An Uncommon Carboxyl-Decorated Metal–Organic Framework with Selective Gas Adsorption and Catalytic Conversion of CO2

Article abstract of DOI:10.1002/chem.201704027

A new three-dimensional (3D) framework, [Ni(btzip)(H₂btzip)]?2 DMF?2 H₂O (1) (H₂btzip=4,6-bis(triazol-1-yl)isophthalic acid) as an acidic heterogeneous catalyst was constructed by the reaction of nickel wire and a triazolyl-carboxyl linker. Framework 1 possesses intersected 2D channels decorated by free COOH groups and uncoordinated triazolyl N atoms, leading to not only high CO₂ and C₂H₆ adsorption capacity but also significant selective capture for CO₂ and C₂H₆ over CH₄ and CO in 273–333 K. Moreover, 1 reveals chemical stability toward water. Grand Canonical Monte Carlo simulations confirmed the multiple CO₂- and C₂H₆-philic sites. As a result of the presence of accessible Br?nsted acidic COOH groups in the channels, the activated framework demonstrates highly efficient catalytic activity in the cycloaddition reaction of CO₂ with propylene oxide/4-chloromethyl-1,3-dioxolan-2-one/3-butoxy-1,2-epoxypropane into cyclic carbonates.

Full text of DOI:10.1002/chem.201704027

A Journal of
Accepted Article
Title: An Uncommon Carboxyl-Decorated MOF with Selective Gas
Adsorption and Catalytic Conversion of CO2
Authors: Lei Hou, Yong-Zhi Li, Hai-Hua Wang, Hong-Yun Yang, Yao-
Yu Wang, and Zhonghua Zhu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201704027
Link to VoR: http://dx.doi.org/10.1002/chem.201704027
Supported by

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
An Uncommon Carboxyl-Decorated MOF with Selective Gas
Adsorption and Catalytic Conversion of CO2
Yong-Zhi Li,[a] Hai-Hua Wang,[a] Hong-Yun Yang,[a] Lei Hou,*[a] Yao-Yu Wang,[a] and Zhonghua Zhu[b]
Abstract:
A
new
three-dimensional
(3D)
framework,
the catalytic activity of MOFs, which serve not only as CO2-binding
sites but also as Lewis and/or Brønsted acidic catalytic sites.[21-32]
Notably, in these MOF catalysts, major catalytic sites are Lewis acidic
OMSs, which are generated via the removal of coordinated solvents at
high temperatures, however, the harsh activated conditions usually lead
to the framework incompletement in a degree. In contrast, the
deliberate embedding of Brønsted acidic sites in MOFs is an alternative
and worth anticipating approach to achieve the capture of CO2 and its
catalytic conversion with epoxides, whereas the related reports were
rarely documented.[28-32] Therefore, the fabrication of MOFs decorated
by Brønsted acidic catalytic sites is an emergency of requirement for
the application of CO2 capture and conversion.
[Ni(btzip)(H2btzip)]·2DMF·2H2O (1) (H2btzip
=
4,6-bis(triazol-1-
yl)isophthalic acid) as an acidic heterogeneous catalyst was
constructed by the reaction of nickel wire and a triazolyl-carboxyl
linker. 1 possesses intersected 2D channels decorated by free –
COOH groups and uncoordinated triazoly N atoms, leading to not
only high CO2 and C2H6 adsorption capacity but also significantly
selective capture for CO2 and C2H6 over CH4 and CO in 273-333 K.
Moreover, 1 reveals the chemical stability toward water. Grand
Canonical Monte Carlo simulations confirmed the multiple CO2- and
C2H6-philic sites. As a result of the presence of accessible Brønsted
acidic –COOH groups in channels, the activated framework
demonstrates highly efficient catalytic activity in the cycloaddition
reaction of CO2 with propylene oxide/4-cloromethyl-1,3-dioxolan-2-
one/3-butoxy-1,2-epoxypropane into cyclic carbonates.
The selection of the organic ligand is critical for the assembly of
desired functional MOFs. The carboxylate ligands and azolate ligands
represent the most classic ligands due to the multivariate coordinated
modes for the former and the rigid coordinated bonds for the latter with
various metal ions.[33] Thus
a
symmetrical 4,6-bis(triazol-1-
yl)isophthalic acid (H2btzip) ligand combining the advantages of
carboxylate and azolate groups has been designed, which not only
tends to form stable porous MOFs but also facilitates the adsorption for
CO2 due to the existence of multiple Lewis basic nitrogen atoms.
Herein, the reaction of nickel wire and H2btzip under solvothermal
condition afforded a highly porous three-dimensional (3D) MOF,
[Ni(btzip)(H2btzip)]·2DMF·2H2O (1). 1 exhibits good stability toward
water and possesses channels decorated by uncoordinated N atoms and
free Brønsted acidic –COOH catalytic sites. As a result, 1 demonstrates
high uptakes for CO2 and C2H6, significant adsorption selectivities of
CO2/CH4, CO2/CO, and C2H6/CH4 as well as highly efficient catalysis
for the reaction of CO2 with propylene oxide/4-cloromethyl-1,3-
dioxolan-2-one/3-butoxy-1,2-epoxypropane into cyclic carbonates.
