Structural engineering in MOFs and COFs for challenging CO2 adsorption.

Crystalline porous frameworks, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) offer unprecedented opportunities for separation applications, yet their implementation under industrially challenging conditions requires sophisticated structural engineering. This perspective addresses the critical need to develop robust design strategies that enhance stability, selectivity, and functionality across different framework types, bridging fundamental research with practical separation challenges. We systematically survey key strategies for CO2 capture under humid environments, dilute concentrations (flue gas and direct air capture), and elevated temperatures/pressures. These include hydrophobic site engineering, humidity-enhanced adsorption, strong physisorption via pore confinement and electrostatic interactions, chemisorption with amines or hydroxides, and designs for thermal/mechanical stability such as metal hydrides, interpenetrated frameworks, and mixed-matrix membranes. This perspective not only advances the fundamental understanding of structural engineering for challenging CO2 capture but also guides the future design of next-generation porous materials toward real-world applications and negative emission goals.