Significantly Enhanced CO2/CH4 Separation Selectivity within a 3D Prototype Metal-Organic Framework Functionalized with OH Groups on Pore Surfaces at Room Temperature

A new three-dimensional microporous metal-organic framework (MOF) Zn(BDC-OH)(DABCO)(0.5)center dot(DMF)(2)(H2O) (UTSA-25; H2BDC-OH = 2-hydroxybenzenedicarboxylic acid, DABCO = 1,4-diazabicyclo[2.2.2]octane) with functional -OH groups on the pore surfaces was solvothermally synthesized and structurally characterized. UTSA-25 features a three-dimensional structure with 3D intercrossed channels of about 7.5 x 7.5, 3.2 x 4.7, and 3.2 x 4.7 angstrom(2), respectively. The small pores and the functional -OH groups on the pore surfaces within the activated UTSA-25a have enabled their strong interactions with CO2 of adsorption enthalpy of 22.5 kJmol(-1), which is higher than that of 17.5 kJmol(-1) in the original MOF Zn(BDC)(DABCO)(0.5) without the function-alized -OH groups. Accordingly, CO2/CH4 separation selectivities in UTSA-25a of 17.2 and 12.5 at 273 and 296 K, respectively, are much higher than those of 4.4 and 3.7 in Zn(BDC)(DABCO)(0.5), thus highlighting UTSA-25a as a very promising porous material for industrially important CO2/CH4 separation.