Introduction
The rapid development of petrol and automobile industries has brought
about massive accumulating of CO2 in atmosphere and the large-scale
consumption of natural gas, which is causing severe climate problems
occurred. The exploitation of efficient CO2 capture technologies has
been intensively focused.[1,2] In this context, carbon capture and
sequestration (CCS) has been suggested as an effective way to solve
this issue.[3] Furthermore, the captured CO2 as a feedstock is transferred
into useful chemicals by chemical fixation would be highly
meaningful,[4-6] and is also recognized to be environmentally benign.[7,8]
According to atomic economy, the cycloaddition of CO2 with an
epoxide under the help of catalysts to produce cyclic carbonates, the
important reagents in industry, is quite desired, and does not generate
any side products as well.
Endowed with regular structures, high porosity, modifiable porous
surface, metal-organic frameworks (MOFs) might be promising porous
materials for selective gas adsorption and effective heterogeneous
catalysts, including the adsorption and separation of small molecules
such as N2, H2, CO and hydrocarbons (CH4 and C2H6)[9-12] as well as
CO2 adsorption and catalysis.[13-18] Recently, some excellent examples
have witnessed the success of MOFs as heterogeneous catalysts in the
reaction of CO2 with epoxides.[19,20] Wherein the existence of accessible
open metal sites (OMSs) and/or acidic groups in pores are crucial for
Results and Discussion
Synthesis. Differing from the usually solvothermal syntheses of MOFs
that employ metal salts as the metal ion source, the nickel wire
(diameter of about 0.4 mm) is required for the formation of complex 1
(Figure 1). In contrast, under the similar conditions the nickel(II) salts
as direct reactants, such as Ni(Ac)2, NiCl2, Ni(NO3)2 and NiSO4, the
unknown flocky precipitates were produced (Figure S2). The slight
acidity of solution is necessary for the formation of 1, which favorably
activates the surface of nickel wire, and leading to that the sheet-like
crystal of 1 is in-situ generated and adhered on the nickel wire. This
result suggests the low concentration of Ni2+ ions is inevitable for the
formation of 1, and the process is kinetically controlled. In addition, 1
can also be prepared by using nickel foam (sizes of 1 × 1 cm2,
thickness of 2 mm), but the yield is slightly less.
Crystal Structure. Complex 1 with the orthorhombic space group
Pbcm consists of one Ni2+ ion, half of deprotonated btzip, and half of
undeprotonated H2btzip in the asymmetric unit (Table S1). The Ni2+
ion with a distorted octahedral coordination environment is coordinated
by four triazolyl N atoms and two carboxylate O atoms (Ni-N =
2.081(3) and 2.102(3) Å , Ni-O = 2.080(2) Å ) from two H2btzip and
[a]
Y.-Z. Li, Dr. H.-H. Wang, H.-Y. Yang, Prof. L. Hou, Y.-Y. Wang
Key Laboratory of Synthetic and Natural Functional Molecule
Chemistry of the Ministry of Education, Shaanxi Key Laboratory of
Physico-Inorganic Chemistry, College of Chemistry & Materials
Science, Northwest University
Xi'an 710069, P. R. China
E-mail: lhou2009@nwu.edu.cn
[b]
Prof. Z. Zhu
School of Chemical Engineering, The University of Queensland
Brisbane 4072, Australia
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/****.*********.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
3D framework (Figures 3b and c). The framework along the a and b
axes contains intersected channels with the respective open sizes of
about 5.0 × 3.2 and 5.9 × 4.9 Ǻ2 (excluding van der Walls radii of the
atoms) and the solvent-free void of 39.2%.[34] The walls of channels are
occupied by free –COOH groups, uncoordinated triazolyl N atoms and
phenyl units of the ligands. The Ni2+ ion can be topologically
designated as a 6-connected node, while H2btzip and btzip can be
simplified as 2-connected and 4-connected nodes, respectively. So 1
forms a binodal (4,6)-connected fsc topology with the point symbol of
(44·6 2)(44·6 10·8) by Topos (Figure 3d).[35]
PXRD and TGA. The phase purity of the experimental sample of 1
was demonstrated by the coincident PXRD patterns between the
measured and the simulated from single crystal data (Figure S3). Under
a N2 atmosphere, 1 releases all H2O and DMF guest molecules below
230 °C with a weight loss of 21.5% (calcd. 21.7%), then is
decomposed (Figure S4). The guest-free framework 1a was gained by
the exchange of 1 in CH3OH for 72 h and then heated at 160 °C under
vacuum for 4 h. PXRD illustrated the structural intactness of 1a
(Figure S3).
Figure 1. Photos of crystals of 1 in-situ formed on the nickel wire.
Sorption properties. As 1a possesses intersected pores decorated by –
COOH and triazolyl groups, the porosity was assessed by the gas
adsorption of N2, CO2, CH4, CO and C2H6. 1a reveals a type-I sorption
isotherm for N2 at 77 K (Figure 4a). The fitted Langmuir and BET
surface areas are 956 and 731 m2g-1, respectively, and the pore size
region of 5.0-7.4 Å is available on the basis of Horvath-Kawazoe
model (Figure S5), agreeing with the crystal structure. The type-I
sorption isotherms were also found in 1a for CO2, CH4, CO and C2H6
at 195 K, with the adsorption amounts according a sequence of CO2 >
C2H6 > CH4 > CO (Figure 4a). The relatively higher amounts for CO2
and C2H6 than CH4 and CO allow us to further estimate the potential
gas separation application in CO2/CH4, CO2/CO and C2H6/CH4 at
ambient temperatures.
