Optimized nanospace of coordination isomers with selenium sites for acetylene separation

The safe storage and separation of acetylene (C2H2) is difficult and essential, due to its explosive properties and wide usage for various industrial products. With a generally low energy cost, highly efficient adsorption separation has been considered as a promising solution. Taking advantage of the inbuilt nature of a tunable pore space, a porous coordination polymer (NTU-56) was prepared from a selenium-containing carboxylate ligand and Cu2+ ions. Triggered by water at different temperatures, NTU-56 transformed into two other porous frameworks (NTU-57 and NTU-58) with different topologies and pore environments. Single-component gas adsorption experiments showed that this new group of porous isomers featured systematically varied adsorption selectivity for C2H2/CO2, two gases that have extremely similar molecular sizes and boiling points. More interestingly, among the isomers, NTU-58, a rare 2D, flexible, and water-stable framework, has the highest C2H2 uptake (60 cm3 g-1) and C2H2/CO2 selectivity (13.9, 1/1, v/v, 1 bar) at 273 K, derived from the synergetic effect of the unique pore sizes (4.5 and 5.5 Å) and pore surface polarity, where the Cu2+ and selenium sites are exposed for preferred C2H2 interactions. Efficient and recyclable C2H2/CO2 separation was also confirmed via breakthrough experiments, even with wet feed-gas.