Tuning secondary building unit of Cu-BTC to simultaneously enhance its CO2 selective adsorption and stability under moisture

Abstract We report a bifunctional SBU-tuning strategy that simultaneously enhances the selective CO 2 adsorption capacity of Cu-BTC and its structural stability under moisture. A series of Gly@Cu-BTCs were prepared by grafting glycine (Gly) to the secondary building units (SBUs) of the commercially available Cu-BTC through the nano-seed assistant ultrafast room temperature synthesis. N 2 isotherms evidenced higher BET specific surface area and pore volume of Gly@Cu-BTCs than that of Cu-BTC. Hence, Gly 0.3 @Cu-BTC exhibited a superior CO 2 capacity of 5.4 mmol/g at ambient conditions, which is 12% higher than that of Cu-BTC. Besides, the adsorptive selectivity of Gly 0.3 @Cu-BTC for the equimolar CO 2 /CH 4 and CO 2 /N 2 mixtures was separately up to 8.53 and 59.38, being 11% and 15% higher compared to that of Cu-BTC. More importantly, the stability of Gly 0.3 @Cu-BTC against moisture was improved. After 10 days’ exposure in 55% relative humidity, Gly 0.3 @Cu-BTC preserved 80% of its original CO 2 capacity, while only 9% CO 2 capacity remained for Cu-BTC. In addition, negligible CO 2 capacity loss of Gly 0.3 @Cu-BTC was observed in the subsequent 10 days in moisture after the initial exposure. Gly 0.3 @Cu-BTC exhibited excellent regenerability, and its CO 2 desorption efficiency reached up to 98% based on the consecutive adsorption-desorption cycles. The origination of the improved stability under moist of Gly 0.3 @Cu-BTC was interpreted with DFT calculation. The bifunctional SBU-tuning strategy demonstrated in this work enables the potential adsorptive separation application of Cu-BTC under moist working condition.