Bridging mesopores and amines via magnesium coordination for enhanced CO₂ capture: Insights from experiments and...

Amine-functionalized carbon materials exhibit high intrinsic selectivity for CO₂ capture, but their practical use is often limited by low capacity and insufficient stability. To address these constraints, this study proposes a metal-assisted strategy that enhances adsorption performance and regenerability while elucidating the cooperative interactions governing CO₂ capture in mesoporous carbon systems. Specifically, magnesium-doped mesoporous carbon (CMg) was prepared using SBA-15 as a hard template, followed by incorporation of polyethyleneimine (PEI) into the pore network; embedded Mg sites chelate with amine groups to construct a composite sorbent (C-Mg-PEI) featuring proximal active sites and a robust framework. Under 298 K and 1 bar, C-Mg-PEI achieves a static CO₂ uptake capacity of 1.23 mmol·g^-1. Under a dynamic feed containing 5 vol% CO₂, it exhibits a peak adsorption rate of 0.032 mmol·g^-1·min^-1 and reaches equilibrium within 12 min; after 20 adsorption-desorption cycles, the uptake remains 98 % of the initial value. At a regeneration temperature of 150 °C, achieving 95 % regeneration requires a specific energy consumption of approximately 2.77 GJ·t^-1 CO₂. Molecular dynamics simulations indicate that Mg doping strengthens the binding affinity between CO₂ molecules and amine functionalities, affording both physical confinement and chemical stabilization. ENVIRONMENTAL IMPLICATION: This study elucidates the efficient CO₂ adsorption and activation mechanism of PEI-based sorbents, where the bridging effect between Mg atoms and amine groups plays a pivotal role in stabilizing and activating CO₂ molecules. These findings provide theoretical guidance for the rational design of low-cost, regenerable sorbents and offer promising strategies to mitigate greenhouse gas emissions and advance carbon-neutral technologies.