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

Abstract

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.