (0.7 mol% of MOF catalyst, 75 1C, 10 h, solvent-free, and an N₂

formation of a high density of coordinated solvents binding environment). Among them, Ce-MOF-589 showed exceptional

to Ln sites, which, when removed, can produce unsaturated conversion of styrene and cyclohexene (94 and 90%, respectively)

metal sites serving as Lewis acid sites.²⁹However, the variable and high selectivities in the formation of styrene oxide (85%) and

coordination of Ln-based metals assists in the construction of 2-cyclohexen-1-one (95%). Furthermore, Ce-MOF-589 was shown

interpenetrating frameworks that have limited pore sizes and to be a robust catalyst and exhibited a heterogeneous nature with

low surface areas. Otherwise, the variety of Ln sources could no significant loss of catalytic performance over five consecutive

provide different strengths of Lewis acidity, resulting in diverse cycles.

catalytic activities for acid-catalyzed reactions. Furthermore,

Ln-MOFs containing Brønsted acid sites such as uncoordinated

carboxylic groups (from organic linkers) and hydroxyl moieties

(from water molecules coordinating to metal clusters) have

been demonstrated to enhance the conversion and selectivity

Experimental section

Materials and analytical techniques

of various catalytic transformations.³⁰Compared with the well- Full synthetic and characterization details are provided in the

established studies on homogeneous lanthanide-based compounds ESI† (Section S1). The H₄BIPA-TC linker was synthesized

and transition metal-based MOF catalysts, less has been according to a literature procedure.³⁰All chemicals for MOF

reported on the development of heterogeneous Ln-MOFs for synthesis and the catalytic reactions were purchased and used

the catalytic oxidation of olefins.^{21–23,31–33}

without purification. For comparison studies, commercial

Recently, some MOFs with embedded N-hydroxy- MOFs [HKUST-1 (Basolite C300), MOF-177 (Basolite Z377),

phthalimide (NHPI) revealed high selectivity in many oxidation ZIF-8 (Basolite Z1200), and Al-MIL-53 (Basolite A100)] were

transformations. In that context, NHPI species act as an purchased and re-activated to obtain guest-free materials prior

organocatalyst, which together with a transition metal can act to conducting any experiment. Ce-MOF-76 was prepared

as the initiator of radical chain oxidation.^34,35We previously according to a reported procedure (ESI,† Section S1).

reported the synthesis of a series of Ln-MOFs (MOF-589 to -592)

Elemental microanalyses (EA) were performed using a LECO

constructed from a benzoimidephenanthroline tetracarboxylic CHNS-932 analyzer. Fourier transform infrared (FT-IR) spectra

acid (H₄BIPA-TC) linker and Ln³⁺ions (Ln = Ce, Nd, Tb, Eu) were obtained on a Bruker Vertex 70 with samples being well-

and their wide applications in gas separation and catalytic dispersed in KBr pellets and the output signals are depicted as

transformations.^30,36Notably, the naphthalene diimide core vs, very strong; s, strong; m, medium; sh, shoulder; w, weak; vw,

of the H₄BIPA-TC linker has high electron aﬃnity, good charge very weak; or br, broad. Thermal gravimetric analysis (TGA)

carrier mobility, and excellent thermal and oxidative stability, curves were measured on a TA Q500 thermal analysis system

making it a promising candidate for the catalytic oxidation with the sample held in a platinum pan under a continuous flow

process.³⁷

of air. Low-pressure N₂and CO₂adsorption isotherms were

Herein, we further employ the H₄BIPA-TC linker for synthe- collected on a Micromeritics 3Flex with the use of He to estimate

sizing two isostructural Ln-based frameworks, called Ln-MOF-589 the dead space. A liquid N₂bath was used for measurements at

(Ln = La, Ce) (Fig. 1),³⁶and examine their catalytic properties in 77 K, and a circulating bath of ethylene glycol/water (1/1, v/v) was

the oxidation of olefins using anhydrous TBHP as an oxidant. The applied for measurements at 273, 283, and 298 K. Inductively

two Ln-MOF-589 materials showed eﬃcient catalytic performance coupled plasma mass spectroscopy (ICP-MS) data were collected

in the oxidation of styrene and cyclohexene under mild conditions on an Agilent ICP-MS 7700x instrument.

Fig. 1 Crystal structure of Ln-MOF-589. Linking of BIPA-TC^4ꢀand [Ln₂(-COO)₆(-COOH)₂(H₂O)₆] resulting in Ln-MOF-589. Color code: Ln, blue

polyhedra; C, black; N, light blue; O, red. All H atoms of the benzene units are omitted for clarity. Redrawn from CCDC deposition 1843313.

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

New J. Chem., 2021, 45, 2090--2102 | 2091

View Article Online

NJC

Paper

To identify the products of the catalytic reaction, gas (KBr, 4000–400 cm^ꢀ1): 3425 (s, br), 1714 (s), 1678 (s), 1618 (s), 1578

chromatography (GC) analysis was performed on an Agilent (s), 1552 (s), 1447 (s), 1388 (s), 1350 (s), 1255 (s), 1199 (w), 1120 (w),

GC system 19091s-433 equipped with a mass selective detector 985 (vw), 952 (vw), 912 (vw), 883 (vw), 779 (w), 767 (w), 745 (w),

(Agilent 5973N) (GC-MS) using a capillary HP-5MS 5% phenyl 721 (vw), 677 (w), 652 (vw), 609 (vw).

methyl silox column (30 m ꢁ 250 mm ꢁ 0.25 mm). The conver-

Catalytic studies

sion, selectivity, and yield of the catalytic reactions were deter-

mined by GC analysis using an Agilent GC system 123-0132

equipped with a flame ionization detector (FID) and a capillary

DB-1 ms column (30 m ꢁ 320 mm ꢁ 0.25 mm) with the use of

chlorobenzene as an internal standard.

For the catalytic oxidation, the reaction was performed in a

25 mL two-necked Schlenk-flask which is connected to a con-

denser. The flask was then placed in a temperature-controlled

oil bath and the reaction was carried out under a nitrogen

atmosphere. In a typical reaction, the flask was charged with

the catalyst (0.7 mol%, calculated based on metal sites), styrene

or cyclohexene (5 mmol), and anhydrous tert-butyl hydroper-

oxide (TBHP in decane, 10 mmol). The reaction mixture was

evacuated thoroughly to remove gas impurities and purged

three times with N₂. The reaction mixture was stirred at 75 1C

for 10 h. The progress of the reaction was monitored by

analyzing regularly taken aliquots with GC. After completion

of the reaction, the MOF catalyst was isolated by centrifugation,

and an aliquot of the reaction was analyzed by GC-FID using

chlorobenzene as the internal standard. For the recycling

experiment, the recovered catalyst was rinsed with ethanol

(3 ꢁ 3 mL) before heating at 60 1C under a vacuum for 24 h

and then reused for the next cycles. To emphasize the reprodu-

cibility of the catalytic results, all catalytic reactions were

conducted three times, and the results were obtained with

standard deviations.

