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

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2022-05, Vol.1 (17), p.9363-9369
• Main Authors: Song, Qinhui, Yang, Yisi, Yuan, Furong, Zhu, Shiyuan, Wang, Jiaqi, Xiang, Shengchang, Zhang, Zhangjing
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d1ta10569h

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 C 2 H 2 /CO 2 separation. Two MOFs, [Me 2 NH 2 ]·[In(BDTA)] 5.5DMF·4H 2 O (FJU- 117 , BDTA is [4,4′,4′′,4′′′-([1,1′-biphenyl]-4,4′-diylbis(azanetriyl)) tetrabenzoic acid]) and [In(4Me-BDTA)·0.5H 2 O]·6DMF·2H 2 O (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 In 3+ 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- 118 a exhibits the third highest Brunauer-Emmett-Teller (BET)/Langmuir surface area (1860/2106 m 2 g −1 ) among the reported indium MOFs. The absorption capacities for C 2 H 2 and CO 2 at 296/273 K are 88.6/155.1 cm 3 g −1 and 35.6/66.9 cm 3 g −1 , respectively. The single crystal results show that the partially remaining charge on indium sites has an electrostatic force on the -C&z.tbd;C- bond of C 2 H 2 molecules for the selective separation of C 2 H 2 /CO 2 mixtures. Remaining charge on the indium sites of MOF FJU- 118 has an electrostatic force on the -C&z.tbd;C− bond of C 2 H 2 molecules for the selective separation of C 2 H 2 /CO 2 mixtures.