Figure 2. Coordination environment of Ni2+ ion in 1. Symmetry codes: #1: 1-x, 1-y, 1-
z; #2: -x, 1-y, 1-z; #3: x-1, y, z; #4 x, y, 0.5-z; #5: x, 1.5-y, 1-z.
Figure 3. a) 2D layer formed by btzip and Ni2+ ions, b) and c) 3D framework viewed
along the a and b axes, respectively, and d) fsc topology of 1.
four btzip (Figure 2, Table S2). H2btzip in 1 has a mirror that is parallel
to the ab crystallographic plane and passes through the 2,5-positioned
two C atoms of phenyl ring, while the same positions in btzip is
threaded by a two-fold symmetry axis. The ligands exist two
coordination modes: one btzip links four Ni2+ ions through two
carboxylate O atoms and two triazolyl N atoms; one H2btzip connects
two Ni2+ ions by two triazolyl N atoms, leaving two uncoordinated –
COOH groups. The connection of btzip with Ni2+ ions affords a
square-grid layer parallel to the ab crystallographic plane (Figure 3a).
The interlayer Ni2+ ions along the c axis are bridged by H2btzip to get a
Figure 4. Sorption isotherms of 1a at cryogenic temperature (a) and around room
temperatures (b and c), and d) a comparison of adsorption amounts at 100 kPa and
different temperatures.
At 273, 298, 313 and 333 K, 1a all reveals significant adsorptions
for CO2 and C2H6 but low uptakes for CH4 and CO, as shown in
Figures 4b-d. At 298 K and 100 kPa, the CO2 loading in 1a is 106.4
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
cm3 g-1 (20.9 wt%), which is comparable with the value reported in a
N-rich zinc-terazolate MOF (22.0 wt%),[36] but is superior to those
reported in major MOFs, such as the well-known Cu2(COO)4
paddlewheel-based MOFs including NOTT-125 (18.9 wt%),[37]
Cu3(CPEIP)2(H2O)3 (15.3 wt%),[38] MFM-130 (11.6 wt%),[39] JUC-141
(10.1 wt%),[40]and [Cu3(ATTCA)2(H2O)3] (9.7 wt%).[41] It is noted that
compared to the gas adsorption performance of MOFs usually done at
298 K, sporadic examples were investigated at the broader temperature
regions, such as 313 and 333 K,[42-52] though which are closer to the
practical temperatures of flue gas in post-combustion process.
Remarkably, at 313 and 333 K, the uptakes of CO2 in 1a are 86.6 (17.0
wt%) and 67.0 (13.2 wt%) cm3 g-1, respectively, at 100 kPa, which list
among the best values of CO2 uptake in MOFs recorded at similar
temperatures (Table 1). In addition, when 1 was soaked in water for 24
h at room temperature and then desolvated by vacuum heating, the
resultant sample shows almost no change of adsorption amount for
CO2 at 298 K (Figure S6), demonstrating the good chemical stability
toward water, which is one of important indicator for MOFs
application.
Owing to the obvious distinction in adsorption amounts, the
selectivities of CO2 over CH4 and CO for CO2-CH4 and CO2-CO
mixtures were predicted by the ideal adsorbed solution theory (IAST)
at 298, 313 and 333 K, respectively (Figure S7). As shown in Figure 5a,
the CO2/CH4 selectivity of 1a at 298 K rises from 10.2 to 13.9 with the
CO2 concentration increased from 5% to 95%. For the CO2-CH4
mixtures with 5% and 50% CO2 ratios, the common compositions of
landfill gas and natural gas, respectively, the corresponding CO2/CH4
selectivities are 10.2 and 12.2, preceding most of the reported MOFs
with good CO2/CH4 selectivity at similar conditions (Tables S3 and S5).
Notably, at the higher temperatures of 313 and 333 K, the CO2/CH4
selectivity in 1a still approaches about 7 in the CO2 concentration range
of 5%-95%. So 1a could be a candidate applied for the arresting of
CO2 from such as natural gas and landfill gas. In addition, for the CO2-
CO mixture, 1a also exhibits more significant CO2/CO selectivity at
298, 313 and 333 K, the values changed from 22.8 to 46.4, 19.9 to 23.6,
and 15.9 to 15.0, respectively, with the CO2 concentrations increased
from 5% to 95% (Figure 5b). This remarkable selectivity enables 1a
very useful to trap CO2 from a verity of gases containing CO.
Table 1. The comparison of CO2 adsorption amounts in 1a and reported MOFs at 313-
333 K and 100 kPa.
MOFs
n (mmol g-1)
T (K) Ref.
MOF-74(Mg)
[Ni(btzip)(H2btzip)], (1a)
bio-MOF-11
8.01
3.86
2.99
3.57
313
313
333
313
42
this work
43
44
44
2.81
1.61
315
333
Cu3(BTC)2
2.78
314
44
Cr3(BTC)2
1.62
2.50
1.37
333
313
333
44
29
29
[Co2(tzpa)(OH)(H2O)2]
2.46
313
45
[Mn2(Hcbptz)2(Cl)(H2O)]Cl
1.75
333
46
bio-MOF-12
SIFSIX-3-Zn
2.46
2.40
2.10
313
308
328
46
46
46
Figure 5. Sorption selectivity of CO2/CH4 (a), CO2/CO (b) and C2H6/CH4 (c) in 1a at
298, 313 and 333 K with various molar ratios in binary mixtures. d) Adsorption heat
of 1a for different gases.