X-ray photoelectron spectroscopy (XPS) measurements were

performed at Sungkyunkwan University (South Korea), using a

Thermo Scientific K-Alpha X-ray photoelectron spectrometer

with a non-monochromatic Al-Ka (hn = 1486.6 eV) source. The

binding energy data were calibrated with reference to the C 1s

signal at 284.8 eV and O 1s signal at 531.0 eV. All the spectra

were obtained with a pass energy of 25 eV, step increment of

0.1 eV, and total scans of 20. The experimental data were curve

fitted with a Gaussian–Lorentzian model using Shirley back-

ground subtraction implemented in the Origin 9.0 program.

The spin–orbit splitting and doublet intensities were fixed

during the curve fitting.

X-ray diﬀraction analysis

Powder XRD (PXRD) patterns were measured using a Bruker D8

Advance diﬀractometer with Ni-filtered Cu Ka (l = 1.54178 Å)

radiation operated at 40 kV and 40 mA (1600 W). The system

was outfitted with an anti-scattering shield to avoid incident

diﬀuse radiation hitting the detector. MOF samples were

mounted on zero background holders and then well-flattened

using a spatula. PXRD patterns were recorded with a 2y range

from 3 to 501, a step size of 0.021, and a fixed count time of

1 s per step.

Results and discussion

Synthesis and structural characterization

The organic H₄BIPA-TC linker was synthesized by a one-step

condensation reaction of 1,4,5,8-naphthalenetetracarboxlic

dianhydride and 5-aminoisophthalic acid. The preparation of

Synthesis of Ln-MOF-589

Ce-MOF-589. Ce-MOF-589 was prepared according to a La-MOF-589 was accomplished in direct analogy with Ce-MOF-

published procedure.³⁶EA of activated sample: calcd for 589,^30,36in which two yellow-block Ln-MOF-589 (Ln = La, Ce)

CeC₃₀H₁₃N₂O₁₃= [Ce(HBIPA-TC)]ꢂH₂O: C, 48.70; H, 1.75; N, crystals were obtained by solvothermal reactions between

3.74. Found: C, 48.51; H, 1.89; N, 3.68. FT-IR (KBr, 4000– H₄BIPA-TC and hydrated Ln(NO₃)₃(Ln = La, Ce) in a solvent

400 cm^ꢀ1): 3425 (s, br), 1714 (s), 1678 (s), 1618 (s), 1578 (s), mixture of water, DMA, and CH₃COOH. The resulting micro-

1552 (s), 1447 (s), 1388 (s), 1350 (s), 1255 (s), 1199 (w), 1120 (w), crystalline Ln-MOF-589 (Ln = La, Ce) materials were achieved in

985 (vw), 952 (vw), 912 (vw), 883 (vw), 779 (w), 767 (w), 745 (w), high yield (460%) and exhibited a homogeneous morphology

721 (vw), 677 (w), 652 (vw), 609 (vw).

when examined using optical microscope images (Fig. S1 and

La-MOF-589. La(NO₃)₃ꢂxH₂O (0.044 g, 0.01 mmol) and S2, ESI†). The synthesis of the bulk La-MOF was confirmed by

H₄BIPA-TC (0.060 g, 0.01 mmol) were inserted in a glass 8 mL PXRD analysis, whereas the pattern of the as-synthesized

vial containing a mixture of H₂O (2 mL), DMA (1 mL), and La-MOF sample was in good agreement with that of Ce-MOF-589

CH₃COOH (400 mL). The vial was accordingly sealed and heated (Fig. 2), suggesting that the La-MOF is reticular with the

to 120 1C for 15 h in an isothermal oven, yielding yellow block Ce-MOF-589 structure. Although the length of the La-MOF

crystals of La-MOF-589. The as-synthesized La-MOF-589 was crystal was suﬃcient, its thickness and width were not satis-

washed with DMF (3 ꢁ 10 mL) once a day for 3 days and factory for single-crystal X-ray diﬀraction study. Therefore, the

accordingly exchanged in anhydrous EtOH (3 ꢁ 10 mL) once a crystal structure of the La-MOF was instead determined by

day for 3 days. The solid was then dried at ambient temperature full profile matching Pawley refinement of powder X-ray

under a vacuum for 18 h, followed by heating at 60 1C for an diﬀraction (PXRD) data. In this respect, the crystal model of

additional 24 h to yield an activated sample. EA of activated the La-MOF-589 structure was prebuilt by replacing the Ce³⁺ion of

sample: calcd for LaC₃₀H₁₃N₂O₁₃= [La(HBIPA-TC)]ꢂH₂O: C, Ce-MOF-589 (CCDC number 1843313) with a La³⁺ion, and the

48.15; H, 1.75; N, 3.74. Found: C, 48.26; H, 1.66; N, 3.56. FT-IR Pawley refinement was accordingly performed (ESI,† Section S2).

2092 | New J. Chem., 2021, 45, 2090--2102

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

View Article Online

Paper

NJC

Fig. 2 Powder X-ray diﬀraction patterns of experimental La-MOF-589

(blue) and Ce-MOF-589 (red).

Fig. 3 FT-IR spectra of the H₄BIPA-TC linker (black), La-MOF-589 (red),

and Ce-MOF-589 (blue).

As depicted in Fig. S3 (ESI†), there was a good match between

the initial and the refined unit cell parameters of La-MOF-589.

According to the structural refinement, La-MOF-589 crystallizes in

%

the triclinic P1 space group with unit cell parameters of a = 8.2030

Å, b = 11.0561 Å, and c = 17.4692 Å. Similar to Ce-MOF-589, the additional sharp peaks at 1552 and 1618 cm^ꢀ1for La-MOF-589,

structure of La-MOF-589 is built up from dinuclear [La₂(-COO)₆- and 1553 and 1619 cm^ꢀ1for Ce-MOF-589, assigned as asymmetric

(-COOH)₂(H₂O)₆] units, which are interconnected by BIPA-TC vibrations of the carboxylate group, suggested the emergence of

ligands to form a parallelogram channel and window size of metal–carboxylate coordination.

