(507c) Laser-Irradiated Polybenzimidazole with Enhanced H2/CO2 Separation Properties

Polybenzimidazole (PBI) is a leading polymer for H₂/CO₂ separation for hydrogen purification and carbon capture, and a variety of techniques have been explored to improve its separation performance, enabling large-scale production of blue hydrogen. Laser-induced graphene (LIG) is a 3D porous carbon nanomaterial comprising porous multilayer graphene, and it can be generated by laser irradiation of polymers. Here, for the first time, we demonstrate that LIG can be generated from PBI, enhancing both H₂ permeability and H₂/CO₂ selectivity. The effect of the laser irradiation conditions and PBI film thickness was thoroughly characterized to elucidate the structure/property relationships. For example, one cycle of the CO₂ laser with a laser energy of 3.5 watts and a scanning speed of 15.7 cm/s increases the film thickness by 160% from 97 to 152 microns, H₂ permeability from 2.1 to 3.3 Barrer, and H₂/CO₂ selectivity from 12 to 56 at 35 °C; increasing the laser energy to 4 watts increases the film thickness to 162 microns, H₂ permeability to 5.8 Barrer, and H₂/CO₂ selectivity to 28. The LIG-PBI exhibits excellent stability, overcoming the permeability/selectivity tradeoff for H₂/CO₂ separation. This study showcases a facile and scalable way of engineering polymeric membranes at a nanoscale, representing a promising strategy to advance polymeric membranes for various molecular separations.