An N-rich metal-organic framework with an rht topology: High CO2 and C2 hydrocarbons uptake and selective capture from CH4

Article abstract of DOI:10.1039/c4cc00375f

We report the storage capacities and separation selectivity of an rht-type s-heptazine-based metal organic framework (MOF), [Cu₃(TDPAH)(H ₂O)₃]·13H₂O·8DMA, 1, (where TDPAH is 2,5,8-tris(3,5-dicarboxylphenylamino

Full text of DOI:10.1039/c4cc00375f

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An N-rich metal–organic framework with an rht
topology: high CO and C hydrocarbons uptake
and selective capture from CH4†
2
2
Cite this: Chem. Commun., 2014,
0, 5031
5
Received 16th January 2014,
Accepted 21st March 2014
a
a
a
a
a
a
a
Kang Liu, Baiyan Li, Yi Li, Xu Li, Fen Yang, Guang Zeng, Yu Peng,
b
a
a
a
c
Zhijuan Zhang, Guanghua Li, Zhan Shi,* Shouhua Feng and Datong Song
DOI: 10.1039/c4cc00375f
www.rsc.org/chemcomm
We report the storage capacities and separation selectivity of an starting material in industrial processes that convert methane into C2
rht-type s-heptazine-based metal organic framework (MOF), hydrocarbons, such as ethane and acetylene.
[
Cu
3,5-dicarboxylphenylamino)-s-heptazine and DMA is N,N-dimethyl- attention in recent years and have found use in gas storage and
acetamide) for C hydrocarbons and CO over CH . MOF 1 displays separation, because of their large surface area, tunable pore size and
the highest C /CH selectivity of 80.9 as well as record high C shape, as well as adjustable host–guest interactions. In order to
and C adsorption enthalpies. Theoretical calculations reveal that achieve high gas uptake, the rht-type MOFs built on supramolecular
s-heptazine and NH groups within the framework have synergistic building blocks (SBBs) serve as an excellent platform. To our knowl-
3
(TDPAH)(H
2
O)
3
]Á13H
2
OÁ8DMA, 1, (where TDPAH is 2,5,8-tris-
Microporous metal–organic frameworks (MOFs) have drawn great
3
(
2
2
4
2
H
2
4
2 4
H
2 6
H
effects on CO
2
binding.
edge, the first (3,24)-connected rht-type MOF was reported by
Eddaoudi and co-workers. Thereafter, some remarkable results have
4
Methane, the major component of natural gas, is not only a prevalent been reported (see Fig. S1 and Table S1 in the ESI†). In this family of
and inexpensive fuel for industry and residential use but also a useful rht-type MOFs, each dendritic hexacarboxylate ligand with 3-fold
C
1
feedstock in chemical and petrochemical industries for the symmetry is linked by 24 ‘‘square paddlewheel’’ M
2 4
(COO) units to
production of various C and C chemicals, such as chloromethanes form a robust network that possesses both a high concentration of
1
2
1
and acetylene. For chemical and petrochemical applications, impu- open metal sites (OMSs) and a highly porous structure with a large
rities in methane as a starting material may complicate the product surface area and pore volume. By adjusting the pore dimensions and
isolation processes. Moreover, certain impurities may inhibit the functionalizing the interior surface, the gas separation selectivity can
conversion of methane. For example, carbon dioxide poisons the be enhanced. Although some progress has been made on porous
2
5
6
Li/MgO catalyst that converts methane into ethane and ethylene.
Natural gas contains 80–95% of methane, which requires further separation of C
purification prior to various chemical processes. The major impurities perature, MOFs that excel in both tasks are scarce.
in naturally occurring methane are C hydrocarbons. In addition, Previously, Eddaoudi’s group and our group incorporated a
carbon dioxide is also present in natural gas in various amounts. It is, 1,3,5-triazine functional group in the ligand structure design
MOFs for either the adsorption of C hydrocarbons and CO or the
2
2
7
4
,8
2
hydrocarbons and CO
2
over CH
at room tem-
2
9
2
therefore, critical to remove carbon dioxide and C hydrocarbons for MOF synthesis. The resulting rht-type MOF rht-MOF-7 /
from methane. Materials that can preferentially adsorb carbon Cu-TDPAT (where TDPAT = 2,4,6-tris(3,5-dicarboxylphenyl-
1
0
dioxide and C hydrocarbons over methane are highly desirable. amino)-1,3,5-triazine) exhibited a balance between large storage
2
Such porous materials can also be used to extract products from the capacity and high selectivity for CO . To tune the CO affinity,
2
2
we modified our ligand by replacing the 1,3,5-triazine group
with an s-heptazine group that has higher density of Lewis
basic sites (LBSs). Interestingly, the resulting MOF displays
a
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry,
College of Chemistry, Jilin University, Changchun 130012, P. R. China.
