Article abstract of DOI:10.1016/j.catcom.2019.05.006

Based on the acid-base mixed-ligand assembly strategy, a stable Mn(II)-based metal-organic framework (denoted as Mn-MOFs), containing 1-D Mn–O–C rod-shaped chains, was hydrothermally synthesized and structurally characterized. This material was demonstrated to be an efficient heterogeneous catalyst for the decarboxylative sulfonylation of cinnamic acids with sodium benzene sulfinates. Moreover, the Mn-MOF catalyst could be recycled up to six times with the retention of both catalytic activity and crystal structure.

Full text of DOI:10.1016/j.catcom.2019.05.006

CatalysisCommunications127(2019)69–74
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Catalysis Communications
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Short communication
Heterogeneous catalytic decarboxylative sulfonylation of cinnamic acids
with sodium benzene sulfinates over a manganese(II)-based rod-shaped
metal-organic framework catalyst
⁎
Qi-Da Dinga, Jin-Ping Sia, Kun-Lin Huangb, Feng Tiana, Sheng-Chun Chena, , Xue-Jun Fenga,
⁎
Ming-Yang Hea, Qun Chena,
a Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou 213164, China
b College of Chemistry, Chongqing Normal University, Chongqing 401331, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Based on the acid-base mixed-ligand assembly strategy, a stable Mn(II)-based metal-organic framework (denoted
as Mn-MOFs), containing 1-D Mn–O–C rod-shaped chains, was hydrothermally synthesized and structurally
characterized. This material was demonstrated to be an efficient heterogeneous catalyst for the decarboxylative
sulfonylation of cinnamic acids with sodium benzene sulfinates. Moreover, the Mn-MOF catalyst could be re-
cycled up to six times with the retention of both catalytic activity and crystal structure.
Mn(II) MOF
Heterogeneous catalysis
Decarboxylative sulfonylation
Cinnamic acid
Vinyl sulfones
1. Introduction
by post-synthetic modification method, and (iv) other active catalysts
supported or encapsulated inside MOF cavities [17]. Particularly, UMS in
Vinyl sulfones not only occur as important structural scaffolds in
many biologically and medically active compounds [1], but also are the
prevalent molecular fragment for various organic transformations
[2,3]. The development of efficient methods for the synthesis of vinyl
sulfones has attracted much attention in recent years [4–6]. In parti-
cular, transition-metal-catalyzed decarboxylative C–S cross-coupling
reactions have emerged as one of the most powerful synthetic routes
because a variety of carboxylic acids are extremely available raw ma-
terials for chemical synthesis [7–12]. Generally, this type of reaction
proceeds in homogenous systems using transition-metal salts as cata-
lysts, such as Pd(OAc)2 [13], Cu(ClO4)2 [14] and Mn(OAc)2 [15].
However, a major drawback of these homogeneous procedures is the
resulting difficulty associated with separation and recycling of metal
catalysts. To solve these problems, from an economical and sustainable
point of view, developing highly efficient heterogeneous catalysts for
decarboxylative sulfonylation is of great importance.
MOFs can show various well-defined inorganic connectivities, ranging
from discrete zero-dimensional moieties (mono-, di- and polynuclear spe-
cies), one-dimensional inorganic chains, two-dimensional inorganic layers,
even to three-dimensional inorganic hybrids [18]. In recent years, the use
of active UMS with diverse inorganic connectivities toward enhanced
heterogeneous organic transformations have been reported [19,20].
However, in most cases, the inferior thermal and chemical stability of
MOFs leads to the collapse of the framework structure during the catalytic
process. To address this problem, several groups have developed acid-base
mixed-linker systems to construct MOF materials that exhibit higher sta-
bility and catalytic activity over those with one single organic linker
[21,22]. Very recently, we have also shown the application of mixed-linker
MOFs of Cu(II) and Co(II) as robust heterogeneous catalysts for the alcohol
oxidation and cross-dehydrogenative coupling amination reactions
[23,24].
Several studies have been conducted on the utilization of manga-
nese salts and conventional solid-supported manganese oxide materials
for catalytic decarboxylative couplings [4,15,25]. Over the past decade,
Mn(II)-based MOFs have shown great promise as highly efficient het-
erogeneous catalysts for some important organic transformations
[26–28]. In this communication, we used the mixed linkers of 1,4-
naphthalenedicarboxylic acid (1,4-H2NDC) and 1,4-bis(imidazol-1-yl-
methyl)-2,3,5,6-tetrafluorobenenze (Fbix) to synthesize a stable Mn(II)-
Metal-organic frameworks, consisting of organic linkers and metal-
connecting nodes, have recently developed into an important class of
crystalline materials for heterogeneous catalysis [16]. In MOF-based cat-
alytic materials, the active sites might be introduced into MOFs through
four possible ways: (1) unsaturated metal sites (UMS) at the nodes; (2)
active sites embedded within the organic linkers and considered as part of
the framework; (iii) active sites attached to metal nodes or organic linkers
⁎ Corresponding authors.
E-mail addresses: csc@cczu.edu.cn (S.-C. Chen), chenqunjpu@yahoo.com (Q. Chen).
https://doi.org/10.1016/j.catcom.2019.05.006
recibido en 1 febrero 2019; recibido en versión revisada en 2 mayo 2019; aceptado en 7 mayo 2019
Availableonline08May2019
1566-7367/©2019ElsevierB.V.Allrightsreserved.

