A coordination network featuring two distinct copper(II) coordination environments for highly selective acetylene adsorption

Single crystals of 2D coordination network {Cu2L2 ⋅ (DMF)3(H2O)3}n (1-DMF) were prepared by reaction of commercial reagents 3-formyl-4-hydroxybenzoic acid (H2L) and Cu(NO3)2 in dimethylformamide (DMF). The single-crystal structure shows two distinct Cu(II) coordination environments arising from the separate coordination of Cu(II) cations to the carboxylate and salicylaldehydato moieties on the linker, with 1D channels running through the structure. Flexibility is exhibited on solvent exchange with ethanol and tetrahydrofuran, while porosity and the unique overall connectivity of the structure are retained. The activated material exhibits type I gas sorption behaviour and a BET surface area of 950 m2 g−1 (N2, 77 K). Notably, the framework adsorbs negligible quantities of CH4 compared with CO2 and the C2Hn hydrocarbons. It exhibits exceptional selectivity for C2H2/CH4 and C2H2/C2Hn, which has applicability in separation technologies for the isolation of C2H2