5.5 ꢁ 10.4 Å²(Fig. 1A). In the two isostructural Ln-MOF-589

Thermogravimetric analyses of the Ln-MOF-589 frameworks

materials, the distance between two neighboring BIPA-TC units were performed on activated MOF samples under an air-flow

is approximately 3.0 Å, which could aﬀord p–p interactions and environment and a heating rate of 5 1C per minute (Fig. S8,

improve the structural stability of the Ln-based frameworks ESI†). As shown in Fig. S8 (ESI†), the TGA curves exhibited

(Fig. 1B).

insignificant weight loss in the temperature range from 25 to

To assess the successful synthesis of microcrystalline 150 1C, corresponding to the loss of guest water molecules. The

Ln-MOF-589, the PXRD analysis of the as-synthesized and major weight loss observed at 400 and 350 1C for La-MOF-589

activated Ln-MOF-589 samples was compared to that of the calcu- and Ce-MOF-589, respectively, was attributed to framework

lated patterns from the crystal structures. The as-synthesized destruction (Fig. S8, ESI†). Analyses of the weight percent of

Ln-MOF-589 materials were solvent-exchanged with dry EtOH, residual metal oxide for La-MOF-589 (21.54%) and Ce-MOF-589

followed by vacuum activation at elevated temperatures to gen- (22.05%) exhibited good agreement with the calculated values

erate activated Ln-MOF-589 materials. As such, the PXRD patterns derived from EA (21.77 and 21.88%, respectively).

of the activated Ln-MOF-589 samples presented good agreement

The permanent porosity of the activated Ln-MOF-589 frame-

with those of the as-synthesized ones and those calculated from works was evaluated by collecting N₂sorption isotherms

the crystal structures (Fig. S4 and S5, ESI†), indicating that the two at 77 K. As illustrated in Fig. 4A, the two Ln-MOF-589 materials

Ln-MOFs retained their frameworks upon the activation process. exhibited

Moreover, the FT-IR spectra of the Ln-MOFs showed identical Ln-MOF-589 possesses

a

type-I sorption profile, demonstrating that

feature of micropore structure.

a

characteristic peaks, suggesting the isostructural nature of the two Furthermore, the isotherms of the two Ln-MOF-589 frameworks

Ln frameworks (Fig. 3). As shown in Fig. S7 (ESI†), FT-IR analysis revealed moderate hysteresis at the high-pressure region

of the dried Ln-MOF-589 showed sharp peaks at 1714 and (P/P₀4 0.45), indicating framework flexibility or guest molecule

1678 cm^ꢀ1according to the amide carbonyl stretching vibrations. rearrangement. The Brunauer–Emmett–Teller (BET)/Langmuir

The two Ln-MOFs presented absorption bands at B1578 and surface areas for La-MOF-589 and Ce-MOF-589 were

1447–1388 cm^ꢀ1corresponding to the antisymmetric and sym- estimated to be 12/13 and 16/25 m²

g

^ꢀ1, respectively. From

metric carbonyl COO^ꢀvibrations. This evidence indicated the the N₂isotherms, the pore size distributions of the two

presence of the carboxylate group in the Ln-MOF-589 structures. Ln-MOFs were calculated by fitting nonlocal density functional

Broad peaks at about 3436 cm^ꢀ1associated with the stretching theory models. As expected, the calculated values were in

modes of water molecules were also observed in the two frameworks. line with the pore aperture metrics derived from the crystal

In comparison to the free H₄BIPA-TC ligand, the generation of structures (Fig. 4A).

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

New J. Chem., 2021, 45, 2090--2102 | 2093

View Article Online

NJC

Paper

Fig. 4 (A) N₂sorption isotherms at 77 K, (inset) pore size distribution analyses based on the DFT method, and (B) CO₂sorption isotherms at 273 K for La-

MOF-589 (red) and Ce-MOF-589 (blue).

The CO₂sorption isotherms at 273 K for the two Ln-MOFs

The type of solvent has an eﬀect in the catalytic oxidation

had typical type I shapes with small degrees of adsorption/ of olefins. Highly polar alkylamine solvents (e.g., DMF and

desorption hysteresis (Fig. 4B). At 800 Torr, the total CO₂acetonitrile) exhibit high activity in the oxidation reaction.³⁹

uptake of La-MOF-589 (21.3 cm³g^ꢀ1) was higher than that of In our work, we initially examined the eﬀect of the solvent

Ce-MOF-589 (4.2 cm³^ꢀ1). Notably, the La-based framework (5 mL) on the catalytic oxidation of styrene catalyzed by

g

also exhibited a broader extension of hysteresis than the Ce- Ce-MOF-589 by employing non-polar (i.e., toluene) and polar

based framework, suggesting diﬀerent interactions between (i.e., ethanol and acetonitrile) solvents in the model reaction.

each Ln-MOF-589 framework and CO₂. When raising the activa- Among the examined solvents, ethanol showed the lowest

tion temperature for La-MOF-589 and Ce-MOF-589 to 90 1C, the conversion of styrene (20%) and the highest selectivity in

total CO₂uptake for the two Ln-MOF-589 compounds was lower styrene oxide formation (73%) (Fig. 5). In contrast, acetonitrile

than that of the frameworks activated at 60 1C (Fig. S9 and S10, displayed the highest conversion (64%) and the lowest selectivity

ESI†). It can be explained by the fact that water molecules that in styrene oxide production (63%). The non-polar toluene solvent

coordinate to open-Ln sites and are retained inside the MOF’s exhibited a lower yield of styrene oxide (34%) than the polar

pores could aﬀord weak coordination to CO₂induced by the acetonitrile solvent (41%). Notably, the solvent-free condition

quadrupole moment of CO₂and the electric field created by

water molecules, thus increasing the total CO₂uptake.³⁸

A

broad hysteresis loop of La-MOF-589 was also noted, which

indicated that the adsorbed CO₂was trapped within the frame-

work and not desorbed immediately upon reducing the external

pressure. It is worth noting that the La and Ce-based frame-

works have a similar surface area and the same structure but

showed diﬀerent CO₂sorption behaviours. This result was

attributed to the diﬀerent Ln-based metals, which aﬀorded

diﬀerent interactions with CO₂.

Catalytic studies

In the Ln-MOF-589 (Ln = La, Ce) structures, the Ln clusters have

large coordination with water molecules, which can aﬀord

accessible Lewis and Brønsted acid sites. By taking advantage

of the high density of catalytic acid sites and the intrinsic

nature of the electron-rich naphthalene diimide core, the

Ln-MOF-589 materials were eﬃcient platforms for the catalytic

oxidation reaction. To achieve the optimized reaction conditions,

we first used the Ce-MOF-589 framework as a model platform

to investigate the impacts of solvent type, temperature, catalyst

amount, oxidant type, and oxidant ratios.

Fig. 5 Catalytic performances in styrene oxidation catalyzed by

Ce-MOF-589 in diﬀerent solvents. Error bars indicate the range of data

based on three repeat experiments.

2094 | New J. Chem., 2021, 45, 2090--2102

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

View Article Online

Paper

NJC

revealed the best catalytic performance with a conversion of 94%

and a yield of styrene oxide of 80% for 10 h.

The eﬀect of temperature on the oxidation of styrene was

accordingly examined in the range of 25–85 1C (Fig. 6). Notably,

the reaction performed at room temperature showed neither

conversion of styrene nor styrene oxide formation after 10 h.

At 65 1C, the oxidation exhibited a moderate performance with

72% conversion of styrene and a 52% yield of styrene oxide.

When the reaction temperature increased from 65 to 75 1C, the

conversion of styrene increased correspondingly (from 72 to

94%), resulting in a high yield of styrene oxide (80%) at 75 1C.

