Storage and sorption properties of acetylene in jungle-gym-like open frameworks

The acetylene-sorption properties of six porous coordination polymers (PCPs), [M₂(L)₂(dabco)]_n (dabco=1,4- diazabicyclo[2.2.2]octane, M=Cu²⁺ (1), Zn²⁺ (2), L=1,4-benzenedicarboxylate (bdc; 1a, 2a), 1,4-naphthalenedicarboxylate (ndc; 1b, 2b), 9,10-anthracenedicarboxylate (adc; 1c, 2c)), were investigated. The acetylene sorption isotherms of 1 and 2 measured at 195 K are of type I and show a steep increase at low relative pressures. The sorption properties of carbon dioxide at 195 K were also investigated. Compounds 1 and 2 showed a large difference in onset pressure between acetylene sorption isotherms, although the difference between the carbon dioxide sorption isotherms is not so significant. In particular, 2c displayed a remarkable affinity for acetylene. The acetylene sorption isotherm at 298 K showed that the adsorption amounts for 2c and 2b at 298 K, 1 atm (101 and 106 mLg^-1, respectively) were higher than those of other conventional porous materials. Notably, of the compounds 1 and 2, the porous crystals 2c had the highest affinity for acetylene.