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

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 7; no. 22; pp. 13585 - 1359
• Main Authors: 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
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2019; Royal Society of Chemistry (RSC)
• Subjects: Adsorption; Crystallography; Ethane; Ligands; Metal-organic frameworks; Metals; NMR; Nuclear magnetic resonance; Recyclability; Selective adsorption; Selectivity; Separation; Single crystals
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta02822f

Selective adsorption of trace amounts of C 2 H 6 from bulk C 2 H 4 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 C 2 H 6 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 C 2 H 6 and C 2 H 4 with an unprecedented C 2 H 6 uptake of 2.21 mmol g −1 for Ni(TMBDC)(DABCO) 0.5 at 0.0625 bar and 298 K. With the best theoretical C 2 H 6 /C 2 H 4 selectivity predicted by IAST, Ni(TMBDC)(DABCO) 0.5 exhibited effective separation of C 2 H 6 /C 2 H 4 (1/15, v/v) and great recyclability in five consecutive adsorption/desorption cycles throughout the breakthrough experiment. Methyl groups are introduced on the pore walls of a metal-organic framework to enhance the separation performance of C 2 H 6 /C 2 H 4 .