Efficient adsorption separation of methane from CO2 and C2-C3 hydrocarbons in a microporous closo-dodecaborate [B12H12](2-) pillared metal-organic framework

A closo-dodecaborate [B12H12](2-) functionalized metal organic framework (MOF), BSF-3, constructed by the selfassembly of the Cu(II) cation, 1,4-di(pyridin-4-yl)benzene linker and cluster [B12H12](2)(-) pillar was investigated for the adsorption separation of light hydrocarbons. The activated MOF exhibited efficient uptake of CO2 and C2-C3 hydrocarbons with high separation selectivity of C3H8 (138), C2H2 (205), C2H4 (23), C2H6 (13) and CO2 (9) over CH4, outperforming many popular MOFs. The practical gas separation ability for C2H2/CH4, CO2/CH4 and C3H8/C2H6/CH4 was confirmed by mixed gas breakthrough experiments with no capacity loss after 7 cycles, indicating its potential for purification of methane from natural gas and pyrolysis gas. The gas bonding sites within the framework were further studied by modelling studies, which indicated that the anionic [B12H12]2pillar contributed the most to capturing hydrocarbon molecules by multiple B-Hd-center dot center dot center dot Hd+-C interactions.