2.41
1.47
2.28
1.47
313
333
313
333
44
44
44
44
[Ru3(BTC)2][BTC]0.5
In contrast to the low loading of CH4 at ambient temperature, 1a has
more uptakes for C2H6, and the adsorption amounts at 100 kPa are
106.8, 88.9, 75.90 and 59.18 cm3 g-1 at 273, 298, 313 and 333 K,
respectively (Figure 4b). These amounts are relatively high compared
to the results reported in most MOFs reported at the similar conditions
(Table S4 and S5), such as UTSA-33,[53] BIF-24,[54] BUT-70A and
BUT-70B.[55] The C2H6/CH4 selectivities of 1a were further calculated
at 298, 313 and 333 K, which display great separation values of 22.3 to
20.5, 15.1 to 12.1 and 11.8 to 9.7, respectively (Figure 5c), with the
various contents of C2H6 from 5% to 95%. The selectivity of 20.6 at
298 K for equimolar C2H6-CH4 mixture is superior to that of Fe-MOF-
74 (18),[56] JXNU-4(14.6),[57] 1-mim (~12),[58] Mg-MOF-74 (7),[56] and
ZJU-48a (6).[59] These facts highlight 1a as a promising material for
selective fractionation of the light hydrocarbons (C2H6/CH4).
Ni3(BTC)2(Me2NH)2(H2O)
1.75
314
44
Mo3(BTC)2(DMF)0.5
1.08
1.66
1.64
1.36
1.35
1.25
1.20
1.13
1.0
333
313
313
313
313
313
313
44
47
43
47
48
47
49
TEA@bio-MOF-1
bio-MOF-13
TBA@bio-MOF-1
[Co8.5(μ4-O)(bpdc)3(bpz)3(Hbpz)3]
bio-MOF-1
IRMOF-3
MOF-5
MIL-101(Cr)
UTSA-16
313.7 50
319
333
313
313
51
52
42
42
0.91
0.83
0.81
Be12(OH)12(BTB)4
bio-MOF-14
The significant selectivity of 1a for CO2 over CH4 and CO as well as
C2H6 over CH4 can be mainly attributed to the incorporated active sites
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
including free –COOH groups and uncoordinated triazolyl N atoms in
the framework, which are exposed on the porous walls, giving rise to a
highly polar framework. Consequently, the stronger interactions exist
between the framework and CO2 or C2H6 than CH4 or CO because of
larger quadrupole moment and higher polarizability of CO2 and C2H6
relative to CH4 and CO (Quadrupole moment (×10-26 esu m2): CO2,
4.30; C2H6, 0.65; CH4, 0; CO, 2.50. Polarizability (×10-25 cm3): CO2,
29.1; C2H6, 44.5; CH4, 25.9; CO, 19.5).[60] The isosteric heats of
adsorption (Qst) of CO2, C2H6, CH4 and CO were calculated based on
the adsorption isotherms at 273, 298 and 313 K (Figures S8-S11). In
overall pressure region, 1a possesses the high Qst for CO2 (27.6-30.1 kJ
mol-1) and C2H6 (30.3-35.2 kJ mol-1), which greatly outperform the
values for CH4 (16.0-16.5 kJ mol-1) and CO (15.5-22.1 kJ mol-1)
(Figure 5d), agreeing well with the difference in the adsorption
amounts for these gases.
C-H···O (H···O = 2.518-2.891 Å ) and C-H···N (H···O = 2.536-2.573 Å )
hydrogen bonds simultaneously (Figure 7b). C2H6-III is sandwhiched
by two H2L and is fixed by four triazolyl units through C-H···N (H···N
= 2.806-3.209 Å ) hydrogen bonds (Figure 7c). Resembling the
situation of CO2, the existence of multiple binding sites in 1a is
responsible for significant C2H6 uptake.
GCMC simulations. The interactions between the framework and CO2
were researched by GCMC simulations (Supporting Information). At
298 K and 100 kPa, four kinds of main CO2 molecules were
distinguished in 1a. CO2-I and CO2-II locate at the middle of two
H2btzip, and are also parallel to the planes of them (Figure 6a). For
CO2-I, the electropositive C atom attracts the electronegative N and O
atoms from one triazolyl group and one free –COOH in one H2btzip,
respectively, in which the C···N (3.195 and 3.334 Å ) and C···O (3.249
Å ) distances approximate with the sum of van der Waals radii of C
(1.70 Å ) and N (1.55 Å ) or O (1.52 Å ) atoms. One O atom in CO2-I
forms a pair of C-H···O (H···O = 2.642 and 2.832 Å ) hydrogen bonds
with two triazolyl –CH groups, while the other O atom in CO2-I forms
strong C···O (C···O = 2.999 Å ) interaction with one phenyl C atom. For
CO2-II, the C atom interacts with two O atoms (C···O = 3.425 and
3.602 Å ) of two free –COOH in two H2btzip, while two O atoms are
involved in C···O (C···O =3.443 Å ) contacts with one phenyl C atom
and C-H···O hydrogen bond (H···O = 2.673 Å ) with one triazolyl –CH
group, respectively. The C atom in CO2-III is fixed by one carboxylic
acid O atom (C···O = 3.023 Å ) and one uncoordinated triazolyl N atom
(C···N = 3.593 Å ), while two O atoms in CO2-III are free (Figure 6b).
