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Pore environment engineering in metal–organic frameworks for efficient ethane/ethylene separation

Wang, Xun, Niu, Zheng, Al-Enizi, Abdullah M., Nafady, Ayman, Wu, Yufang, Aguila, Briana, Verma, Gaurav, Wojtas, Lukasz, Chen, Yu-Sheng, Li, Zhong, Ma, Shengqian
Journal of materials chemistry A 2019 v.7 no.22 pp. 13585-13590
adsorbents, adsorption, coordination polymers, desorption, ethane, ethylene, moieties, nickel, porous media
Selective adsorption of trace amounts of C₂H₆ from bulk C₂H₄ is a significantly important and extremely challenging task in industry, which requires an adsorbent with specific pore properties. Herein, we describe a strategy for adjusting the pore environment of metal–organic frameworks (MOFs) by introducing different amounts of methyl groups in the channel to enhance the guest–host interaction between C₂H₆ and the framework. To prove this concept, 2,3,5,6-tetramethylterephthalic acid (TMBDC) was deliberately added to a microporous MOF, Ni(BDC)(DABCO)₀.₅, affording a series of mixed-ligand materials, Ni(BDC)₁₋ₓ(TMBDC)ₓ(DABCO)₀.₅ (x = 0, 0.2, 0.45, 0.71, 1), having different pore environments. Significantly, these mixed-ligand materials demonstrated improved performance in terms of the adsorption capacity of C₂H₆ and C₂H₄ with an unprecedented C₂H₆ uptake of 2.21 mmol g⁻¹ for Ni(TMBDC)(DABCO)₀.₅ at 0.0625 bar and 298 K. With the best theoretical C₂H₆/C₂H₄ selectivity predicted by IAST, Ni(TMBDC)(DABCO)₀.₅ exhibited effective separation of C₂H₆/C₂H₄ (1/15, v/v) and great recyclability in five consecutive adsorption/desorption cycles throughout the breakthrough experiment.