Further increasing the temperature to 85 1C, no considerable

variation in the conversion of styrene (95%) was observed, but

the selectivity and yield of styrene epoxide slightly dropped to

66 and 70%, respectively. We proposed that the decrease of the

styrene oxide selectivity was associated with the increase of the

temperature, suggesting that the vinyl C–H bonds of styrene

molecules are very active and readily oxidized to other products

at high temperature.⁴⁰Therefore, 75 1C was chosen as the

control temperature for further studies.

Fig. 7 Catalytic performances in styrene oxidation catalyzed by

Ce-MOF-589 at diﬀerent amounts of MOF catalyst. Error bars indicate

the range of data based on three repeat experiments.

Subsequently, the eﬀect of the catalyst amount on the

oxidation reaction was investigated by carrying out the reaction

with 0, 0.3, 0.5, 0.7, and 0.9 mol% (calculated based on metal

sites) of the Ce-MOF-589 catalyst (Fig. 7). We noted that the

blank reaction without the MOF catalyst presented the lowest of active sites, resulting in enhancing the styrene oxidation

performance with a 28% conversion of styrene and an 18% rate. In contrast, overuse of MOF catalysts could block the

yield of styrene oxide. When the catalyst amount increased active sites and reduce the solid–liquid interactions between

from 0.3 to 0.7 mol%, the conversion of styrene and selectivity catalysts and reactants, yielding lower catalytic activity. Thus, a

of styrene oxide dramatically increased with rises of 44 and catalyst loading of 0.7 mol% was the optimized value for

39%, respectively. However, a further increase of the MOF obtaining the highest catalytic performance.

amount to 0.9 mol% was ineﬀective and instead resulted in

The oxidant type also exhibited an influence on the oxida-

lower selectivity (80%) and yield (76%) of styrene oxide. This tion of styrene catalyzed by Ce-MOF-589. Diﬀerent oxidants

result indicated that the assessment of suﬃcient catalyst such as H₂O₂, NaIO₄, and aqueous TBHP (70% in water) were

aﬀords a more accessible surface area with a high distribution employed in the catalytic oxidation of styrene. As depicted in

Fig. 8, the media using H₂O₂and NaIO₄exhibited the lowest

activities among the oxidants examined with styrene oxide

yields of 1% and 2%, respectively. Otherwise, aqueous TBHP

showed moderate catalytic performance with a styrene conver-

sion of 70% and styrene oxide yield of 45%. Notably, the

oxidation promoted by anhydrous TBHP (TBHP in decane)

exhibited the highest eﬃciency with a conversion of 94% and

a yield of styrene oxide of 80%.

The eﬀect of the styrene/TBHP molar ratio on the generation

of styrene oxide was consequently studied by conducting the

reaction at diﬀerent molar ratios of 1 : 1, 1 : 2, and 1 : 3. Moderate

catalytic performance with a conversion of 60% and selectivity of

53% was observed at a molar ratio of 1 : 1, associated with lower

availability of active oxidant to interact with the substrate. When

the molar ratio increased to 1 : 2, the conversion of styrene and the

selectivity of styrene oxide formation increased to 94 and 85%,

respectively (Fig. 9). It was attributed to the higher amount of

TBHP adsorbed on the active sites, thereby leading to more

interaction with styrene molecules. When the styrene/TBHP molar

ratio reached 1 : 3, the conversion of styrene slightly increased,

Fig. 6 Catalytic performances in styrene oxidation catalyzed by

but the selectivity and yield of styrene oxide gradually decreased.

We noted that an excess amount of TBHP could improve the

Ce-MOF-589 at diﬀerent temperatures. Error bars indicate the range of

data based on three repeat experiments.

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

New J. Chem., 2021, 45, 2090--2102 | 2095

View Article Online

NJC

Paper

Fig. 8 Catalytic performances in styrene oxidation catalyzed by Ce-MOF-

589 in diﬀerent oxidants. Error bars indicate the range of data based on

three repeat experiments.

Fig. 10 Oxidation product distribution at diﬀerent reaction times. Error

bars indicate the range of data based on three repeat experiments.

styrene oxide increased rapidly (a rise of 32%) with the presence

of trace amounts of benzaldehyde and phenylacetaldehyde

by-products. Low selectivity and yield of these by-products were

observed within 8 h and they slightly increased at prolonged

reaction time. Interestingly, high selectivities (85–90%) in

styrene oxide formation were noted during the oxidation of

styrene catalyzed by Ce-MOF-589.

With the optimized conditions, the catalytic activity in the

epoxidation of styrene for La-MOF-589 was accordingly exam-

ined (Table 1). As such, La-MOF-589 exhibited lower catalytic

performance (a conversion of 60%, selectivity of 78%, and yield

of 47%) compared to Ce-MOF-589 (a conversion of 94%,

selectivity of 85%, and yield of 80%). Benzaldehyde and

phenylacetaldehyde were also found to be by-products and

occurred in trace amounts during the oxidation reaction cata-

lyzed by La-MOF-589. We noticed that the two Ln-MOF-589

materials are isostructural and have similar aperture sizes,

but the Ce-based framework exhibited higher activity than the

Fig. 9 Catalytic performances in styrene oxidation catalyzed by Ce-MOF-

589 for diﬀerent molar ratios of styrene and TBHP. Error bars indicate the

range of data based on three repeat experiments.

Table 1 Catalytic styrene oxidation catalyzed by Ln-MOF-589^a

conversion of styrene and also facilitate the oxidation of styrene

oxide to benzaldehyde and phenylacetaldehyde. From this view-

point, a styrene/TBHP ratio of 1 : 2 exhibited the best activity

among the examined conditions.

To gain insight into the oxidation reaction, the product

distribution at diﬀerent reaction times was investigated

(Fig. 10). Under an N₂environment, the conversion of styrene

reached 36% after 2 h and obtained a maximized value of 94%

for 10 h. Because of no significant increase in the conversion of

styrene and a slight decrease in the yield of styrene oxide,

further increasing the reaction time after 10 h was found to be

Selectivity^b/%

Catalyst

Conversion^b/%

1

2

3

Yield^b/%

La-MOF-589

Ce-MOF-589

No catalyst

60

94

28

78

85

64

41

12

26

12

3

10

47

80

18

a

Reaction conditions: styrene (5 mmol), catalyst (0.7 mol%, based on

b

metal sites), TBHP (10 mmol), 75 1C, 10 h. The conversion, selectivity,

and yield of the main product (styrene oxide) were determined by

GC-FID analysis using chlorobenzene as the internal standard.

ineﬀective. At the early stage of the reaction, the formation of 1 = styrene oxide, 2 = benzaldehyde, and 3 = phenylacetaldehyde.

