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 WO NSs to boost selectivity toward specific gas species. The pore size, surface area, and pore density of GO NSs were simply manipulated by controlling HO 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 HS permeability characteristic, exhibiting superior cross-selectivity to CHCOCH (0.46 nm), CHOH (0.45 nm), and CH (0.59 nm) with larger kinetic diameters compared with HS (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.