Exciton Dissociation Strategy‐Guided Design of High‐Sensitivity COF‐Based Gas Sensors

ABSTRACT Exciton binding energy acts as a key modulator of the optoelectronic performance of semiconductor devices. Nevertheless, dedicated research addressing its impacts on gas sensing reactions for photoexcited semiconductor gas sensors is rarely reported. To uncover the intrinsic correlation between exciton effects and gas‐solid interfacial reactions, we rationally design Ni coordinated donor–acceptor (D–A) covalent organic frameworks (COFs), which effectively promote spatial charge rearrangement, weaken the strong Coulombic interaction of Frenkel excitons, and reduce the exciton binding energy ( E b ). This modification not only enhances NO 2 adsorption at Ni active sites but also enables the directional, rapid migration of photogenerated election toward target NO 2 molecules. As a result, the fabricated COF‐based micro‐electromechanical‐system (MEMS) sensor achieves a high sensitivity of 52 to 10 ppm NO 2 and an ultralow limit of detection of 84 ppt, representing a state‐of‐the‐art performance among the reported COF/MOF‐based gas‐sensing devices. Encouragingly, we also verify that this exciton engineering strategy enables versatile modulation of gas sensing kinetics, with broad applicability extending to metal sulfides, graphitic carbon nitride polymers, metal halides, metal oxides, and so on. As a proof‐of‐concept, we built a wireless robotic platform integrating MEMS sensors and AI algorithm, achieving 98.35% mixed‐gas discrimination accuracy for next‐generation hazardous gas detection technology.