Dicationic liquid containing alkenyl modified CuBTC improves the performance of the composites: Increasing the CO2 adsorption effect

Abstract Two novel di-cation liquid-copper-based Cu-BTC (DILs/CuBTC) were obtained by modifying CuBTC with dicationic ionic liquids. 3,3'-(butane-1,4-diyl)bis(1-methyl-1H-imidazol-3-ium)bromide([C4(im)2]Br2) and 3,3'-(butane-1,4-diyl)bis(1-vinyl-1H-imidazol-3-ium)bromide([C4(Vim)2]Br2) were used to modify CuBTC. SEM, XRD, FTIR, BET, and TG characterized the morphology, structure, and thermal stability of the DILs/CuBTC. The results show that hydrogen bonding recombines DILs and CuBTC, and the DILs modification does not destroy the original framework structure of CuBTC. The adsorption properties and mechanism of the DILs/CuBTC for CO2 adsorption were also studied. DILs / CuBTC has a better CO2 adsorption effect than CuBTC, because the long chains of DILs and newly formed hydrogen bonds provide new active sites. Studies have found DIL-2/CuBTC that CuBTC modified by [C4(Vim)2]Br2 has the largest specific surface area and exhibits the best adsorption performance. It may be that the alkenyl groups on DILs can strengthen the interaction between DILs and CuBTC through π-π force, conducive to the dispersion of DIL and the formation of the composite. Time, adsorbent dose, and CO2 concentration effects on the adsorption of CO2 were studied. At 293 K, the maximum theoretical adsorption capacity (qm) of DIL-2/CuBTC for CO2 is 44.93 mmol g-1, 114.67% higher than CuBTC. Both the pseudo-second-order model and Freundlich model fit the adsorption data well. DIL-2/CuBTC has excellent repeatability and cyclic stability, it can be used as an effective adsorbent for CO2 and other toxic gases.