Immobilization of H2O in Diffusion Channel of Metal-Organic Frameworks for Long-Term CO2 Capture from Humid Flue Gas.

Utilizing physisorption for CO2 capture in humid flue gas presents challenges, with H2O molecules either damaging the adsorbent or competing with CO2 for adsorption, compromising long-term stability. Herein, a counter-intuitive strategy is proposed to address this issue by immobilizing H2O into metal-organic framework (TYUT-ATZ, TYUT = Taiyuan University of Technology, ATZ = 3-amino-1,2,4-triazole) as binding sites for CO2 capture from humid airflow. Through tailoring the -NH2 group numbers and pore sizes creates ingenious H2O sites, preserving CO2 adsorption space and enhancing CO2 adsorption interactions in 1D channels. The well-constructed TYUT-ATZ-β demonstrates a high CO2 adsorption capacity (62.7 cm3 cm-3) at 0.15 bar and outstanding CO2/N2 (15/85) selectivity (2031) at 298 K, while also exhibits the highest CO2/H2O uptake ratio in humid flue gas due to its excellent water stability and unique H2O site. Consequently, it shows top-performing CO2 enrichment ability with easy regeneration in long-term separation experiments (over 100 cycles) under high-humidity (75% RH). Gas adsorption isotherms, single-crystal analysis, selectivity calculations, and contrastive breakthrough experiments comprehensively validate this artful H2O immobilization strategy in MOFs for efficient CO2 capture in humid flue gas, satisfying the application requirements of high selectivity, rapid regeneration, and long-term stability.