E-mail: zshi@mail.jlu.edu.cn
excellent adsorption selectivity for C
2 2
hydrocarbons and CO
over methane. The preliminary results are reported herein.
b
c
Institute of Atmospheric Environment Safety and Pollution Control,
Jinan University, Jinan 510632, P. R. China
Crystals of [Cu (TDPAH)(H O) ]Á13H OÁ8DMA, 1, can be prepared
3
2
3
2
from 2,5,8-tris(3,5-dicarboxylphenylamino)-s-heptazine acid (H TDPAH)
6
Davenport Chemical Research Laboratories, Department of Chemistry,
University of Toronto, 80 St. George Street, Toronto, Ontario, Canada
Electronic supplementary information (ESI) available: Experimental details and
and Cu(NO ) under solvothermal conditions in good yield. Single-
3
2
crystal X-ray diffraction analysis reveals that the three isophthalate
moieties in TDPAH are linked through copper paddlewheel units to
form cuboctahedral supramolecular building blocks, which are
†
characterization data, as well as CIF files. CCDC 928821. For ESI and crystal-
lographic data in CIF or other electronic format see DOI: 10.1039/c4cc00375f
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Fig. 1 Structure of 1. A portion of the (3,24)-connected rht-net built on
TDPAH is shown (Cu, green; C, gray; O, red; N, blue. H atoms are omitted
for clarity).
covalently bonded through the isophthalate moieties to yield a (3,24)-
connected rht-type network of 1 (Fig. 1). Similar to other reported (3,24)-
connected structures, such as PCN-61, NU-100, NOTT-112 and
Cu-TPBTM, there are three types of cages, namely, cuboctahedron
(
cub-O ), truncated tetrahedron (T-T ), and truncated octahedron
h
d
(
T-O
h
) in 1 in a 1 : 2 : 1 ratio (see Fig. S4 in the ESI†). The diameters
Fig. 2 (a) CO
desorption: open). (b) C
2
, CH
4
and N
2
sorption isotherms at 298 K (adsorption: filled;
of spheres representing the void inside these polyhedra are 1.2, 1.04
2 2 2 4 2 6 4
H , C H , C H and CH sorption isotherms at
and 1.72 nm, respectively. The total accessible volume after the removal 298 K. (adsorption: filled; desorption: open).
of the guest and coordinated solvent molecules is 71.7% using the
11
PLATON/VOID routine, and the calculated density of the desolvated
À3
À1
framework is 0.775 g cm
.
reach 17.1 mmol g . Its volumetric capacity is 297 v/v. Detailed
The activated samples were prepared by exchanging the solvent in information is provided in the ESI† (Fig. S40).
the as-synthesized 1 with CH OH, followed by evacuation under high The C2 hydrocarbons (C H , C H and C H ) and C (CH4)
3
2
2
2
4
2
6
1
vacuum at 100 1C for 10 h. A comparison of PXRD patterns of hydrocarbon low-pressure adsorption–desorption isotherms of 1 were
as-synthesized, activated 1 and 1 after adsorption of CO was made measured at 273 and 298 K (0–1 atm). The uptake capacities at 1 atm
carefully. The water/moisture stability was tested in boiling water and 273 K for C , C , C , and CH are 202.2, 163.9, 162.9, and
1 day) and in air (30 days). The framework remained intact as clearly 32.7 cm g , respectively, while those at 1 atm and 298 K are 155.7,
2
2
H
2
2
H
4
2
H
6
4
3
À1
(
3
À1
indicated by the PXRD patterns of the samples recorded after these 116.7, 107.2, and 22.4 cm g , respectively. (see Fig. 2b, Fig. S16, S19,
tests (see Fig. S6 and S7 in the ESI†). Permanent porosity of activated S22 and S25 in the ESI†). The uptake capacity of 1 for C at 298 K is
was confirmed by N adsorption–desorption isotherms at 77 K among the highest for MOF materials (e.g. HKUST (201 cm g ),
2 2
H
3
À1
1
2
3
À1
3
À1
which showed a reversible type-I isotherm (see Fig. S9 and S10 in CoMOF-74 (197 cm
g
), NOTT-101 (184 cm
g ), PCN-16
3
À1
3
À1
3
À1
the ESI†). The Langmuir and BET surface areas are 2540 and (176 cm g ), Cu
2
(ebtc) (160 cm g ) and UTSA-20 (150 cm g )).
