MIL-101s offer potential application for CH4/H-2 adsorption separation owing to its high porosity and excellent chemical stability. In this work, the grand canonical Monte Carlo method was employed to study the adsorption and separation of CH4/H-2 on a novel series of MIL-101s materials, such as MIL-101, MIL-101_NDC and new constructed MIL-101_R-7-BDC. The simulation results showed that CH4 was preferentially adsorbed over H-2 in all MIL-101s. The adsorption capacities of pure CH4 and H-2 on MIL-101_NDC were much higher than that in the other two MIL-101s, due to its largest S-acc (accessible surface area) and V-p (pore volume). The adsorption-site results suggested that the super-tetrahedras were the main adsorption site for CH4 molecules in all studied MIL-101s. Moreover, the additional benzene rings in MIL-101_R-7-BDC introduced several new CH4 adsorption sites which were close to the edge of large and small cages. Finally, we found that MIL-101_R-7-BDC had the highest CH4 selectivity. CH4 selectivity of MIL-101s was significantly affected by Delta q(st) (adsorption heat) and S-acc (accessible surface area) in terms of different organic ligands. (C) 2013 Elsevier Ltd. All rights reserved.