K2CO3-mediated anti-oxidation of solid amine CO2 adsorbents: Local microenvironment regulation and radical pathway inhibition

K 2 CO 3 enhances oxidative stability of PEI-based adsorbent without sacrificing CO 2 uptake. • K 2 CO 3 regulates pore confinement and surface acid-base properties of the silica support. • In situ DRIFTS and mass spectrometry reveal suppressed PEI oxidative degradation. • EPR and 1 H NMR confirm reduced radical accumulation and restricted chain mobility. • DFT calculations reveal inhibited hydrogen abstraction by K 2 CO 3 charge regulation. Solid amine adsorbents are promising candidates for CO 2 capture, but their practical application is severely limited by oxidative degradation under high-temperature and oxygen-containing conditions. Conventional strategies mainly rely on chemical modification of amine species, which often compromises CO 2 adsorption capacity or introduces complex synthesis routes. Herein, we report a simple yet effective strategy using K 2 CO 3 as an inorganic additive to enhance the oxidative stability of polyethyleneimine (PEI)-based adsorbents. The introduction of K 2 CO 3 make total PEI content was comparable, but significantly improves CO 2 uptake retention after accelerated oxidation compared with the pristine counterpart. Systematic characterizations reveal that K 2 CO 3 regulates the local microenvironment by tuning pore confinement and surface acid-base properties of the silica support, while modifying the interfacial chemical environment of PEI. In situ DRIFTS and mass spectrometry analyses demonstrate that K 2 CO 3 suppresses the formation of carbonyl/imine-containing intermediates and reduces the evolution of volatile degradation products. Electron paramagnetic resonance and 1 H NMR relaxation results indicate that K 2 CO 3 inhibits radical accumulation and restricts polymer chain mobility. Density functional theory calculations further reveal that K 2 CO 3 reduced the thermodynamic driving force for hydrogen abstraction and modulates local charge distribution at reactive sites, suggesting suppressed radical initiation difficult. This work provides a simple inorganic additive strategy for constructing durable solid amine adsorbents, offering a general design principle for durable CO 2 capture applications under harsh oxidative conditions. Download: Download high-res image (380KB) Download: Download full-size image