Ab initio insights into the CO2 adsorption mechanisms in hydrated silica nanopores

JH Shi and T Zhang and SY Sun and L Gong, CHEMICAL ENGINEERING SCIENCE, 313, 121741 (2025).

DOI: 10.1016/j.ces.2025.121741

Understanding interfacial phenomena in confined systems is crucial for optimizing CO2 capture. We investigate CO2 adsorption in hydrated silica nanopores using grand canonical Monte Carlo, classical molecular dynamics (MD), and ab initio MD simulations. Excess adsorption isotherms show CO2 uptake decreases from 7.6 to 2.6 mmol/g as water content rises from 1 to 15 wt%. Adsorption kinetics reveal a bimodal process: rapid initial uptake followed by slower diffusion-limited adsorption. Classical MD shows reduced CO2 mobility with hydration, while density profiles indicate a shift in CO2 distribution from pore centers to surface regions. Ab initio MD captures proton transfer forming surface silanols (O-O distances: 2.4-2.5 & Aring;) and CO2 hydration yielding carbonates. Confined water acts as both a spatial competitor and reaction medium, offering molecular-level insights for designing carbon capture materials with quantum mechanical accuracy.

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