Tunable Gas-Liquid Separation by Surface Charge Modifications: Toward Membrane-Based Carbon Capture and Detection

Carbon capture plays a crucial role in both climate mitigation and carbon-based analytical technologies involving gas-liquid separation. Nanoporous graphene membranes (NGMs) provide an atomically thin platform for studying CO₂ transport. Here, using all-atom molecular dynamics simulations, we investigate the CO₂ transport mechanism through NGMs at the gas-liquid interface. We show that pore-edge electrostatics strongly modulate interfacial hydration. Surface charges and polar functional groups promote water accumulation near the pore mouth and suppress CO₂ transport, whereas hydrophobic pores reduce water blockage and enhance permeance. By comparing pristine, H-terminated, charged, and functionalized pores, we identify interfacial hydration as a key factor governing transport at the gas-liquid interface. Contrary to the common expectation that stronger electrostatic interactions facilitate CO₂ transport, our results show that enhanced electrostatics strengthen interfacial hydration and thereby suppress transport, limiting the performance of carbon-based analytical technologies that require precise detection.