A critical review of porous adsorbents for air separation: From fundamental insights to rational adsorbent design

Abstract

Air separation via selective adsorption using porous adsorbents offers energy-efficient alternatives to cryogenic distillation for producing high-purity O2 and N2. Adsorbent efficacy depends on balancing selectivity, durability, and performance consistency across varying conditions. This comprehensive review critically discusses the design and development of advanced porous adsorbents, including zeolites, metal–organic frameworks, and carbon molecular sieves, among other adsorbents, for air separation applications. We analyze their adsorption mechanisms, structure-performance relationships, and operational challenges such as moisture sensitivity, regeneration energy demands, and long-term stability under dynamic conditions. Recent advances enhance selectivity and capacity, but limitations persist in practical applications. By integrating mechanistic insights with performance benchmarks, this work identifies underexplored opportunities in molecular-level material design to guide next-generation adsorbents. This critical review bridges fundamental discoveries with adsorbent engineering, offering a roadmap to develop robust and effective adsorbents with the potential to replace energy-intensive cryogenic methods across various scales.