Abstract
Four Zn metal–organic frameworks (MOFs), {[Zn2(2,6-ndc)2(2-Pn)]·DMF}n (1), {[Zn2(cca)2(2-Pn)]·DMF}n (2), {[Zn2(thdc)2(2-Pn)]·3DMF}n (3), and {[Zn2(1,4-ndc)2(2-Pn)]·1.5DMF}n (4), were synthesized from zinc nitrate and N,N′-bis(pyridin-2-yl)benzene-1,4-diamine (2-Pn) with naphthalene-2,6-dicarboxylic acid (2,6-H2ndc), 4-carboxycinnamic acid (H2cca), 2,5-thiophenedicarboxylic acid (H2thdc), and naphthalene-1,4-dicarboxylic acid (1,4-H2ndc), respectively. MOFs 1–4 were all constructed from similar dinuclear paddlewheel {Zn2(COO)4} clusters and resulted in the formation of three kinds of uninodal 6-connected non-interpenetrated frameworks. MOFs 1 and 2 suit a topologic 48·67-net with 17.6% and 16.8% extra-framework voids, respectively, 3 adopts a pillared-layer open framework of 48·66·8-topology with sufficient free voids of 39.9%, and 4 features a pcu-type pillared-layer framework of 412·63-topology with sufficient free voids of 30.9%. CO2 sorption studies exhibited typical reversible type I isotherms with CO2 uptakes of 55.1, 84.6, and 64.3 cm3 g−1 at 195 K and P/P0 =1 for the activated materials 1′, 2′, and 4′, respectively. The coverage-dependent isosteric heat of CO2 adsorption (Qst) gave commonly decreased Qst traces with increasing CO2 uptake for all the three materials and showed an adsorption enthalpy of 32.5 kJ mol−1 for 1′, 38.3 kJ mol−1 for 2′, and 23.5 kJ mol−1 for 4′ at zero coverage.
Highlights
Metal–organic frameworks (MOFs) are infinite arrays of metal ions connected by organic modules through coordination bonds [1]
Such materials possess fascinating structure variations and some can sustain considerable porosity and internal surface area, which is associated with intrinsic photo and magnetic properties. These properties have led to the evaluation of MOFs for various practical applications in gas adsorption/separation [2,3,4,5], ion exchange [6,7], sensing [8,9], catalysis [10], magnetism [11], drug delivery [12], etc
Crystalline MOF materials are usually constructed by metal clusters regarded as secondary building units (SBUs) and organic ligands [13]
Summary
Metal–organic frameworks (MOFs) are infinite arrays of metal ions connected by organic modules through coordination bonds [1] Such materials possess fascinating structure variations and some can sustain considerable porosity and internal surface area, which is associated with intrinsic photo and magnetic properties. These properties have led to the evaluation of MOFs for various practical applications in gas adsorption/separation [2,3,4,5], ion exchange [6,7], sensing [8,9], catalysis [10], magnetism [11], drug delivery [12], etc.
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