Pore-Size-Tuned Graphene Oxide Membrane as a Selective Molecular Sieving Layer: Toward Ultraselective Chemiresistors

Conventional graphene oxide (GO)-based gas membranes, having a narrow pore-size range of less than 0.3 nm, exhibit limited gas molecular permeability because of the kinetic diameters of most volatile organic and sulfur compound (VOCs/VSCs) molecules being larger than 0.3 nm. Here, we employ GO nanosheets (NSs) with a tunable pore-size distribution as a molecular sieving layer on two-dimensional (2D) metal oxide NSs-based gas sensors, i.e., PdO-sensitized WO₃ NSs to boost selectivity toward specific gas species. The pore size, surface area, and pore density of GO NSs were simply manipulated by controlling H₂O₂ concentration. In addition, the pore size-tuned GO NSs were coated on cellulose filtering paper as a free-standing nanoporous membrane. Holey GO membrane showed a highly selective H₂S permeability characteristic, exhibiting superior cross-selectivity to CH₃COCH₃ (0.46 nm), C₂H₅OH (0.45 nm), and C₇H₈ (0.59 nm) with larger kinetic diameters compared with H₂S (0.36 nm). Such pore-size-tuned GO nanoporous layer is scalable and robust, highlighting a great promise for designing low cost and highly efficient gas-permeable membrane for outstanding selective gas sensing platform.