Adsorption and diffusion of CO₂ and CH₄ in covalent organic frameworks: an MC/MD simulation study

ABSTRACT

Covalent organic frameworks (COFs) are a promising gas separation material which have been developed recently. In this work, we have used grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations to investigate the adsorption and diffusion properties of CO₂ and CH₄ in five recent synthesised COF materials. We have also considered the properties of amino-modified COFs by adding –NH₂ group to the five COFs. The adsorption isotherm, adsorption/diffusion selectivity, self/transport diffusion coefficients have been examined and discussed. All of the five COFs exhibit promising adsorption selectivity which is higher than common nanoporous materials. An S-shaped adsorption isotherm can be found for CO₂ instead of CH₄ adsorption. The introduction of –NH₂ group is effective at low pressure region (<200 kPa). The diffusion coefficients are similar for TS-COFs but increase with the pore size for PI-COFs, and the diffusion coefficients seem less dependent on the –NH₂ groups.

KEYWORDS:

• Covalent organic frameworks
• grand canonical Monte Carlo
• molecular dynamics
• adsorption
• separation

Additional information

Funding

This work was supported by National Natural Science Foundation of China: [Grant Numbers 21506051, 21776070, 91334203]; Shanghai Pujiang Program: [Grant Number 15PJ1401400]; National Natural Science Foundation of China for Innovative Research Groups: [Grant Number 51621002]; National Basic Research Program of China: [Grant Number 2013CB733501]; Open Project of the State Key Laboratory of Chemical Engineering: [Grant Number SKL-Che-15C05]; 111 Project of China: [Grant Number B08021].