Similar to CO2-II, the C atom in CO2-IV also interacts with two
uncoordinated O atoms (C···O = 2.908 and 3.403 Å ), but differently,
which are from one coordinated carboxylate of btzip and one free –
COOH of H2btzip, respectively (Figure 6c). Meanwhile, one O atom in
CO2-IV also contacts with the frameworks through C···O (C···N =3.315
Å ) and C-H···O (H···O = 2.779 Å ) interactions.
The simulation identified a variety of adsorption sites in 1a, such as
free -COOH, uncoordinated carboxylate O atoms and uncoordinated
triazolyl N atoms, which play a decisive role for high CO2 loading.
Notably, three CO2-I, CO2-II and CO2-III molecules with a T-shaped
arrangement are confined in narrow voids and further aggregated by
C···O contacts (3.074-3.524 Å ) between the O atom in one CO2 and the
C atom in other CO2,[61] affording an uncommon cyclic trimer (Figure
6d), which was unobserved in MOFs.
The framework-C2H6 interactions were also distinguished, which
reveals three different locations of C2H6 molecules existed at 100 kPa.
C2H6-I and C2H6-II are close to two free –COOH groups, but which are
from two H2btzip and one H2btzip, respectively. For C2H6-I, the two –
CH3 groups are hydrogen-bonded to carboxyl O atoms (H···O = 2.557-
2.706 Å ) and uncoordinated triazolyl N (H···N = 2.499 and 2.955 Å )
atoms (Figure 7a), respectively, while these groups in C2H6-II form the
Figure 6. Interactions between the framework and CO2 molecules (a, b and c), and a
cyclic trimer generated by three CO2 molecules (d).
Figure 7. Interactions between the framework and C2H6 molecules: a) C2H6-I, b)
C2H6-II, and c) C2H6-III.
Catalytic Cycloaddition of CO2 and Epoxides. Besides the CO2
capture, MOFs have been utilized to serve as heterogeneous acidic
catalysts for chemical conversion of CO2 into cyclic carbonates,
wherein the major catalytic sites result from the Lewis acidic OMSs
and/or Brønsted acidic groups. However, for this CO2 conversion
reaction, the MOF catalysis that contains the Brønsted acidic –COOH
groups was only reported in one 1D coordinated polymer.[28] This fact
results from the preferential coordination of carboxyl with metal ions
during the assembly of MOFs. The unique accessible –COOH sites in
the pores of 1a provide us a scope to carry out the catalytic experiment.
We selected relatively mild conditions (Scheme 1, 0.1 MPa and 25 °C)
in the presence of TBAB as the cocatalyst to access the catalytic ability
of 1a for the reaction of CO2 with propylene oxide (PO), the obtained
9.0% yield of product indicates the low activity of 1a (Table 2, entry 3).
However, the catalytic experiments conducted at 2.0 MPa and 80 °C
for 4 h with 1a and TBAB as co-catalysts afforded high catalytic
efficiency for CO2 and PO transformation into propylene carbonate
with a yield of 98.9% (Table 2, entry 4), which outperforms the
corresponding values reported in some MOFs at the similar
conditions.[15,22,62] In addition, CO2 cycloaddition with epoxides
substituted with different functional groups has also been tested over
1a. With an increase of the molecular sizes of epoxide substrates, the
yield of formation of cyclic carbonates decreased at different degree.
The yields of 4-cloromethyl-1,3-dioxolan-2-one, 4-bromomethyl-1,3-
dioxolan-2-one, 3-butoxy-1,2-propylene carbonate and styrene
carbonate were 98.3%, 83.1%, 90.9% and 40.0%, respectively (Table 2,
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
entries 5-8). This could be caused by the hindrance effect of different
epoxides and corresponding products with large sizes, which slows the
diffusion of reactants. This catalytic capability of the self-supported Ni
MOF catalyst can be compared to that of other known MOFs-based
heterogenerous catalysts for the cycloaddition reaction of CO2 to
epoxides (Table S6). In contrast, the individual catalytic efficiency of
1a or TBAB for PO under 2.0 MPa and 80 °C is very low (entries 1
and 2).
final ring-closing step, the alkyl carbonate anion is converted into the
cyclic carbonate, and simultaneously, TBAB is recycled.
Conclusions
In summary, employing a triazolyl-carboxyl bifunctional ligands, we
have constructed a new MOF through an scarcely adopted synthesis
method of replacing the conventional nickel(II) salt with nickel wire.
The constructed MOF reveals good chemical stability in water and also
possesses intersected open channels decorated by the CO2- and C2H6-
binding sites of free carboxyl groups together with uncoordinated
triazolyl groups, which lead to not only high CO2 and C2H6 uptakes but
also remarkable selectivelies of CO2/CH4, CO2/CO, and C2H6/CH4.
This material would be a candidate for CO2 capture from natural gas
and landfill gas, as well as a promising application for the separation of
CO2-CO mixture or C2H6-CH4 light hydrocarbons. In addition, the
existing accessible carboxyl groups as Brønsted acidic sites in the
framework catalyzes the chemical conversion of CO2 with propylene
oxide/4-cloromethyl-1,3-dioxolan-2-one/3-butoxy-1,2-epoxypropane
into cyclic carbonates in the high efficiency. This work represents a
very unique catalysis material containing the Brønsted acidic carboxyl
groups for the cycloaddition reaction of CO2 with epoxides.
Scheme 1. Cycloaddition of CO2 with Different Epoxides.