171 m g , respectively. The total pore volume calculated from The separation ratios of C hydrocarbons (C , C and C
) are based on Henry’s law selectivity. The calculated
/CH and C /CH adsorption selectivities at 273 K
low-pressure adsorption–desorption isotherms of 1 were are 102.3 : 1, 75.4 : 1, and 27.1 : 1, respectively, while those at 298 K are
measured at 273, 288, and 298 K (0–1 atm). At 298 K, the uptake 80.9, 40.6 : 1, and 12.5 : 1, respectively (some virial parameters are
2
À1
2
2
2
H
2
2
H
4
2 6
H )
3
À1
the N
the value calculated from single-crystal data which is 0.89 cm g
The CO
2
isotherms is 0.91 cm g , which is in good agreement with versus C
1
(CH
, C
4
3
À1
.
C
2
H
2
/CH
4
2
H
4
4
2
H
6
4
2
3
À1
amounts are 116 cm g (STP = standard temperature and pressure; summarized in Table S6, ESI†). To the best of our knowledge, the
2
0
3
À1
2.8 wt%, 90 v/v) and 20.2 cm g (STP; 4.0 wt%, 16 v/v) at 1.0 and C H /CH separation selectivity of 80.9 is the highest to date (see
2 2 4
3
À1
.1 atm, respectively. At 273 K, they are 192 cm g (STP; 37.7 wt%, Table S5 in the ESI†).
3
À1
1
49 v/v) and 50.6 cm g (STP; 9.9 wt%, 39 v/v) at 1.0 and 0.1 atm,
respectively (see Fig. 2a and Fig. S13 in the ESI†). These values are
substantially higher than those obtained for most of the previously well-established and reliable methodology fitting from their adsorp-
reported rht-type structures (Table S3 in ESI†), and among the highest tion isotherms at 273 and 298 K (273, 288, and 298 K for CO ). The
The isosteric heats (Qst) of 1 for the five gases (CO
C H , and C H ) were calculated using the virial method, which is a
2
, CH
4
, C
2 2
H ,
12
2 4 2 6
2
À1
for MOFs reported to date with both OMSs and LBSs (Table S4 in low coverage Qst value of CO
2
adsorption in 1 (33.8 kJ mol ) is the
ESI†). To the best of our knowledge, the LBS density is the highest second highest one among values of the reported rht-MOFs, while Cu-
À3
À1
(
5.4 nm ) in rht-MOFs. Compared with CO , N and CH were TDPAT exhibits the highest value (42.2 kJ mol ) so far. The isosteric
2 2 4
À1
hardly adsorbed at 273 K and 298 K. From these data, the calculated heats at zero coverage are 33.0, 45.0, 23.5 and 13.8 kJ mol for C
CO /N and CO /CH adsorption selectivities based on Henry’s law , C and CH , respectively. It is worth noting that compound 1
2 6
selectivity are 69.3 : 1 and 20.3 : 1 at 273 K and 36.7 : 1 and 10.0 : 1 at shows the highest adsorption enthalpy of C H (33.0 kJ mol ) and
2 6
H ,
2
2
2
4
C
2
H
4
2
H
2
4
À1
À1
2
98 K, respectively. At 298 K and 48 bar, the excess CO
2
uptakes of 1
C
2
H
4
(45 kJ mol ) at zero loading for MOFs under the same
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Fig. 4 Preferential CO
2
adsorption sites and the corresponding binding
energies obtained from first-principles calculations.
have synergistic effects on CO binding. The selective adsorp-
2
tion properties of 1 make it a promising candidate for methane
purification and recycling. Future efforts in our laboratory will
focus on the frameworks with an imino s-heptazine backbone
2
Fig. 3 Density distribution of the center-of-mass of CO molecules along
the c-axis in the unit cell of 1 at 273 K and 1 bar simulated by GCMC.
to further improve the C
2 2
and CO storage capacity and
13
conditions. The adsorption enthalpies for CO
are all greater than that for CH , presumably because of the group reporting similar results during the proof stage.
combined effects of the van der Waals host–guest interactions and This work was financially supported by the Foundation of the
2 2 2 2 4
, C H , C H and selectivity. We found a newly published study by Eddaoudi
1
6
C
2
H
6
4
the electrostatic host–guest interactions in this system, thus leading National Natural Science Foundation of China (No. 21371069).
to high selectivity for C2 hydrocarbons and CO2 over CH . (see
Fig. S13–S27 in the ESI†).
4
Notes and references
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1
2
3
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4
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level, GCMC and first-principles calculations were carried out.
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obtained from GCMC simulations reveals that CO molecules
in 1 prefer to locate at both the open Cu metal sites and NH
groups within the framework (see Fig. 3 and Fig. S43 in the
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2
we calculated the binding energies of CO at NH sites using the
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4
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À1
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1
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1
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H
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2 6
H
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Chem. Commun., 2014, 50, 5031--5033 | 5033