Molecular Programming of Core-Shell Oxide Interfaces to Decouple Humidity Interference in Gas Sensing

Humidity-tolerant gas sensing remains a long-standing challenge, as interfacial adsorption chemistry and charge transport processes in metal oxides are intrinsically coupled to ambient humidity. Here, we introduce a molecular programming strategy for oxide interfaces enabled by polyoxometalate (POM)-assisted coaxial electrospinning, in which preassembled metal-oxygen clusters function as chemically addressable building units rather than conventional ionic precursors. By spatially encoding distinct POMs into the core and shell of electrospun nanofibers and inducing controlled solid-state conversion, hierarchical oxide architectures with structurally coherent and chemically programmable heterointerfaces are constructed. POM clusters enable interfacial engineering during oxide formation owing to their well-defined nuclearity, coordination geometry, and intrinsic acidity, which allow modulation of the surface Lewis acidity, defect chemistry, and band alignment beyond conventional single-metal salt precursors. Consequently, the POM-derived MoO3 shell establishes a preferential adsorption environment for basic amine molecules while mitigating water adsorption and hydroxyl-related surface processes. In parallel, the WO3 core serves as an electronically continuous transport scaffold, ensuring the efficient transduction of interfacial charge redistribution. This separation of surface adsorption and bulk charge transport enables a sensing mechanism primarily governed by surface chemistry, resulting in humidity-tolerant and stable triethylamine responses across a wide range of humidity. Beyond gas sensing, this work positions POM clusters as a general platform for molecular-level programming of oxide interfaces, offering new opportunities for designing functional materials with environmentally robust interfacial behavior.