Highly Enhanced Gas Uptake and Selectivity via Incorporating Methoxy Groups into a Microporous Metal–Organic Framework

A porous metal–organic framework [Cu 2 L(H 2 O) 2 ]·7DMF·4H 2 O ( UTSA-90, H 4 L = 2′,5′-dimethoxy-[1,1′:4′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid) functionalized with methoxy groups has been successfully constructed and structurally characterized, which is isoreticular to NOTT-101 . A single crystal structure determination reveals that the incorporation of bulky methoxy groups can efficiently split the large pores and channels of NOTT-101a into smaller ones within UTSA-90 . Compared with NOTT-101a, the activated UTSA-90a exhibits the significantly enhanced C 2 H 2 (214 vs 184 cm 3 g –1 ) and CO 2 (125 vs 83 cm 3 g –1 ) adsorption capacities at 295 K and 1 bar. It is worth noting that the CO 2 uptake of UTSA-90a represents the highest reported for all the NbO-type metal-organic frameworks (MOFs). In addition, UTSA-90a also shows a significant enhancement in adsorptive selectivities for the separation of C 2 H 2 /CH 4, CO 2 /CH 4, and CO 2 /N 2 mixtures at ambient conditions. This work indicates that introducing bulky functional groups on the linker might be a promising approach to tune pore sizes and environments in MOFs for enhancing their gas adsorption and separation properties.