Electrostatic force-driven lattice water bridging to stabilize a partially charged indium MOF for efficient separation of C2H2/CO2 mixtures?

Journal of Materials Chemistry A Pub Date: 2022-04-05 DOI: 10.1039/D1TA10569H

Abstract

Highly stable metal–organic frameworks (MOFs) with accessible sites have gradually been valued because of their excellent performance. Here, we proposed a steric hindrance effect to construct a partially charged MOF with electrostatic forces for efficient C2H2/CO2 separation. Two MOFs, [Me2NH2]·[In(BDTA)] 5.5DMF·4H2O (FJU-117, BDTA is [4,4′,4′′,4′′′-([1,1′-biphenyl]-4,4′-diylbis(azanetriyl)) tetrabenzoic acid]) and [In(4Me-BDTA)·0.5H2O]·6DMF·2H2O (FJU-118) were synthesized using a similar procedure except that BDTA in FJU-117 was replaced with 4Me-BDTA in FJU-118. The four methyl groups in 4Me-BDTA in FJU-118 obviously restrict the rotation of the two C–N bonds of ligands. The steric hindrance effect of the 4Me-BDTA results in 7-coordinated In3+ ions in FJU-118, compared to 8-coordinated ones in FJU-117. Accessible sites in FJU-118 with partially remaining charge can provide electrostatic force to anchor lattice water. Electrostatic force-driven lattice water bridging stabilizes the FJU-118 framework. The activated sample FJU-118a exhibits the third highest Brunauer–Emmett–Teller (BET)/Langmuir surface area (1860/2106 m2 g?1) among the reported indium MOFs. The absorption capacities for C2H2 and CO2 at 296/273 K are 88.6/155.1 cm3 g?1 and 35.6/66.9 cm3 g?1, respectively. The single crystal results show that the partially remaining charge on indium sites has an electrostatic force on the –C[triple bond, length as m-dash]C– bond of C2H2 molecules for the selective separation of C2H2/CO2 mixtures.

Graphical abstract: Electrostatic force-driven lattice water bridging to stabilize a partially charged indium MOF for efficient separation of C2H2/CO2 mixtures
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