Unraveling the coupling effect of micropore confinement and functional sites of carbon-based adsorbents on flue gas CO2 adsorption: A machine learning study based on multi-scale simulations

• First demonstration of coupling effects between micropore confinement and functional dopants on CO₂ adsorption, diffusion, and optimal pore size. • A novel descriptor (free volume, V f ) quantifies steric effects from dopant-pore coupling, strongly correlating with CO₂ adsorption capacity. • Machine learning-guided workflow integrates multi-scale simulations to optimize micropore-dopant coupling modes for adsorbent design. • Synthesized carbon adsorbent achieves a leading CO₂ capacity of 4 mmol g⁻¹ at ambient conditions, 130% higher than non-optimized counterparts. • New design principles transcend traditional standalone pore/dopant engineering, advancing industrial flue gas CO₂ capture strategies. Carbon material is a type of promising adsorbent for flue gas CO 2 capture, where micropore and dopants are key functional units and intertwined with each other. Due to the difficulty in detaching micropore and functional sites, their effects on CO 2 adsorption are still in debate. Herein, we unravel coupling effects of micropore confinement and functional sites combining machine learning and multi-scale simulations. High-throughput Grand Canonical Monte Carlo (GCMC) simulations in combination with density functional theory calculations clarify that CO 2 adsorption mechanism under pore-dopant coupling is dependant on both micropore confinement environment and interaction type of CO 2 with functional sites. For basic dopants owning chemical interactions with CO 2 , adsorption potential driven by Lewis acid-base interactions dominate CO 2 adsorption behavior and the optimal pore size is distributed at 7 Å. For dopants that predominantly adsorb CO 2 by physisorption interaction, steric effect becomes a key factor influencing CO 2 adsorption behavior, which will result in a shift in optimal pore size for CO 2 adsorption from 7 to 8-10 Å and alter adsorption selectivity. In this case, new descriptor free volume ( V f ) was identified to describe coupling effects of micropore and functional sites. Guided by theoretical findings, we prepare carbon adsorbent with both heteroatom dopants and enlarged pore size, which exhibits leading-level CO 2 adsorption capacity of 4 mmol·g −1 at ambient condition, 130% higher than that without pore size optimization. This work demonstrates crucial role of micropore-dopant coupling mode on CO 2 adsorption, and provides new direction of developing high-performance carbon adsorbent beyond traditional standalone pore or doping engineering.