Table 2. Cycloaddition of CO2 and Epoxides under Various Reaction Conditions.a,b
Yield
Entry
1
Catalysts
Epoxides
Products
(%)
5.2
1a
Experimental Section
2
TBAB
10.8
Materials and General Methods. All materials for synthesis were purchased
commercially. Infrared spectra (IR) (400−4000 cm-1) were measured on a
Nicolet Avatar 360 FTIR spectrometer. Elemental analyses of C, H, and N were
performed with a Perkin-Elmer 2400C elemental analyzer. Thermogravimetric
analysis (TGA) was detected by a NETZSCH STA 449C thermal analyzer in a
N2 atmosphere (10 °C min-1). Powder X-ray diffraction (PXRD) data were
collected on a Bruker D8 ADVANCE X-ray powder diffractometer (Cu Kα,
1.5418 Å ). Gas sorption isotherms were tested with an ASAP 2020M adsorption
equipment.
3
4
5
1a/TBAB
1a/TBAB
1a/TBAB
9.0
>98.9
98.3
Catalytic Experiment. The catalytic experiments were executed at 80 °C and
2.0 MPa pressure in a 10 mL high pressure reactor, the reaction of epoxides with
CO2 was catalyzed by activated 1 and tetra-ntertbutylammonium bromide
(TBAB) cocatalyst under stirring for 4 h (100 rpm). 1H NMR analysis was
utilized to determine the products and yields.
6
1a/TBAB
83.1
90.9
Synthesis of [Ni(btzip)(H2btzip)]·2DMF·2H2O (1). The nickel wire (length of
3 cm, diameter of about 0.4 mm) was put into a bottle containing the mixture
of H2btzip (0.015 g, 0.05 mmol), acetonitrile (4 mL), DMF (4 mL), and two
drops of HCl (1.0 mol/L). The capped bottle was heated at 115 °C for 72 h, and
then cooled to room temperature, gaining blue sheet-like crystals in 52.0% yield
(based on H2btzip). Anal. Calcd. for C30H32NiN14O12: C, 42.93; H, 3.84; N,
23.36%. Found: C, 42.79; H, 3.72; N, 23.44%. IR (KBr, cm-1, Figure S1):
3131(w), 1663(vs), 1529(vs), 1387(s), 1134(s), 976(m), 653(m), 448(w).
Crystallography. The single crystal was measured on a Bruker SMART APEX
II CCD diffractometer with graphite monochromated MoKα radiation (λ =
0.71073 Å ). The structure was solved by direct methods and refined
anisotropically based on F2 by a full-matrix least-squares refinement with the
SHELXTL program.[63] Anisotropic thermal parameters were applied to non-
hydrogen atoms, and all hydrogen atoms of organic ligands were calculated and
added at the theoretical positions. The lattice molecules in complex cannot be
well refined, so the SQUEEZE routine of PLATON was utilized in refining.[34]
The crystallographic data and selected bond lengths/angles are provided in
Tables S1 and S2, respectively. CCDC 1567076 .
7
8
1a/TBAB
1a/TBAB
40.0
aMole amounts: epoxide (20 mmol), catalyst 1a (0.2 mmol), TBAB (2 mmol).
bReaction conditions: entry 3: 0.1 MPa, 25 °C, 48 h; entries 1-2 and 4-8: 2.0 MPa,
80 °C, 4 h.
Regarding the present catalytic results, we infer the following
mechanism.[26,27] First, the free –COOH Brønsted acid sites in channels
of 1a interacts with the epoxide O atoms, activating the epoxy ring.
Subsequently, the epoxy ring is opened because the Br− nucleophile
from TBAB attacks the less hindered C atom of epoxide. Through the
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
[29] H.-H. Wang, L. Hou, Y.-Z. Li, C.-Y. Jiang, Y.-Y. Wang, Z. Zhu, ACS
Appl. Mater. Interfaces. 2017, 9, 17969-17976.
Acknowledgements
[30] Z.-R. Jiang, H. Wang, Y. Hu, J. Lu, H.-L. Jiang, ChemSusChem. 2015,
8, 878-885.
We are grateful for financial support from the NSF of China (Grants
21471124, 21371142, and 21531007), and the Australian Research
Council Discovery project FT12010072.
[31] J. Liang, R.-P. Chen, X.-Y. Wang, T.-T. Liu, X.-S. Wang, Y.-B. Huang,
R. Cao, Chem. Sci. 2017, 8, 1570-1575.
[32] D. Feng, W.-C. Chung, Z. Wei, Z.-Y. Gu, H.-L. Jiang, Y.-P. Chen, D. J.
Darensbourg, H.-C. Zhou, J. Am. Chem. Soc. 2013, 135, 17105-17110.
[33] L.-J. Zhou, W.-H. Deng, Y.-L. Wang, G. Xu, S.-G. Yin, Q.-Y. Liu, Inorg.
Chem. 2016, 55, 6271-6277.
Keywords: metal-organic framework • crystal engineering •
crystal structure • CO2 capture and conversion• microporous
materials
[34] A. L. Spek, J. Appl. Crystallogr. 2003, 36, 7-13.
[35] V. A. Blatov, http://www.topos.ssu.samara.ru. 2007.
[36] P. Cui, Y.-G. Ma, H.-H. Li, B. Zhao, J.-R. Li, P. Cheng, P. B. Balbuena,
H.-C. Zhou, J. Am. Chem. Soc. 2012, 134, 18892-18895.