2096 | New J. Chem., 2021, 45, 2090--2102

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

View Article Online

Paper

NJC

La-based structure. It could be explained by the easy formation high surface area and high total CO₂uptake at room temperature

of the stable (+IV) oxidation state of the Ce ion according to its are not the most decisive factors for catalytic epoxidation. This

vacant f-shell.

evidence supports the exceptional performance of Ce-MOF-589

The catalytic activities of the Ln-MOF-589 frameworks for and the synergic eﬀect of Lewis acid [Ce₂(-COO)₆(-COOH)₂(H₂O)₆]

the epoxidation of styrene were comparable with those of some units and the naphthalene diimide-based linker within

of the homogenous and heterogeneous catalysts, and MOFs Ce-MOF-589 for the catalytic oxidation reaction.

reported before (Table 2). Accordingly, homogenous Ce salts

Encouraged by the above results, we further investigated the

Ce(NO₃)₃ꢂ6H₂O and [Ce(NO₃)₆](NH₄)₂showed high conversions oxidation of cyclohexene catalyzed by two Ln-based frameworks

of styrene (84 and 98%, respectively) but low selectivities of (Table 3). We noted that the blank reaction without any catalyst

styrene oxide (3%). Among homogenous Ln salts, La(NO₃)₃ꢂ gave a negligible conversion (30%) and a low yield of

6H₂O exhibited poor performance with moderate conversion 2-cyclohexen-1-one (17%). Under the optimum conditions,

(54%) and the lowest selectivity of epoxide (2%), compared to 2-cyclohexen-1-one and cyclohexene-3-(tert-butyl)peroxide were

that of La(CH₃COO)₃ꢂxH₂O (41% conversion and 81% selectivity). obtained as major products, and only a trace amount of cyclo-

Moreover, a catalytic reaction using the H₄BIPA-TC linker showed hexene epoxide and 2-cyclohexen-1-ol was detected. As shown

moderate performance with 25% conversion of styrene and only a in Table 3, Ce-MOF-589 exhibited outstanding performance

14% yield of styrene oxide. Furthermore, oxidation reactions with a high conversion of cyclohexene (90%) and a high yield

catalyzed by mixtures of La(NO₃)₃ꢂ6H₂O/H₄BIPA-TC and of 2-cyclohexen-1-one (85%). In contrast, La-MOF-589 showed a

Ce(NO₃)₃ꢂ6H₂O/H₄BIPA-TC resulted in moderate conversions moderate transformation of cyclohexene to 2-cyclohexen-1-one

of styrene (62 and 86%, respectively) and low selectivities of (a conversion of 54% and yield of 49%). Remarkably, the two

styrene oxide formation (38 and 43%, respectively). This evi- Ln-MOF-589 frameworks exhibited excellent catalytic selec-

dence supported the high catalytic activity of the Ce-MOF-589 tivities for 2-cyclohexen-1-one formation (90–95%). It is worth

framework constructed from Ce-based clusters and the noting that the cyclohexene oxidations catalyzed by the two

naphthalene diimide linker. Moreover, heterogeneous La₂O₃Ln-based structures were highly selective towards the 2-cyclo-

and CeO₄solids facilitated low eﬃciencies with styrene oxide hexen-1-one product in the model experiment because the

yields of 19 and 31%, respectively. Interestingly, Ce-MOF-589 allylic hydrogen is generally more reactive than the double

exhibited a higher activity than representative MOFs with larger bond of the cyclic fragment.

surface areas such as HKUST-1, ZIF-8, MIL-53, MOF-177, and

A leaching experiment was performed to verify the hetero-

Ce-MOF-76. Among these comparative MOFs, MIL-53 revealed geneity of the reaction (Fig. 11). The Ce-MOF-589 catalyst was

the lowest catalytic activity, reaching only a 6% yield of styrene isolated at 4 h and the supernatant reaction was allowed to

oxide, while Ce-MOF-76 was the most active with a 46% yield proceed for an additional 6 h under similar conditions. As

achieved. By comparing these results, it is worth noting that shown in Fig. 11, no significant increase in styrene oxide

formation was observed. The result confirmed the heterogene-

ity of the catalytic oxidation reaction, and the contribution of

Table 2 Comparison of the catalytic performance of representative

homogeneous Ce³⁺leaching from the Ce-MOF-589 structure to

catalysts^a

the generation of styrene oxide was unimportant. Furthermore,

ICP-MS of the reaction filtrate demonstrated that a trace

amount of Ce³⁺ions was observed (o0.085 ppm), confirming

the structural stability of Ce-MOF-589 upon catalytic oxidation.

#

Type Catalyst

Con.^b/% Sel.^b/% Yie.^b/%

1

2

3

4

5

6

7

8

9

Hom. La(NO₃)₃ꢂ6H₂O

La(CH₃COO)₃ꢂxH₂O

Ce(NO₃)₃ꢂ6H₂O

54

41

84

98

25

2

81

3

1

33

2

Table 3 Catalytic cyclohexene oxidation catalyzed by Ln-MOF-589^a

[Ce(NO₃)₆](NH₄)₂

H₄BIPA-TC linker

3

56

38

43

48

60

78

85

54

48

8

14

24

37

19

31

47

80

47

43

6

La(NO₃)₃ꢂ6H₂O + H₄BIPA-TC 62

Ce(NO₃)₃ꢂ6H₂O + H₄BIPA-TC 86

Het.

La₂O₃

CeO₄

40

52

60

94

86

90

67

34

85

Selectivity^b/%

10 MOF La-MOF-589

Catalyst

Conversion^b/%

1

2

3+4

Yield^b/%

11

12

13

14

15

16

Ce-MOF-589

ZIF-8

HKUST-1

MIL-53

MOF-177

Ce-MOF-76

La-MOF-589

Ce-MOF-589

No catalyst

54

90

30

4

2

16

90

95

58

6

3

26

49

85

17

32

54

11

46

a

Reaction conditions: cyclohexene (5 mmol), catalyst (0.7 mol%, based

b

a

on metal sites), TBHP (10 mmol), 75 1C, 10 h. The conversion (Con.),

Reaction conditions: styrene (5 mmol), catalyst (0.7 mol%, based on

b

selectivity (Sel.), and yield of the main product (Yie.) were determined

by GC-FID analysis using chlorobenzene as the internal standard. 1 =

cyclohexene oxide, 2 = 2-cyclohexen-1-one, and 3+4 = cyclohexene-3-

(tert-butyl)peroxide + 2-cyclohexen-1-ol.

metal sites), TBHP (10 mmol), 75 1C, 10 h. Conversion (Con.),

selectivity (Sel.), and yield (Yie.) were determined by GC-FID analysis

using chlorobenzene as the internal standard. Hom. = homogeneous,

and Het. = heterogeneous.

This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021

New J. Chem., 2021, 45, 2090--2102 | 2097

View Article Online

NJC

Paper

no significant change in the peak intensity and position (ESI,†

Fig. S21 and S22), implying that the Ce-based framework

retained its structural integrity after several catalytic reactions.

