The Reinforced Separation of Intractable Gas Mixtures by Using Porous Adsorbents

This review focuses on the mechanism and driving force in the intractable gas separation using porous adsorbents. A variety of intractable mixtures have been discussed, including air separation, carbon capture, and hydrocarbon purification. Moreover, the separation systems are categorized according to distinctly biased modes depending on the minor differences in the kinetic diameter, dipole/quadruple moment, and polarizability of the adsorbates, or sorted by the varied separation occasions (e.g., CO₂ capture from flue gas or air) and driving forces (thermodynamic and kinetic separation, molecular sieving). Each section highlights the functionalization strategies for porous materials, like synthesis condition optimization and organic group modifications for porous carbon materials, cation exchange and heteroatom doping for zeolites, and metal node-organic ligand adjustments for MOFs. These functionalization strategies are subsequently associated with enhanced adsorption performances (capacity, selectivity, structural/thermal stability, moisture resistance, etc.) toward the analog gas mixtures. Finally, this review also discusses future challenges and prospects for using porous materials in intractable gas separation. Therein, the combination of theoretical calculation with the synthesis condition and adsorption parameters optimization of porous adsorbents may have great potential, given its fast targeting of candidate adsorbents and deeper insights into the adsorption forces in the confined pores and cages.