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

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-1 for CO2vs. 47.81 kJ mol-1 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 prediction or an idealized, defect-free sheet that surpasses 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 for future separation technologies.