As depicted in Fig. S23 (ESI†), the SEM image of Ce-MOF-589

after the 6th cycle also confirmed that Ce-MOF-589 maintained

its particle morphology over several catalytic reactions. We also

found that the yellow color of the large-scale Ce-MOF-589 solid

was unchanged after several catalytic reactions, as illustrated in

Fig. S24 (ESI†).

Reaction mechanism

Because of the narrow aperture size of Ce-MOF-589 (5.6 ꢁ

11.4 Å²), the activation of Ce³⁺by the TBHP (t-BuOOH) oxidant

generally occurred on the external surface of Ce-MOF-589.

Through the interaction with t-BuOOH, Ce(^III)-MOF-589 trans-

formed to Ce(^IV)-MOF-589 owing to the presence of a vacant

f-shell (the electron configuration of Ce³⁺is [Xe]4f¹5d⁰6s⁰).

Therefore, the catalytic activity of Ce-MOF-589 is higher com-

pared to La-MOF-589, due to the lack of a vacant f-shell (the

electron configuration of La³⁺is [Xe]5d⁰6s⁰).

To confirm the oxidation state of the Ce ion within Ce-MOF-

589, XPS was performed on the activated Ce-MOF-589 sample.

As depicted in Fig. 13, the Ce 3d core-level spectrum revealed

the presence of v and u multiplets assigned to spin–orbit split

3d_5/2and 3d_3/2core holes, respectively.^41–44Three peaks of

binding energies at 880.1, 884.1, and 903.3 eV corresponding

to v₀, v⁰, and u⁰, respectively, were ascribed to be characteristics

of Ce³⁺. Otherwise, three peaks attributed to Ce⁴⁺, whose

binding energies were at 883.5, 898.6, and 901.9 eV, labeled

as v, v⁰⁰, and u, respectively, were also observed. This result

suggested that the activated Ce-MOF-589 is possibly composed

of a mixed-valence state of Ce³⁺and Ce⁴⁺. From the integrated

peak area, the relative amount of Ce³⁺was accordingly estimated

to be 83%. This observation indicated that the Ce-MOF-589

framework contains mostly Ce³⁺. We supposed that the presence

of Ce⁴⁺in the activated Ce-MOF-589 sample could be attributed to

Fig. 11 Time dependent yield of styrene oxide in leaching, TEMPO, and

no-MOF experiments. Error bars indicate the range of data based on three

repeat experiments.

Subsequently, the reusability of the Ce-MOF-589 catalyst for

the oxidation of styrene was examined under the optimized

reaction conditions (Fig. 12). Remarkably, Ce-MOF-589 was

recovered and reused up to six times without any significant

decrease in catalytic activity, which was demonstrated by the

reasonable average values of conversion (92%), selectivity

(79%), and yield (73%) of styrene oxide. Furthermore, the PXRD

and FT-IR analyses of the reused Ce-MOF-589 catalyst showed

Fig. 12 Recycling study for Ce-MOF-589. Error bars indicate the range of

Fig. 13 XPS spectrum of the Ce 3d core level of the activated

data based on three repeat experiments.

Ce-MOF-589.

2098 | New J. Chem., 2021, 45, 2090--2102

View Article Online

Paper

NJC

the partial oxidization of Ce(III)-MOF to Ce(IV)-MOF under an air to form a Ce(^IV)-peroxy adduct. Then, the Ce(IV)-peroxy adduct

environment.

releases the t-BuOO^ꢃradical, and Ce(III)-MOF is regenerated. It is

According to previous literature, diﬀerent intermediates followed by a reaction between the t-BuOO^ꢃradical and olefin,

could be generated when the transition metal site interacts forming a benzylic t-butylperoxy radical. The benzylic t-butyl

with t-BuOOH.^23,45–47There are two major pathways involved: peroxy radical either (i) undergoes migration of oxygen, yielding

(i) the production of free radical intermediates such as t-BuOO^ꢃthe styrene oxide and t-BuOH (Scheme 1, route I); or (ii) reacts

and/or t-BuO^ꢃradicals; and (ii) the concerted addition of with t-BuOO^ꢃ, producing benzaldehyde via oxidative C–C bond

oxygen, yielding high valent metal-peroxo and/or metal-oxo cleavage (Scheme 1, route II).

species. To ascertain the nature of styrene oxidation catalyzed by

A ring-opening of styrene oxide with t-BuOOH followed by

Ce-MOF-589, a radical scavenger, 2,2,6,6-tetramethylpiperidine-1- C–C cleavage could occur, resulting in benzaldehyde. Moreover,

oxyl (TEMPO, 1 equiv. to the moles of TBHP used), was added into the benzylic t-butylperoxy radical can undergo the migration of

the medium at the beginning of the reaction. A trace amount of hydrogen to a benzylic carbon and simultaneous cleavage of O–O

styrene oxide (yield of 3%) was observed after 10 h (Fig. 11). When (Scheme 1, route III), resulting in phenylacetaldehyde and t-BuOH.

TEMPO was added into the medium after 2 h (36% conversion Otherwise, the Lewis-acid Ce(^III) sites can induce a ring-opening

obtained), the reaction stopped producing styrene oxide immedi- isomerization of styrene oxide, which involves hydride migration

ately (Fig. 11). Accordingly, a slight decrease in the yield of styrene and the regeneration of active Ce(^III) sites, affording phenyl-

oxide was observed after 8 h reaction time (Fig. 11). This result acetaldehyde.^50,51These proposed pathways confirmed the experi-

could be explained by the formation of phenylacetaldehyde and mental result indicating that the higher the amounts of t-BuOOH

benzaldehyde from the consequent reactions of styrene oxide with or Ce-MOF-589 catalyst compared to those of the optimized condi-

Ce sites and styrene oxide with TBHP, respectively. All of the tions used, the lower the selectivities and yields of styrene oxide

evidence suggested that the mechanism of the oxidation of styrene achieved. That is due to the consequent reactions between the

proceeded mainly via a radical process.^48,49

resulting styrene oxide and the excess t-BuOOH and/or Ce-MOF-589.

Accordingly, the mechanism of styrene oxidation was

As for the oxidation of cyclohexene, there was no signifi-

proposed (Scheme 1). First, Ce(^III)-MOF-589 reacts with t-BuOOH cant change in the conversion of cyclohexene and yield of

Scheme 1 Possible mechanism for the oxidation of styrene catalyzed by Ce-MOF-589.

New J. Chem., 2021, 45, 2090--2102 | 2099

View Article Online

NJC

Paper

and t-BuO^ꢃradical species are produced from the interaction

between TBHP and Ce(^III) centers.⁵⁴As illustrated in Scheme 2,

route-I revealed hydrogen transfer from a-C-H of cyclohexene to

t-BuO^ꢃand/or t-BuOO^ꢃradicals, resulting in cyclohexenyl radicals.

