A windowed carbon nanotube membrane for CO₂/CH₄ gas mixture penetration separation: insights from theoretical...

A new class of species-permselective molecular sieves with functionalized nanowindows has been prepared by modifying the armchair single-walled carbon nanotubes (SWNTs) of a pillared graphene membrane, namely windowed carbon nanotube membrane. The mechanism and characteristics of the windowed carbon nanotube membrane for the selective separation of the CO₂/CH₄ gas mixture are comprehensively and deeply studied. Selective gas separation has a great dependence not only on the interaction of the gas adsorbing on the graphene membrane and inside the CNT channel but also with the energy barrier for the gas diffusing through the nanowindow. In all the functional nanowindows investigated, CH₄ is completely rejected by the N/F-modified nanowindows while maintaining extremely high CO₂ permeability. The CO₂ permeance of the nanowindows is as high as 10⁹ GPU. It emerged that these windowed carbon nanotube membranes are efficient species-selective molecular sieves possessing excellent CO₂/CH₄ selectivity and brilliant CO₂ capture capability.