Molecular Simulations of MXene Nanosheet-Based Membranes for Syngas Separation

In various industrial applications focusing on environmental sustainability, the purification of H2 from CO2-containing streams is crucial. Membrane-based separation processes are preferred over other gas separation techniques due to their superior efficiency and selectivity and lower energy consumption. Membranes composed of inorganic nanoporous materials, known for their uniform pore size distribution and high permeability, exhibit remarkable gas separation performance. Recently, two-dimensional (2D) nanomaterials with high surface area and tunable functional groups have gained attention for membrane-based gas separation applications, owing to their thermal and mechanical durability. Therefore, we carried out a simulation study at the nanoscale level encompassing multiple analytical viewpoints of 2D MXene membranes: (i) A collection of 730 MXene structures was evaluated for single gas H2/CO2 separation, and 700 of these surpassed the Robeson upper bound, indicating their significant potential for replacing conventional polymeric membranes. Moreover, VCrNF2, MoWCF2, Y2NO2, and Sc2NO2 nanomaterials were listed as potential membranes according to the predefined ranking criteria. (ii) The performance of mixed matrix membranes (MMMs) made of five different polymers and all MXene nanomaterials was calculated with Maxwell's model. (iii) The effect of interlayer distance of MXene nanosheets on H2/CO2 separation was examined over the top four MXene nanomaterials and experimentally highly studied Ti2CO2 MXene. The optimum interlayer distance was defined as 5.5 Å for effective separation. (iv) Finally, Y2NO2 and Ti2CO2 MXene membranes were compared in terms of concentration polarization. Y2NO2 is more susceptible to CO2-related concentration polarization, which hinders CO2 transport and improves H2/CO2 separation in single gas measurements. By examining MXene membranes for H2/CO2 separation in multiple aspects, we aimed to demonstrate their potential and further guide the experimental studies.