Diffusion Dynamics of Volatile Organic Compounds into Integrated Surface-Supported Metal-Organic Frameworks Heterojunctions.

Surface-supported metal-organic frameworks (SURMOFs) have emerged as promising hybrid materials across diverse applications, including gas separation, energy storage, catalysis, and sensing. These capabilities are primarily associated with their high porosity and reasonable control over crystallinity. However, the diffusion of volatile organic compounds (VOCs) in these structures remains poorly understood, limiting their range in strategic applications. One significant challenge is developing effective integration approaches that enable precise control of molecular transport in these structures. In this work, we investigated the diffusion dynamics of various VOCs (methanol, ethanol, propanol, and hexane) into two-terminal devices based on a HKUST-1 thin-film SURMOF, using conventional photolithography and nanomembrane-origami technology. Systematic electrical responses (DC and AC) were monitored as precise and tunable tools for VOC differentiation. Our experimental results align with Gao's model, offering new insights into the diffusivity, permeability, pore accessibility, and intracrystalline diffusion lengths of VOCs within integrated HKUST-1 with thicknesses below 70 nm. These findings represent significant advances in understanding diffusion processes in monolithically integrated nanoporous materials, with potential implications for future innovations in molecular sensing and environmental monitoring technologies.