Phase-Programmed Charge Routing Governs Kinetic and Thermodynamic Molecular Selectivity for Chemiresistive Sensors.

Controlling molecular selectivity in chemiresistive gas sensors remains a fundamental challenge, particularly for chemically analogous analytes that generate indistinguishable electronic responses. Here, we demonstrate that polymorph-engineered MoS2/SnO2 heterointerfaces establish a programmable molecular recognition platform for selective volatile amine detection. By tuning the 1T/2H phase distribution within MoS2/SnO2 nanorod heterostructures, distinct sensing pathways emerge for chemically similar molecules. Specifically, 1T-enriched heterostructures preferentially detect ammonia (NH3), whereas 2H-dominated architectures selectively respond to triethylamine (TEA). Neural Network Potential Molecular Dynamics (NNP-MD) simulations reveal that this selectivity originates from phase-dependent charge routing at the heterointerface, which governs the coupling between molecular rotational dynamics, surface reaction kinetics, and adsorption thermodynamics. Spectroscopic and gas-phase analyses indicate that 1T-rich interfaces promote kinetically driven catalytic activation of NH3, generating reactive intermediates that transiently oxidize Mo centers. In contrast, 2H-dominated interfaces favor thermodynamically stabilized dipole-mediated adsorption of TEA, producing a distinct electronic response with minimal surface oxidation. The optimized sensors achieve sub-parts-per-billion detection limits (0.5 ppb for NH3 and 0.6 ppb for TEA) and maintain stable operation under high humidity. Practical applicability is demonstrated through real-time monitoring of volatile amine emissions during pomfret fish spoilage under ambient storage. This work introduces a new paradigm in phase-engineered heterointerfaces as a generalizable materials-design strategy for programming intrinsic kinetic and thermodynamic selectivity for next-generation chemical sensors.