Direct Evidence: Enhanced C2H6 and C2H4 Adsorption and Separation Performances by Introducing Open Nitrogen-Donor Sites in a MOF

To comparably analyze the influence of a porous environment on the gas adsorption in MOFs, based on an imidazole-decorated MOF, {[Zn(imtp)]·DMA·1.5H2O}n (1-im, H2imtp = 2-(imidazol-1-yl) terephthalic acid), an analogue MOF, {[Zn(tztp)]·DMA}n (1-tz, H2tztp = 2-(1H-1,2,4-triazol-1-yl) terephthalic acid) has been synthesized by replacing imidazole with triazole motifs. The two MOFs are isostructural frameworks containing 1D channels; however, they possess different porous wall environments. The open nitrogen-decorated channels in 1-tz lead to significantly enhanced C2H6 (76.5 cm3 g–1) and C2H4 (73.1 cm3 g–1) uptakes at 298 K and 1 atm, which are 5 times of the adsorption amounts of C2H6 and C2H4 in 1-im that is the absence of exposed N atoms in the channels. Furthermore, the activated 1-tz also reveals higher adsorption selectivities for C2H6 and C2H4 over CH4. The different sorption properties were further uncovered by theoretical simulations.