Two Cu(II) microporous frameworks based on a bifunctional linker and selective gas adsorption properties for CO2

Abstract

Two microporous metal-organic frameworks assembled of Cu(II) ions and bifunctional imidazoly/carboxylate containing organic compound (4-(1H-imidazole-4-yl) benzoate), namely [Cu2(L)4]·DMA·3H2O (1) and [Cu(L)2]·2H2O (2), are structurally characterized. Compound 1 shows 3-fold interpenetrating binodal 4-connected CdSO4 microporous architecture with Point (Schläfli) symbol of (65·8), while complex 2 is a supramolecular framework by stacking in an ···AAA··· configuration from two-dimensional 44 layers with one-dimensional open channels with 11.99 ​× ​11.99 ​Å2. MOF 1 shows selective adsorption capacity for CO2 (32.24 ​cm3/g) over N2 and CH4, while 2 has the uptake of 45.67 ​cm3/g for CO2 and 23.81 ​cm3/g for CH4. The corresponding the heat of adsorption calculated by Clausius–Clapeyron equation are 28.5 and 32.3 ​kJ ​mol−1. The adsorption capacity of CO2 is comparative higher than CH4 and N2, ascribing to the electrostatic interactions between CO2 and narrow pores decorated with uncoordinated imidazoly-N atoms.