- A new type of cross-selective gas sensor has been developed, based on a vapor-induced capacitance modulation of chemically-functionalized porous graphene oxide (pGO). The dielectric pGO matrix was assembled in situ upon an electrode surface via a combined room-temperature annealing/freeze-drying process. Extraordinary vapor sensing properties are demonstrated, specifically extremely high sensitivity, wide dynamic range, rapid response and recovery times, fidelity, and detection of a broad range of molecular targets. The excellent sensing capabilities correspond to the open porous framework of pGO and high surface area within the pores, as well as molecular interactions between the vapor molecules and functional units displayed on the pGO framework. Array-based identification of different vapors is demonstrated via functionalization of the pGO scaffolds with distinct chemical residues.