Controlling Host–Guest Interactions in Poly(ethylenimine) Impregnated Silica Adsorbents for CO2 Capture

Abstract

Poly(ethylenimine)-impregnated silica (PEI/SiO₂) adsorbents have garnered significant attention as scalable and sustainable solutions for carbon dioxide (CO₂) capture owing to their high adsorption capacity, facile synthesis, and cost-effectiveness. Despite continued research efforts, several critical challenges remain to be addressed to fully optimize these materials—namely, enhancing CO₂ adsorption capacity, improving adsorption kinetics, minimizing regeneration (desorption) energy requirements, and ensuring long-term operational stability. This review first examines the fundamental properties of PEI as a CO₂ adsorbent and delineates the primary barriers to its practical deployment. Subsequently, key strategies to modulate host–guest interactions are discussed, with emphasis on: (1) tailoring the pore structure of silica supports, (2) optimizing surface chemistry to improve PEI dispersion, (3) incorporating additives to regulate host–guest interactions, and (4) chemically modifying PEI to enhance stability and the heat of adsorption. Finally, critical future directions are outlined for advancing PEI/SiO₂ adsorbents, with a particular focus on addressing the engineering challenges essential for large-scale implementation. By integrating rational material design with process-level optimization, this review highlights viable pathways for the effective translation of these adsorbents into practical CO₂ capture technologies.