[37] N. H. Alsmail, M. Suyetin, Y. Yan, R. Cabot, C. P. Krap, L, J.; T. L.
Easun, E. Bichoutskaia, W. Lewis, A. J. Blake, M. Schrçder, Chem. Eur.
J. 2014, 20, 7317-7324.
[1]
[2]
A. Goeppert, M. Czaun, R. B. May, G. K. Surya Prakash, G. A. Olah, S.
R. Narayanan, J. Am. Chem. Soc. 2011, 133, 20164-20167.
K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald, E. D. Bloch, Z.
R. Herm, T. H. Bae, J. R. Long, Chem. Rev. 2012, 112, 724-781.
S. Chu, Science 2009, 325, 1599.
[3]
[4]
[5]
[38] Z. Liang, J. Du, L. Sun, J. Xu, Y. Mu, Y. Li, J. Yu, R. Xu, Inorg. Chem.
2013, 52, 10720-10722.
T. Sakakura, J. C. Choi, H. Yasuda, Chem. Rev. 2007, 107, 2365-2387.
Q. Liu, L. Wu, R. Jackstell, M. Beller, Nat. Commun. 2015, 6, 5933-
5948.
[39] Y. Yan, M. Jurícek, F. X. Coudert, N. A. Vermeulen, S. Grunder, A.
Dailly, W. Lewis, A. J. Blake, J. F. Stoddart, M. der, J. Am.
Chem. Soc. 2016, 138, 3371-3381.
[6]
[7]
[8]
[9]
X. Wang, Y. Zhou, Z. Guo, G. Chen, J. Li, Y. Shi, Y. Liu, J. Wang,
Chem. Sci. 2015, 6, 6916-6924.
J. Bayardon, J. Holz, B. Schffner, V. Andrushko, S. Verevkin, A. Preetz,
A. Brner, Angew. Chem. Int. Ed. 2007, 46, 5971-5974.
M. Aresta, A. Dibenedetto, A. Angelini, Chem. Rev. 2014, 114, 1709-
[40] N. Zhao, F. Sun, P. Li, X. Mu, G. Zhu, Inorg. Chem. 2017, 56, 6938-
6942.
[41] W. Fan, H. Lin, X. Yuan, F. Dai, Z. Xiao, L. Zhang, L. Luo, R. Wang,
Inorg. Chem. 2016, 55, 6420-6425.
1742
.
[42] Z. R. Herm, J. A. Swisher, B. Smit, R. Krishna, J. R. Long, J. Am. Chem.
Soc. 2011, 133, 5664-5667.
Y. He, W. Zhou, T. Yildirimbd, B. Chen, Energy Environ. Sci. 2013, 6,
2735-2744.
[10] Y. He, W. Zhou, G. Qian, B. Chen, Chem. Soc. Rev. 2014, 43, 5657-
5678.
[43] T. Li, D.-L. Chen, J. E. Sullivan, M. T. Kozlowski, J. K. Johnson, N. L.
Rosi, Chem. Sci. 2013, 4, 1746-1755.
[44] C. R. Wade, M. Din ă, Dalton Trans. 2012, 41, 7931-7938.
[45] H.-H. Wang, W.-J. Shi, L. Hou, G.-P. Li, Z. Zhu, Y.-Y. Wang, Chem. Eur.
J. 2015, 21, 16525-16531.
[11] S.-C. Xiang, Z. Zhang, C.-G. Zhao, K. Hong, X. Zhao, D.-R. Ding, M.-H.
Xie, C.-D. Wu, M. C. Das, R. Gill, K. M. Thomas, B. Chen, Nat.
Commun. 2011, 2, 204.
[46] P. Nugent, Y. Belmabkhout, S. D. Burd, A. J. Cairns, R. Luebke, K.
Forrest, T. Pham, S. Ma, B. Space, L. Wojtas, M. Eddaoudi, M. J.
Zaworotko, Nature 2013, 495, 80-84.
[12] H. Wu, Q. Gong, D. H. Olson, J. Li, Chem. Rev. 2012, 112, 836-868.
[13]
J.-R. Li, Y. Ma, M. C. McCarthy, J. Sculleya, J. Yu, H. K. Jeong, P. B.
Balbuena, H.-C. Zhou, Chem. Rev. 2011, 255, 1791-1823.
[47] J. An, N. L. Rosi, J. Am. Chem. Soc. 2010, 132, 5578-5579.
[48] H.-H. Wang, L.-N. Jia, L. Hou, W.-J. Shi, Z. Zhu, Y.-Y. Wang, Inorg.
Chem. 2015, 54, 1841-1846.
[14] Q. Yang, Q. Xu, H.-L. Jiang, Chem. Soc. Rev., 2017, 46, 4774-4808.
[15] L. Liu, S.-M. Wang, Z.-B. Han, M. Ding, D.-Q. Yuan, H.-L. Jiang, Inorg.
Chem. 2016, 55, 3558-3565.
[49] D. Farrusseng, C. Daniel, C. Gaudillère, U. Ravon, Y. Schuurman, C.
Mirodatos, D. Dubbeldam, H. Frost, R. Q. Snurr, Langmuir. 2009, 25,
7383-7388.
[16] W.-Y. Gao, C. Y. Tsai, L. Wojtas, T. Thiounn, C.-C. Lin, S. Ma, Inorg.
Chem. 2016, 55, 7291-7294.
