Water boosted CO_(2)/C_(2)H_(2)separation in L-arginine functionalized metal–organic framework

The separation of CO_(2)/C_(2)H_(2)mixture by CO_(2)-selective sorbents is an energy-efficient C_(2)H_(2)purification technique,but is strategically challenging due to their similar molecular size and physicochemical properties.Meanwhile,water is inevitable in CO_(2)/C_(2)H_(2)mixture and it is usually a significant barrier because of its competitive adsorption with CO_(2).To address this challenge,herein,we report the first example of metal–organic framework(MOF)that exhibits water-boosted CO_(2)adsorption and CO_(2)/C_(2)H_(2)separation by anchoring L-arginine(ARG)on the Zr6 cluster of MOF-808.The CO_(2)affinity and capacity in the resulting MOF-808-ARG are markedly facilitated by the presence of water,while the C_(2)H_(2)adsorption is significantly suppressed.Specifically,CO_(2)adsorption capacities in adsorption isotherm and breakthrough measurement are increased to 143%and 184%,respectively.In addition,the wet MOF-808-ARG exhibits the record CO_(2)/C_(2)H_(2)selectivity of 1,180 under zero coverage.Breakthrough experiments reveal that CO_(2)/C_(2)H_(2)mixture can be completely separated and the result of mass spectrometry indicates that the C_(2)H_(2)purity in the outlet is up to 99.9%.In situ infrared(IR)results and density functional theory(DFT)calculations reveal the water-promoted CO_(2)adsorption mechanism that the formation of bicarbonate products in the presence of water is thermodynamically and kinetically more favorable than that without water.Moreover,MOF-808-ARG also possesses excellent water stability and excellent regeneration of CO_(2)adsorption.This work provides a new paradigm by transforming the negative effects of water into positive ones for CO_(2)/C_(2)H_(2)separation.