Atomic-Level Design of Electron-Rich Framework Oxygens Enhances Trace CO₂ Capture in Mordenite Zeolite Monoliths

The development of efficient physisorbents for trace CO₂ capture remains a critical challenge. Moving beyond conventional metal-CO₂ interaction strategies, we demonstrate a powerful alternative pathway through atomic-level engineering of zeolite oxygen electronic states. Incorporating Ce into the mordenite (MOR) framework generates electron-rich lattice oxygens and spatially polarized O^δ--Ce^δ+-O^δ- domains within the channels. These unique electronic features endow the resulting Ce-MOR with exceptional CO₂ uptake, even at high Si/Al ratios (∼8). Spectroscopic analyses and density functional theory (DFT) calculations reveal that strong Ce 4f-O 2p orbital coupling redistributes electron density, creating robust trapping sites. The electron-rich O^δ- atoms serve as primary binding centers, synergizing with adjacent Ce^δ+ to enable dual CO₂ adsorption pathways: C^δ+(CO₂)···O^δ- (framework) and O^δ-(CO₂)···Ce^δ+. Furthermore, by assembling Ce-MOR crystals into a binder-free monolith, we achieve enhanced mass transport and mechanical stability, translating the intrinsic adsorption advantages of Ce-MOR into superior dynamic CO₂ capture performance under realistic flow conditions. This work offers a novel perspective on designing practical, high-efficiency physisorbents by tailoring electron-rich anionic centers and integrating them into scalable monolithic architectures.