[17] M. Ding, S. Chen, X,-Q. Liu, L.-B. Sun, J. Lu, H.-L. Jiang,
ChemSusChem 2017, 10, 1898-1903.
[50] Z. Zhao, Z. Li, Y.-S. Lin, Ind. Eng. Chem. Res. 2009, 48, 10015-10020.
[51] P. Chowdhury, C. Bikkina, S. Gumma, J. Phys. Chem. C 2009, 113,
6616-6621.
[18] L.-G. Ding, B.-J.Yao, W.-L. Jiang, J.-T. Li, Q.-J. Fu, Y.-A. Li, Z.-H. Liu,
J.-P. Ma, Y.-B. Dong, Inorg. Chem. 2017, 56, 2337-2344.
[19] T. Zhang, W. Lin, Chem. Soc. Rev. 2014, 43, 5982-5993.
[20] A. H. Chughtai, N. Ahmad, H. A. Younus, A. Laypkovc, F. Verpoort,
Chem. Soc. Rev. 2015, 44, 6804-6849.
[52] A. Masala, J. G. Vitillo, G. Mondino, C. A. Grande, R. Blom, M. Manzoli,
M. Marshall, S. Bordiga, ACS Appl. Mater. Interfaces 2017, 9, 455-463.
[53] Y. He, Z. Zhang, S. Xiang, F. R. Fronczek, R. Krishna, B. Chen, Chem.
Eur. J. 2012, 18, 613-619.
[21] W.-Z. Qiao, H. Xu, P. Cheng, B. Zhao, Cryst. Growth Des. 2017, 17,
3128-3133.
[54] H.-X. Zhang, H.-R. Fu, H.-Y. Li, J. Zhang, X. Bu, Chem. Eur. J. 2013, 19,
11527-11530.
[22] W. Jiang, J. Yang, Y.-Y. Liu, S.-Y. Song, J.-F. Ma, Chem. Eur. J. 2016,
22, 16991-16997.
[55] Z.-J. Guo, J. Yu, Y.-Z. Zhang, J. Zhang, Y. Chen, Y. Wu, L.-H. Xie, J.-R.
Li, Inorg. Chem. 2017, 56, 2188-2197.
[23] W.-Y. Gao, Y. Chen, Y. Niu, K. Williams, L. Cash, P. J. Perez, L.
Wojtas, J. Cai, Y.-S. Chen, S. Ma, Angew. Chem. Int. Ed. 2014, 53,
2615-2619.
[56] Y. He, W. Zhou, R. Krishnad, B. Chen, Chem. Commun. 2012, 48,
11813-11831.
[24] J. Song, Z. Zhang, S. Hu, T. Wu, T. Jiang, B. Han, Green Chem. 2009,
11, 1031-1036.
[57] H.-F. Ma, Q.-Y. Liu, Y.-L. Wang, S.-G. Yin, Inorg. Chem. 2017, 56, 2919-
2925.
[58] H. Fu, J. Zhang, Inorg. Chem. 2016, 55, 3928-3932.
[59] H. Xu, J. Cai, S. Xiang, Z. Zhang, C. Wu, X. Rao, Y.- Cui, Y. Yang, R.
Krishna, B.-L. Chen, G. Qian, J. Mater. Chem. A, 2013, 1, 9916-9921.
[60] J.-R. Li, R. J. Kuppler, H.-C. Zhou, Chem. Soc. Rev., 2009, 38, 1477-
1504.
[25] W.-Y. Gao, L. Wojtas, S. Ma, Chem. Commun. 2014, 50, 5316-5318.
[26] Z. Zhou, C. He, J. Xiu, L. Yang, C. Duan, J. Am. Chem. Soc. 2015, 137,
15066-15069.
[27] P.-Z. Li, X.-J. Wang, J. Liu, J.-S. Lim, R. Zou, Y. Zhao, J. Am. Chem.
Soc. 2016, 138, 2142-2145.
[61] M. Du, C.-P. Li, M. Chen, Z.-W. Ge, X. Wang, L. Wang, C.-S. Liu, J. Am.
Chem. Soc. 2014, 136, 10906-10909.
[28] A. C. Kathalikkattil, D. W. Kim, J. Tharun, H. G. Soek, R. Roshan, D. W.
Park, Green Chem. 2014, 16, 1607-1616.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
[62] Y. Ren, Y. Shi, J. Chen, S. Yang, C. Qi, H. Jiang, RSC Adv., 2013, 3,
2167-2170.
[63] G. M. Sheldrick, University of Göttingen: Göttingen, Germany, 1997.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704027
Chemistry - A European Journal
FULL PAPER
FULL PAPER
Through employing a triazolyl-carboxyl
linker, a stable porous Ni-MOF was
constructed, which contains free carboxyl
groups in channels and reveals not only
high CO2 and C2H6 loadings but also
significantly selective capture for CO2 and
C2H6 over CH4 and CO, as well as highly
efficient catalytic activity in the
cycloaddition reaction of CO2 with
epoxides. The multi-point framework-
CO2/C2H6 interactions were confirmed by
GCMC simulations.
Yong-Zhi Li, Hai-Hua Wang, Hong-Yun
Yang, Lei Hou*, Yao-Yu Wang,
Zhonghua Zhu
Page 1 – Page 7
An Uncommon Carboxyl-Decorated
MOF with Selective Gas Adsorption and
Catalytic Conversion of CO2
This article is protected by copyright. All rights reserved.