Research Progress on Clay Mineral−based Adsorbents for CO₂ Capture

Clay minerals are promising candidates for CO₂ capture owing to their natural abundance, low cost, and structurally tunable properties. This review provides a systematic overview of recent advances in clay mineral−based adsorbents for CO₂ capture. Key modification strategies, including acid/base treatment, metal ion doping, ionic liquid incorporation, pillar intercalation, and the synthesis of organic–inorganic hybrid composites, are examined in terms of their impacts on the structure and adsorption behavior of clay minerals. Special emphasis is placed on amine−functionalized clay adsorbents, with a comparative analysis of three main functionalization approaches: impregnation, grafting, and direct synthesis. The CO₂ adsorption performance, selectivity, and cycling stability of amine−modified montmorillonite, kaolinite, and halloysite are discussed along with their underlying mechanisms. Finally, current challenges related to amine dispersion, structural stability, and scalable application are addressed. Perspectives are offered on achieving efficient and low−energy CO₂ capture through synergistic modification strategies, green synthesis routes, and rational structural design. This work aims to inform the high−value utilization of clay minerals and contribute to practical solutions for greenhouse gas mitigation.