Simulation Study of Mass Transfer Characteristics of CH4/CO2 Separation in Multiple Types of Covalent Organic Framework Membrane Materials

Covalent organic framework (COF) membrane materials are being increasingly utilized in gas separation processes due to their low-carbon, clean, and efficient properties. These materials are expected to have large-scale industrial applications in natural gas clean-up and separation processes. The separation effects of COFs materials vary for the CO2 membrane separation process, which has a significant impact on gas recovery. This paper aims to compare the mass transfer patterns of different COFs to separate CO2 and to expose the mechanism of separation. Employing a combination of Monte Carlo (GCMC) and molecular dynamics (MD) methods, this paper analyzes the mass transfer behaviors of CO2 separation from CH4/CO2. The study also examines the thermodynamic parameters, such as separation temperature, separation pressure, and gas components, to reveal the properties of CO2 separation from different COFs and the transport rules of gas molecules at the microscopic level. The findings suggest that pore size, CO2 concentration, and lower temperature environment contribute to the ability of CO2 adsorption. Additionally, COFs with oxygen-containing groups (NUS-2, COF-5, etc.) have better diffusion separation ability, and the AA stacking forms should be maintained during the process of completing the diffusion separation CO2. This paper could provide the essential basis for the design and adjustment of the structure of COFs and the enhancement of the gas membrane separation technology.