Q.-D. Ding, et al.
CatalysisCommunications127(2019)69–74
(21.6 mg, 0.1 mmol), Fbix (31.0 mg, 0.1 mmol) and water (7 mL) was
stirred for 20 min at room temperature and then sealed in a 25-mL
Teflon-lined stainless steel container, which was heated at 140 °C for
48 h. After cooling to room temperature, yellow block-shaped crystals
were obtained in ca. 54.2% yield. The crystals were grinded, and wa-
shed with ethanol, and then dried in air, affording the powder used for
the catalytic reactions.
The crystallographic data for Mn-MOF has been deposited as CCDC-
1496990.
2.2. Catalytic reaction
In a typical experiment, cinnamic acid (74.1 mg, 0.5 mmol), sodium
benzenesulfinate (246.2 mg, 1.5 mmol), Mn-MOF (12.7 mg, 3 mol%), KI
(249.0 mg, 3 equiv) and DMSO (4 mL) were taken in a 25-mL three-
necked round-bottom flask. The solution was magnetically stirred for
some hours at 110 °C under air atmosphere. The progress of the reaction
was monitored by high-performance liquid chromatography (Shimadzu
LC-VP) with a UV detector at 274 nm, a Hypersil ODS2 column
(250 mm × 4.6 mm, 5 μm), and a mixture of CH3CN and H2O (v/v: 6:4)
as eluent. The concentration of cinnamic acid and product were cali-
brated by external standard method with standard samples. The reac-
tion solution containing Mn-MOF catalyst was easily separated by fil-
tration, and the catalyst was then washed with DMSO and ethanol and
dried under vacuum.
Fig. 1. Perspective view of the hex-type framework of Mn-MOF.
based rod-shaped MOF [Mn2(1,4-NDC)2(Fbix)]n (Mn-MOF), and ap-
plied it as an active and recyclable catalyst for the decarboxylative
sulfonylation of cinnamic acids with sodium benzene sulfinates.
Moreover, to our knowledge, catalytic decarboxylative sulfonylation
reactions over MOF catalysts have not been mentioned in the literature.
2. Experimental
3. Results and discussion
2.1. Catalyst synthesis
3.1. Synthesis and characterization of catalyst
Both 1,4-H2NDC and Fbix are insoluble in water at room
A
mixture of MnCl2∙4H2O (39.6 mg, 0.2 mmol), 1,4-H2NDC
Table 1
Optimization of the reaction conditionsa.
Entry
Catalyst
Additive
Solvent
Yield (%)b
1
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
Mn-MOF
None
KI
DMSO
DMA
93
81
64
80
72
16
18
28
68
31
Trace
Trace
46
73
8
2
KI
3
KI
DCE
4
KI
DMF
5
KI
NMP
6
KI
H2O
7
KI
EtOH
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
8
None
NaI
NH4I
I2
9
10
11
12
13
14
15
16c
17d
18e
19f
K2CO3
KCl
KBr
KI
Mn-ZSM-5
Mn/SiO2
Mn/Sil-1-10-2
Mn-MOF
KI
28
35
32
15
KI
KI
KI
a
Reaction conditions: cinnamic acid (0.5 mmol), sodium benzenesulfinate (1.5 mmol), additive (3.0 equiv), catalyst (12.7 mg, 3 mol% Mn), solvent (4.0 mL),
under air.
b
c
d
e
f
Based on LC analysis.
With 105.6 mg Mn-ZSM-5 (3 mol% Mn).
With 41.2 mg Mn/SiO2 (3 mol% Mn).
With 41.2 mg Mn/Sil-1-10-2 (3 mol% Mn).
Under N2.
70

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CatalysisCommunications127(2019)69–74
Table 2
Substrate scope for the synthesis of vinyl sulfonesa, b
.
a
Reaction conditions: 1 (0.5 mmol), 2 (1.5 mmol), KI (1.5 mmol), DMSO (4 mL), Mn-MOF (12.7 mg, 3 mol% Mn), 110 °C, 9 h,
b
open air. The yields are of materials isolated by column chromatography.
71

