Waste-derived geopolymer-zeolite supported TEPA sorbents: Enhancing CO2 capture kinetics and stability via Ni coordination

The severe self-aggregation and instability of polyamines at high loadings remain major mass-transfer limitations in solid amine sorbents. To overcome this kinetic limitation, we propose a molecular-level regulation strategy by incorporating trace Ni (1 wt%) into tetraethylenepentamine (TEPA) confined within a hierarchical porous geopolymer-zeolite framework. Rather than acting as a conventional promoter, the intentionally introduced Ni forms specific Ni-TEPA coordination complexes, which significantly disrupted the intermolecular hydrogen-bonding network and inhibited polyamine aggregation. Consequently, the Ni-modified sorbent effectively alleviated diffusion resistance, exhibiting substantially improved amine accessibility and accelerated adsorption kinetics. Density functional theory (DFT) combined with spectroscopic analyses revealed that Ni coordination systematically reduced the electron density around the amine nitrogen sites, substantially lowering the apparent adsorption activation energy to 8.28 kJ/mol. Under simulated post-combustion conditions (15 vol% CO 2 , 70 °C), the optimized sorbent achieved a high CO 2 uptake of 3.92 mmol/g and retained 99.75% of its initial capacity after 10 cycles. Furthermore, utilizing waste-derived zeolite-geopolymer (from municipal solid waste incineration and coal fly ash) as the robust support yields a potentially attractive manufacturing cost of 158.99 ¥/kg, providing a sustainable and scalable chemical engineering approach for industrial flue gas treatment.