Subsequently, the cyclohexenyl radical combines with the

t-BuOO^ꢃradical to aﬀord the cyclohexene-3-(-(tert-butyl)-

peroxide) product.⁵⁵Also, the cyclohexenyl radical could react

with O₂, generated from the combination of two t-BuOO^ꢃ

radicals, to produce the cyclohexenyl peroxy radical. Accord-

ingly, the cyclohexenyl peroxy radical undergoes an elimina-

tion reaction to form 2-cyclohexen-1-one and 2-cyclohexen-1-ol.

Also, the t-BuOO^ꢃradical can combine with the CQC bond,

yielding the cyclohexyl 2-peroxide radical. The intermediate

accordingly undergoes ring-closing to produce cyclohexene oxide

(Scheme 2, route II).⁵⁶

Conclusions

Fig. 14 Time dependent yield of 2-cyclohexen-1-one in TEMPO and no-

MOF experiments. Error bars indicate the range of data based on three

repeat experiments.

In summary, two isostructural lanthanide-based MOFs, namely

Ln-MOF-589 (Ln = La, Ce), were synthesized and characterized.

In this series, Ce-MOF-589 exhibited the higher surface area but

lower total CO₂uptake (at 298 K and 800 Torr), compared to

those of Ln-MOF-589. As for the catalytic oxidation, Ce-MOF-589

exhibited the highest catalytic conversions of styrene (94%) and

cyclohexene (90%) by using anhydrous TBHP oxidant, and under

mild conditions (solvent-free, 75 1C, N₂atmosphere, 10 h).

Styrene, a terminal olefin with no allylic hydrogen, provided

85% selectivity and 80% yield for the styrene oxide product. In

contrast, cyclohexene, which possesses allylic hydrogen, resulted

in high total yields (485%) of the allylic oxidation products of

2-cyclohexen-1-one and cyclohexene-3-(tert-butyl)peroxide. Our

experimental results also showed that a free radical mechanism

is the main pathway for the oxidation of olefins catalyzed by

Ln-MOF-589 (Ln = La, Ce) frameworks.

2-cyclohexen-1-one when TEMPO was inserted into the media

at the beginning and 2 h reaction time (Fig. 14). As shown in

Fig. 14, 2-cyclohexen-1-one and cyclohexene-3-(tert-butyl)peroxide

were the major products while cyclohexene oxide existed as a

minor product, suggesting the involvement of radical species in

the cyclohexene oxidation process.^34,47,48,52Cyclohexene has

allylic hydrogen that is more active than the CQC bond toward

the t-BuOO^ꢃand t-BuO^ꢃradicals, and thus the oxidation reaction

aﬀorded mainly allylic oxidation products. Based on our experi-

mental results and previous reports, the mechanism of cyclo-

hexene oxidation was proposed (Scheme 2).^47,53First, t-BuOO^ꢃ

Author contributions

Y. B. N. Tran: Validation, Formal analysis, Investigation, Data

curation, Writing – original draft. Phuong T. K. Nguyen:

Conceptualization, Methodology, Writing – original draft,

Writing – review & editing, Visualization, Supervision.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

We are grateful to Provost. Dr Bao N. Le and Dr Ai. V. Dao (Duy

Tan University) for supporting our science activities. We thank

Dr Sunhwa Lee (Sungkyunkwan University) for her assistance

with XPS analysis.

Scheme 2 Possible mechanism for the oxidation of cyclohexene cata-

lyzed by Ce-MOF-589.

2100 | New J. Chem., 2021, 45, 2090--2102

View Article Online

Paper

NJC

25 Z. Huang, F. Zhao, L. Fan, W. Zhao, B. Chen, X. Chen, S.-F.

Zhou, J. Xiao and G. Zhan, Mater. Des., 2020, 194, 108881.

26 H. N. Abdelhamid, G. A.-E. Mahmoud and W. Sharmouk,

J. Mater. Chem. B, 2020, 8, 7548–7556.

Notes and references

¨

1 Y. Shi, in Modern Oxidation Methods, ed. J.-E. Backvall,

Wiley-VCH, Weinheim, Second Edition, 2010, ch. 3,

pp. 85–115.

2 P. C. B. Page and T. J. McCarthy, Comprehensive Organic

Synthesis, Pergamon, Oxford, 1991.

27 H. N. Abdelhamid, M. Wilk-Kozubek, A. M. El-Zohry,

´

A. Bermejo Gomez, A. Valiente, B. Martın-Matute, A.-V.

Mudring and X. Zou, Microporous Mesoporous Mater.,

2019, 279, 400–406.

´

3 A. Corma and H. Garcıa, Chem. Rev., 2002, 102, 3837–3892.

4 S. Linic and M. A. Barteau, in Handbook of Heterogeneous

Catalysis, ed. G. Ertl, H. Knozinger, F. Schu¨th and

J. Weitkamp, Wiley-VCH, Weinheim, 2008, pp. 3448–3464.

5 A. Dhakshinamoorthy, A. M. Asiri and H. Garcia, Chem. –

Eur. J., 2016, 22, 8012–8024.

´

28 H. N. Abdelhamid, A. Bermejo-Gomez, B. Martın-Matute

and X. Zou, Microchim. Acta, 2017, 184, 3363–3371.

29 K. Mu¨ller-Buschbaum, The Chemistry of Metal–Organic

Frameworks, Wiley-VCH Verlag GmbH & Co., KGaA, 2016,

ch. 9, pp. 231–270.

¨

6 J. W. Maina, C. Pozo-Gonzalo, L. Kong, J. Schu¨tz, M. Hill and

30 H. T. D. Nguyen, Y. B. N. Tran, H. N. Nguyen, T. C. Nguyen,

´

L. F. Dumee, Mater. Horiz., 2017, 4, 345–361.

´

F. Gandara and P. T. K. Nguyen, Inorg. Chem., 2018, 57,

´

7 J. Gascon, A. Corma, F. Kapteijn and F. X. Llabres i Xamena,

ACS Catal., 2014, 4, 361–378.

13772–13782.

31 P. Cancino, A. Vega, A. Santiago-Portillo, S. Navalon,

8 C. Pagis, M. Ferbinteanu, G. Rothenberg and S. Tanase, ACS

Catal., 2016, 6063–6072.

´

M. Alvaro, P. Aguirre, E. Spodine and H. Garcıa, Catal. Sci.

Technol., 2016, 6, 3727–3736.

9 A. Dhakshinamoorthy, M. Alvaro and H. Garcia, Catal. Sci.

Technol., 2011, 1, 856–867.

32 R. Sen, D. Saha and S. Koner, Catal. Lett., 2012, 142,

124–130.

10 H. Furukawa, K. E. Cordova, M. O’Keeﬀe and O. M. Yaghi,

Science, 2013, 341, 1230444.

11 P. T. K. Nguyen, H. T. D. Nguyen, H. N. Nguyen, C. A.

33 R. Sen, D. K. Hazra, M. Mukherjee and S. Koner, Eur.

J. Inorg. Chem., 2011, 2826–2831.

34 A. Dhakshinamoorthy, M. Alvaro and H. Garcia, ACS Catal.,

2011, 1, 836–840.

