In this work, grand canonical Monte Carlo (GCMC) simulations were performed to evaluate the separation performance of covalent organic frameworks (COFs) compared with that of metal-organic frameworks (MOFs) for CH4/CO2/H-2 mixtures. The simulation results show that the adsorption selectivities of COFs and MOFs are similar. The electrostatic contribution of framework charges in COFs should be taken into account, although it is smaller than that in MOFs. In addition, the present work shows that the ideal adsorbed solution theory (IAST) is applicable to most COFs.