Catalyst-dependent pore engineering of waste plastic-derived supports for solid amine adsorbents in CO2 capture

Controlling CO 2 emissions is paramount for mitigating global warming. Developing solid amine adsorbents with high CO 2 adsorption capacity using minimal active species is essential for advancing carbon capture technology. In this study, waste polystyrene foam was utilized as the raw material to synthesize waste-derived hyper-cross-linked polymer (WHCP) supports via Friedel-Crafts alkylation using different catalysts (FeCl 3 and AlCl 3 ). Polyethyleneimine (PEI) was then impregnated into the supports (WHCP/Fe and WHCP/Al) to prepare waste-derived resin-based solid amine adsorbents. The adsorption performance of these adsorbents was systematically evaluated under varying amine loadings (10–50 %) and temperatures (30–105 °C). Although WHCP/Fe possessed a larger specific surface area and pore volume, WHCP/Al exhibited a higher proportion of mesopores and macropores, which facilitated the loading of the bulky amine molecules of PEI. This resulted in PEI-modified WHCP/Al possessing a more favorable pore structure and improved amine dispersion. The PEI-modified WHCP/Al exhibited excellent adsorption performance and favorable kinetic characteristics, maintaining a prolonged rapid adsorption phase (1.62–2.47 min) and a high peak adsorption rate of 8.10 mmol CO 2 /(g·min), along with a stable and relatively short half-time. Herein, 50 %-WHCP/Al demonstrated superior adsorption performance, achieving an optimal CO 2 adsorption capacity of 3.00 mmol/g at 75 °C and maintaining high adsorption capacity across a broad temperature range. Furthermore, it exhibited a capacity decay rate of only 10.22 % after 10 adsorption-desorption cycles. This study provides a theoretical foundation for the recycling of waste polystyrene and application in cost-effective carbon capture technologies.