´

Trickett, Q. T. Ton, E. Gutierrez-Puebla, M. A. Monge,

´

K. E. Cordova and F. Gandara, ACS Appl. Mater. Interfaces,

35 M. Tonigold, Y. Lu, A. Mavrandonakis, A. Puls, R. Staudt,

2018, 10, 733–744.

¨

J. Mollmer, J. Sauer and D. Volkmer, Chem. – Eur. J., 2011,

´

12 J. Jiang, F. Gandara, Y.-B. Zhang, K. Na, O. M. Yaghi and

17, 8671–8695.

W. G. Klemperer, J. Am. Chem. Soc., 2014, 136, 12844–12847.

13 J. Chen, Y. Li, J. Gu, M. V. Kirillova and A. M. Kirillov, New

J. Chem., 2020, 44, 16082–16091.

14 Y. B. N. Tran, P. T. K. Nguyen, Q. T. Luong and K. D. Nguyen,

Inorg. Chem., 2020, 59, 16747–16759.

36 G. H. Dang, Y. B. N. Tran, T. V. Pham, V. T. Pham, N. T. H.

Luu, H. D. Nguyen, P. T. K. Nguyen, H. T. D. Nguyen and

T. Truong, ChemPlusChem, 2019, 84, 1046–1051.

37 M. Al Kobaisi, S. V. Bhosale, K. Latham, A. M. Raynor and

S. V. Bhosale, Chem. Rev., 2016, 116, 11685–11796.

15 A. Das, N. Anbu, P. Varalakshmi, A. Dhakshinamoorthy and

S. Biswas, New J. Chem., 2020, 44, 10982–10988.

16 H. Li, K. Wang, D. Feng, Y.-P. Chen, W. Verdegaal and

H.-C. Zhou, ChemSusChem, 2016, 9, 2832–2840.

17 K. Leus, Y.-Y. Liu and P. Van Der Voort, Catal. Rev., 2014, 56,

1–56.

¨

38 A. O. Yazaydın, A. I. Benin, S. A. Faheem, P. Jakubczak,

J. J. Low, R. R. Willis and R. Q. Snurr, Chem. Mater., 2009,

21, 1425–1430.

39 J.-H. Noh, R. Patala and R. Meijboom, Appl. Catal., A, 2016,

514, 253–266.

40 S. Sharma, S. Sinha and S. Chand, Ind. Eng. Chem. Res.,

2012, 51, 8806–8814.

41 C. Anandan and P. Bera, Appl. Surf. Sci., 2013, 283,

297–303.

18 J. Jacobsen, A. Ienco, R. D’Amato, F. Costantino and

N. Stock, Dalton Trans., 2020, 49, 16551–16586.

˜

19 P. Cancino, L. Santibanez, C. Stevens, P. Fuentealba,

N. Audebrand, D. Aravena, J. Torres, S. Martinez, C. Kremer

and E. Spodine, New J. Chem., 2019, 43, 11057–11064.

42 R. Dalapati, B. Sakthivel, M. K. Ghosalya, A. Dhakshinamoorthy

and S. Biswas, CrystEngComm, 2017, 19, 5915–5925.

43 D. Yue, D. Zhao, J. Zhang, L. Zhang, K. Jiang, X. Zhang,

Y. Cui, Y. Yang, B. Chen and G. Qian, Chem. Commun., 2017,

53, 11221–11224.

´

20 P. Cancino, V. Paredes-Garcıa, C. Aliaga, P. Aguirre,

D. Aravena and E. Spodine, Catal. Sci. Technol., 2017, 7,

231–242.

21 R. Sen, S. Koner, D. K. Hazra, M. Helliwell and

M. Mukherjee, Eur. J. Inorg. Chem., 2011, 241–248.

22 R. Dalapati, B. Sakthivel, A. Dhakshinamoorthy, A. Buragohain,

A. Bhunia, C. Janiak and S. Biswas, CrystEngComm, 2016, 18,

7855–7864.

44 J. Wu, J. Liang, R. Ma and T. Sasaki, J. Phys. Chem. C, 2015,

119, 26229–26236.

45 J. Zhang, A. V. Biradar, S. Pramanik, T. J. Emge, T. Asefa and

J. Li, Chem. Commun., 2012, 48, 6541–6543.

46 M. Yonemitsu, Y. Tanaka and M. Iwamoto, J. Catal., 1998,

178, 207–213.

´

23 P. Cancino, V. Paredes-Garcıa, P. Aguirre and E. Spodine,

Catal. Sci. Technol., 2014, 4, 2599–2607.

24 L. Fan, K. Wang, K. Xu, Z. Liang, H. Wang, S.-F. Zhou and

G. Zhan, Small, 2020, 16, 2003597.

47 R. Antony, G. L. Tembe, M. Ravindranathan and R. N. Ram,

J. Mol. Catal. A: Chem., 2001, 171, 159–168.

48 W.-J. Sun and E.-Q. Gao, Mol. Catal., 2020, 482, 110746.

New J. Chem., 2021, 45, 2090--2102 | 2101

View Article Online

NJC

Paper

49 H.-F. Yao, Y. Yang, H. Liu, F.-G. Xi and E.-Q. Gao, J. Mol. 53 J. Kim, R. G. Harrison, C. Kim and L. Que, J. Am. Chem. Soc.,

Catal. A: Chem., 2014, 394, 57–65. 1996, 118, 4373–4379.

50 R. Srirambalaji, S. Hong, R. Natarajan, M. Yoon, R. Hota, Y. Kim, 54 U. Neuenschwander, F. Guignard and I. Hermans,

Y. Ho Ko and K. Kim, Chem. Commun., 2012, 48, 11650–11652. ChemSusChem, 2010, 3, 75–84.

51 B. C. Ranu and U. Jana, J. Org. Chem., 1998, 63, 8212–8216. 55 X. Li, D. Ma, B. Cao and Y. Lu, New J. Chem., 2017, 41,

52 T. Bunchuay, R. Ketkaew, P. Chotmongkolsap, T. Chutimasakul, 11619–11625.

J. Kanarat, Y. Tantirungrotechai and J. Tantirungrotechai, Catal. 56 W. Nam, H. J. Kim, S. H. Kim, R. Y. N. Ho and J. S.

Sci. Technol., 2017, 7, 6069–6079.

Valentine, Inorg. Chem., 1996, 35, 1045–1049.

2102 | New J. Chem., 2021, 45, 2090--2102

Article Doi

Lanthanide metal-organic frameworks for catalytic oxidation of olefins

DOI: 10.1039/d0nj05685e

Source and publish data:

Authors:

Article abstract of DOI:10.1039/d0nj05685e

Full text of DOI:10.1039/d0nj05685e

Products guided by the article

R&D Labs maybe for 286-20-4

Relevant to this article

Hot Product