Competitive adsorption-driven CO2/N2 separation in monolayer fullerene membranes with funnel-shaped pores

Abstract

Efficient CO₂/N₂ separation is critical for advancing carbon capture technologies to mitigate climate impacts from industrial emissions. In this study, we model an idealized, defect-free monolayer fullerene membrane featuring funnel-shaped nanochannels to investigate the CO₂/N₂ separation mechanism by combining first-principles calculations and molecular dynamics simulations. The unique nanochannel geometry induces a dual mechanism (1) competitive adsorption preferentially enriches CO₂ at the membrane surface, and (2) nanopore confinement creates a pronounced difference in free energy barriers for translocation (25.89 kJ/mol for CO₂ vs. 47.81 kJ/mol for N₂), facilitating highly selective CO₂ permeation. This synergistic interplay yields exceptional performance, with a CO₂/N₂ selectivity of 3564 and a CO₂ permeance of 2.11 × 10^-5 mol m^-2 s^-1 Pa^-1 at 300 K, representing an upper-bound predictions or an idealized, defect-free sheet that surpassing conventional membrane benchmarks. Additionally, rotational density of states analysis reveals that both CO₂ and N₂ exhibit notably enhanced high-frequency rotational modes when traversing the funnel-shaped nanochannels, but stronger rotational constraints significantly restrict N₂ diffusion compared to CO₂. These findings highlight the promise of monolayer fullerene membranes as sustainable, high-performance solutions for gas separation, and provide mechanistic insights for the rational design of advanced nanochannel architectures in future separation technologies.