Q.-D. Ding, et al.
CatalysisCommunications127(2019)69–74
temperature. Mn-MOF was prepared under hydrothermal conditions in
a moderate yield. It should be pointed out that only amorphous powder
was obtained under similar reaction conditions when manganese(II)
salts including Mn(OAc)2∙2H2O and MnSO4∙H2O.
Single-crystal X-ray diffraction analysis revealed that Mn-MOF
crystallizes in the monoclinic space group P21/c and the asymmetric
unit contains two Mn(II) ions (Mn1 and Mn2), two 1,4-NDC anions, and
one Fbix ligand. Both Mn1 and Mn2 are five-coordinated by four
oxygen atoms from four 1,4-NDC ligands with the Mn–O distances in
the range of 2.036(2)–2.168(2) Å and one nitrogen atom from Fbix li-
gand with the Mn–N distances of 2.187(2) and 2.236 Å, exhibiting a
distorted square-pyramid geometry (Fig. S1). Each 1,4-NDC ligand is
linked to four Mn(II) ions with two carboxylate groups adopting the μ2-
η1:η1-syn-syn-bridging mode. Adjacent Mn(II) ions are linked in se-
quence by carboxylate groups of 1,4-NDC, forming an 1-D Mn–O–C rod-
shaped chains along the c-axis (Fig. S2). Each chain links four neigh-
boring chains through the 1,4-NDC linkers to generate a 3-D sub fra-
mework (Fig. S3). The Fbix ligand exhibits a trans configuration and
connects the rod-shaped chains together with 1,4-NDC to form the final
3-D framework with the hex net (Figs. 1 and S4) [29].
Fig. 2. Catalyst recycling studies.
catalyst is the reagent molar ratio. A large excess of sodium benzene-
sulfinate should be required for the coupling. Fig. S10 shows the de-
pendence of the yield on the effect of reagent molar ratio. At 3 mol%
Mn-MOF loadings, higher yield was achieved at 110 °C when 3
equivalents of sodium benzenesulfinate were used, while utilization of
lower amounts of sodium benzenesulfinate led to a obvious decrease in
reaction efficiency.
Powder X-ray diffraction (PXRD) patterns (Fig. S5) confirmed the
phase purity of the as-synthesized Mn-MOF. The thermal stability was
investigated by the combination of TG analysis and temperature-de-
pendent PXRD patterns (Figs. S6 and S7), suggesting that Mn-MOF can
retain its structure in air up to 300 °C. Moreover, after the bulk samples
were suspended in refluxing water, ethanol, dichloroethane or hot or-
ganic solvents including DMF, NMP and DMSO at 120 °C for 24 h, Mn-
MOF could remain intact without loss of crystallinity (Fig. S8).
Subsequently, the substrate scope of the Mn-MOF-catalyzed dec-
arboxylative sulfonylation reaction was also explored with diverse
substituted cinnamic acids and sodium benzenesulfinates under the
above-mentioned optimal conditions (see Table 2). The Mn-MOF cata-
lyst was found to efficiently catalyze a range of cinnamic acids and
several sodium benzenesulfinates, and the products were isolated in
yields ranging from 42% to 98%. Cinnamic acid derivatives bearing
electron-donating functional groups afforded better yields than the
substrates with electron-withdrawing substituents. Moreover, sodium
benzenesulfinates with 4-H, 4-Me, 4-F and 4-Cl groups substituted on
phenyl rings proceeded smoothly to give the desired vinyl sulfone
products. Between ortho- and meta-methyl or chloride substituents, no
obvious negative steric effect was found. In addition, aliphatic sub-
strates such as 3-methyl-2-butenoic acid and trans-2-hexenoic acid as
well as sodium methane sulfinate have also been examined for the
catalytic system. However, no desired products were obtained.
3.2. Catalytic performance
The decarboxylative sulfonylation of cinnamic acid with sodium
benzene sulfinate was selected as a model reaction using Mn-MOF as
heterogeneous catalyst to study the reaction conditions. First,
a
screening of different solvents revealed that aprotic polar solvents gave
higher yields, where DMSO was found to be the best (Table 1, entries
1–7). On the basis of the Mn(OAc)2-catalyzed decarboxylative sulfo-
nylation reported by Deng et al. [15,30–32], the iodine additive is
crucial for this reaction. Then, influence of various reagents on the
reaction was investigated. In the absence of the iodine reagent, the
reaction gave a low yield (entry 8). Significantly enhanced yield was
observed in the presence of KI, and addition of other additives including
I2 and K2CO3 failed to give any positive effect (entries 11 and 12).
Furthermore, when KCl and KBr were employed instead of KI, the re-
actions could proceed smoothly to afford the corresponding product in
moderate to good yields (entries 13 and 14). The results suggested that
iodide anion might act as soft Lewis base to capture soft Lewis acid
carbon cation in this transformation, giving the corresponding vinyl
sulfone products with high yields, which is similar to that observed in
the heterogeneous catalytic process reported by Guo et al. [8]. It was
also found that the reaction in the absence of Mn-MOF catalyst gave
only trace product (entry 15), while the yield was dramatically im-
proved to 93% when 3 mol% Mn-MOF was added to the reaction
mixture. In our previous work, Cu-doped zeolites have been developed
for decarboxylative coupling reactions [33]. For comparison, Mn-con-
taining heterogeneous catalysts including Mn-ZSM-5, Mn/SiO2 and Mn/
Sil-1-10-2 in the reaction system were far less efficient (entries 16–18).
Similar to the homogenous Mn(II)-catalyzed system [15], the presence
of air atmosphere was beneficial to this transformation. When the re-
action was conducted under N2 atmosphere, yield was significantly
diminished (entry 19).
3.3. Catalyst heterogeneity and reusability
To verify the heterogeneous nature of the Mn-MOF-catalyzed reac-
tion process, the leaching experiments were carried out (Fig. S9). After
removing the solid catalyst, it was found that no further conversion of
cinnamic acid was detected even after 8 h. Moreover, examination by
ICP analysis of the filtrate indicated a negligible amounts (< 1 ppm) of
the manganese. In recycling tests, before the catalyst was reused, the
Mn-MOF catalyst was collected by centrifugation, washed with DMSO
and ethanol, and dried at 60 °C under vacuum in 12 h. The results re-
vealed that the recovered Mn-MOF catalyst could almost maintain its
high activity with no decrease after six consecutive cycles (Fig. 2).
Furthermore, the PXRD pattern of 6th used catalyst indicated that the
Mn-MOF could retain its crystallinity (Fig. S10).
3.4. Proposed mechanism
To understand the reaction pathway better, some control experi-
ments were carried out (Scheme 1). The reaction of 1a with 2a was
conducted under the standard reaction conditions in the presence of
radical scavengers, including 2,6-di-tert-butyl-4-methylphenol (BHT)
and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) (Scheme 1a and b).
BHT was found to suppress the reaction while TEMPO totally stopped
the reaction, which implied that a radical pathway should be involved.
Next, when styrene was employed as a substrate in place of 1a (Scheme
1c), no 3a was observed. The result suggested that styrene is not an
intermediate in the present reaction. Furthermore, it was also found
Fig. S9 shows the dependence of the yield on the effect of reaction
temperature. Indeed, the yield markedly increased at higher tempera-
ture and 110 °C was found to be a relatively optimized temperature,
where the reaction could afford 93% yield after 9 h. Another factor that
should be considered for the cross-coupling reaction over the Mn-MOF
72

