Postsynthetic Strategy To Prepare ACN@Cu-BTCs with Enhanced Water Vapor Stability and CO2/CH4 Separation Selectivity

Cu-BTC, a commercially available MOF with great potential in gas adsorption and separation, is vulnerable to moisture, hindering its practical application. We propose a postsynthetic strategy to prepare ACN@Cu-BTCs with enhanced water vapor stability and CO2/CH4 selectivity. Successful grafting of ACN was evidenced by FT-IR spectra, which completely inhibited the moisture-induced adsorptive capacity degeneration of ACN(1/1)@Cu-BTC at RH = 55% for CO2 capture. The water vapor stability experiments showed that after being exposed to 55% RH for 20 days, Cu-BTC lost its crystallinity and CO2 adsorption capacity, while ACN(1/3)@Cu-BTC preserved 88% of its original CO2 capacity. In addition, ACN(1/3)@Cu-BTC showed a high CO2 capacity of 4.32 mmol/g under ambient conditions and inherited the decent CO2/CH4 adsorption selectivity from Cu-BTC. DFT calculation ascribed such an enhanced water vapor stability to the protection of Cu sites by ACN, which is worth further exploitation in enhancing the water vapor stability of other MOFs with unsaturated metal sites.