Structure–Electronic Synergy in Bifunctionalized Zeolite Enables Fast CO ₂ Capture at Indoor Levels

Elevated CO2 levels in confined spaces such as large conference rooms and vehicle cabins (∼1000 ppm) increasingly compromise indoor air quality and human health, yet the development of solid adsorbents effective under such moderate concentrations remains challenging. Herein, we present a synergistic amine-bifunctionalization strategy to rationally engineer ZSM-5 zeolites for highly efficient CO2 capture under indoor-relevant conditions. Surface silanization with 3-aminopropyltriethoxysilane (APTES) generates stable anchoring sites while modulating pore accessibility, and subsequent tetraethylenepentamine (TEPA) impregnation introduces a high density of chemically active amines. The resulting bifunctionalized ZSM-5 exhibits an exceptional CO2 uptake of 7.82 mmol·g–1 at ambient temperature, which is 2.1 times higher than that of pristine ZSM-5 (3.78 mmol·g–1), together with rapid adsorption kinetics and outstanding regeneration stability over multiple cycles. Combined experimental characterization and density functional theory calculations reveal that the bifunctionalized interface promotes strong charge transfer and electronic coupling between CO2 and surface amine sites, shifting the adsorption mechanism from weak physisorption on pristine ZSM-5 to chemisorption-dominated interactions accompanied by pronounced band gap narrowing. These results demonstrate a structure-electronic synergy that enables efficient CO2 capture, providing mechanistic insights for the rational design of zeolite-based adsorbents for indoor air purification and confined-space carbon management.