Study of supramolecular organic frameworks for purification of hydrogen through molecular dynamics simulations

The efficiency of proton exchange membrane fuel cells (PEMFCs) is heavily dependent on hydrogen purity. The production of hydrogen using methanol releases gases such as CO2 and CO, and hydrogen purification is particularly important. In this study, the performance of hydrogen purification (H2/CO2, H2/CO, and H2/CO2/ CO) of three supramolecular organic frameworks (SOF-8, SOF-9a, and SOF-10a) with similar structures and different pore sizes and dimensions (two-dimensional (2D) and three-dimensional (3D)) were comprehensively investigated by molecular dynamics simulations and Grand Canonical Monte Carlo simulations. The monolayer, AA and AB stacked SOFs membranes were investigated. The results show that monolayer membranes exhibited high H2 permeability but low CO2 interception. AA-stacked SOF-10a and AB-stacked SOF-8 and SOF-10a can achieve 100 % separation of H2 from both CO2 and CO, with a minimum H2 permeability of 0.3 x 106 GPU and a maximum of up to 0.66 x 106 GPU in the H2/CO2 separation system, which is nearly 5 orders of magnitude higher than the industry standard. Microscopic analyses indicate that 3D SOFs (SOF-9a and SOF-10a) exhibit stronger interactions with CO2, while still maintain high H2 permeability in different stacking modes.