Molecular sieving effect ofnonporous 3-D MOF induced by selective removal of a ligated olvent molecule

Abstract

A nonporous 3-D framework structure showing gas selectivity through sieving effect was produced from Ni2+ and trimesic acid (BTC). The nonporous 3-D framework doesn’t show any apparent porosity since the 1-D solvent channel along the a-axis is filled with a dimethyl ammonium ion as a counter cation. Among two different DMF molecules and a MeOH molecule ligated to the two metals out of three in the metal cluster in the 3-D framework, the MeOH molecule can be selectively removed from the framework by vacuum-drying the framework at 373 K while keeping the two coordinated DMF molecules intact. The selective removal of the ligated MeOH molecule leads to the generation of 1-D channel along the b-axis for selective gas sorption. The framework shows adsorption of CO2 with small kinetic diameter but does not show any adsorption of N2 and CH4 with large kinetic diameters. In addition, adsorption experiment for C2Hn (n = 2, 4, 6) gases indicates that adsorption amounts of the gases depend on the kinetic diameters of the C2Hn molecules.