Q.-D. Ding, et al.
CatalysisCommunications127(2019)69–74
Scheme 1. Control experiments.
that the homogeneous Mn(II) catalysts (Scheme 1d and f)and Mn(III)
species (Scheme 1e and g) showed comparable activity, suggesting that
the true catalyst might be the Mn(III) species [15]. Comparison of
catalytic activities of the Mn(II) and Mn(III) catalysts in the model re-
action with that of Mn-MOF revealed that Mn-MOF exhibits higher
performance, which may be related to the characteristic of the Mn-
based rod-shaped active sites [34]. The oxidation state of manganese
species in the fresh Mn-MOF and the samples of different catalytic cy-
cles have been analyzed by X-ray photoelectron spectroscopy (XPS)
(Fig. S14). The observation of the Mn 2p3/2 peak at 643.20 eV de-
monstrated no change in the oxidizing state for manganese, further
implying Mn-MOF is stable during the reaction process. To detect the
73

Q.-D. Ding, et al.
CatalysisCommunications127(2019)69–74
Institutions (PAPD), the Advanced Catalytic and Green Manufacturing
Collaborative Innovation Center, Changzhou University and Jiangsu
Key Laboratory of Advanced Catalytic Materials and Technology
(ZZZD201807 and BM2012110).
MOF
Mn(II)
COOH
COOMn(II) MOF
Ph
Ph
1a
C
O2
KI
I2
Appendix A. Supplementary data
DMSO
PhSO2Na
PhSO2I
PhSO2
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.catcom.2019.05.006.
2a
A
B
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MOF
Mn(II)
COO
COOMn(II) MOF
O2SPh
O2SPh
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