Communications
DOI: 10.1002/anie.201102329
Microporous MOFs
A Microporous Copper Metal–Organic Framework with High H2 and
CO2 Adsorption Capacity at Ambient Pressure**
Daniel Lꢀssig, Jçrg Lincke, Jens Moellmer, Christian Reichenbach, Andreas Moeller,
Roger Glꢀser, Grit Kalies, Katie A. Cychosz, Matthias Thommes, Reiner Staudt, and
Harald Krautscheid*
Metal–organic frameworks (MOFs) as highly porous materi-
als have gained increasing interest because of their distinct
adsorption properties.[1–3] They exhibit a high potential for
applications in gas separation and storage,[4] as sensors[5] as
well as in heterogeneous catalysis.[6] In the last few years, the
H2 storage capacity of MOFs has been considerably
increased. Mesoporous MOFs show high adsorption capaci-
ties for CH4, CO2, and H2 at high pressures.[2,3,7–10] To increase
the uptake of H2 and CO2 by physisorption at ambient
pressure, adsorbents with small micropores as well as high
specific surface areas and micropore volumes are
required.[11,12] Such microporous materials seem to be more
appropriate for gas-mixture separation by physisorption than
mesoporous materials. For gas separation in MOFs the
interactions between the fluid adsorptive and “open metal
sites” (coordinatively unsaturated binding sites) or the ligands
are regarded as important.[13] Industrial processes, such as
natural-gas purification or biogas upgrading, can be improved
with those materials during a vapor-pressure swing adsorption
cycle (VPSA cycle) or a temperature swing adsorption cycle
(TSA cycle).[14] The microporous MOF series CPO-27-M
(M = Mg, Co, Ni, Zn), for example, shows very high CO2
uptakes at low pressures (< 0.1 MPa).[15,16] Concerning H2
adsorption, the microporous MOF PCN-12 offers with
3.05 wt% the highest uptake at ambient pressure and 77 K
reported to date.[17]
Herein, we present a novel microporous copper-based
MOF 13[Cu(Me-4py-trz-ia)] (1; Me-4py-trz-ia2ꢀ = 5-(3-
methyl-5-(pyridin-4-yl)-4H-1,2,4-triazol-4-yl)isophthalate)
with extraordinarily high CO2 and H2 uptakes at ambient
pressure, the H2 uptake being similar to that in PCN-12. The
ligand Me-4py-trz-ia2ꢀ (Figure 1a), which can be obtained
from cheap starting materials by a three-step synthesis in
good yield, combines carboxylate, triazole, and pyridine
functions and is adopted from a recently presented series of
linkers,[18] for which up to now only a few coordination
polymers are known.[19–22]
[*] D. Lꢀssig, J. Lincke, Prof. Dr. R. Glꢀser, Prof. Dr. H. Krautscheid
Universitꢀt Leipzig, Fak. fꢁr Chemie und Mineralogie
Johannisallee 29, 04103 Leipzig (Germany)
Single crystals of 1 that are suitable for X-ray crystal
structure analysis were prepared by diffusion of copper
sulfate and H2(Me-4py-trz-ia). Larger quantities of micro-
crystalline 1 are obtained not only by solvothermal synthesis,
but also in multigram scale by simple reflux of the starting
materials in water/acetonitrile (see Supporting Information).
According to the single crystal X-ray structure analysis, 1
crystallizes in the monoclinic space group P21/c (no. 14) with
four formula units per unit cell. The asymmetric unit contains
one linker anion and two crystallographically independent
Cu2+ ions residing on inversion centers. The copper ion Cu1 is
coordinated in a square-planar fashion by two monodentate
carboxylate and two pyridine functions in trans position
leaving two accessible open metal sites per Cu1 atom
(Figure 1b), whereas the second copper ion Cu2 is coordi-
nated by monodentate triazole and chelating carboxylate
groups forming a distorted octahedron (Figure 1c). For this
reason, both copper ions represent planar fourfold nodal
points and the ligands act as tetradentate linkers in a 3D
network with pts topology[23] and a 3D pore system (Fig-
ure 1d). With narrow channels of about 250 ꢀ 600 pm in
crystallographic c direction connecting the micropores with a
diameter of approximately 550 pm, the structure has a
calculated porosity of about 55% according to PLATON.[24]
Powder X-ray diffraction (PXRD) studies on the as-
synthesized microcrystalline sample 1a confirm both, the
agreement with the simulated powder pattern of 1 based on
E-mail: krautscheid@rz.uni-leipzig.de
J. Moellmer, Dr. A. Moeller
Institut fꢁr Nichtklassische Chemie e.V.
Permoserstrasse 15, 04318 Leipzig (Germany)
C. Reichenbach, Dr. G. Kalies
Universitꢀt Leipzig, Fak. fꢁr Physik u. Geowissenschaften
Linnꢂstrasse 5, 04103 Leipzig (Germany)
Dr. K. A. Cychosz, Dr. M. Thommes
Quantachrome Instruments
1900 Corporate Drive, Boynton Beach, FL 33426 (USA)
Prof. Dr. R. Staudt
Hochschule Offenburg
Fak. fꢁr Maschinenbau und Verfahrenstechnik
Badstrasse 24, 77652 Offenburg (Germany)
[**] We gratefully acknowledge financial support by Deutsche For-
schungsgemeinschaft (DFG SPP 1362-Porçse metallorganische
Gerꢁstverbindungen, STA 428/17-1, KR 1675/7-1, GL 290/6-1; and
KA 1560/3-2, 4-2), the University of Leipzig (PbF-1) and the
graduate school BuildMoNa is gratefully acknowledged. D.L. thanks
the Fonds der Chemischen Industrie for a fellowship, J.L. acknowl-
edges the ESF fellowship. We thank F. Kettner for DTA/TG-MS
analyses, Riaz Ahmad and Dr. Charlie Thibault (Quantachrome
Instruments, US) for help with the N2 (77 K), Ar (87 K) and H2 (77,
87 and 97 K) sorption experiments on sample 1d, and Dr. Angela
Puls (Rubotherm GmbH, Bochum (Germany)) for measuring the N2
(77 K) adsorption isotherms on sample 1a.
Supporting information for this article is available on the WWW
10344
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2011, 50, 10344 –10348