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 · (DMF) 2 (H 2 O) (UTSA‐25; H 2 BDC‐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 × 7.5, 3.2 × 4.7, and 3.2 × 4.7 Å 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 CO 2 of adsorption enthalpy of 22.5 kJ mol –1 , which is higher than that of 17.5 kJ mol –1 in the original MOF Zn(BDC)(DABCO) 0.5 without the functionalized –OH groups. Accordingly, CO 2 /CH 4 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 CO 2 /CH 4 separation.