Moisture-Promoted, Defect-Rich UiO-67/TiO ₂ Nanotube Heterojunctions for ppb-Level H ₂ S Detection under Ambient Conditions

Room-temperature (RT) operation under ambient humidity remains a fundamental impediment to high-performance metal-oxide-semiconductor (MOS) chemiresistive sensors. Here, we convert humidity from a liability into an asset by conformally growing defect-rich UiO-67(Zr) nanoparticles on anodic TiO₂ nanotube arrays (TiO₂NT@U7_R) through a one-step ligand-acetic acid modulation strategy. The resulting organic-inorganic heterojunction couples Zr(III)-induced oxygen vacancies with the porous architecture of MOFs, enabling water molecules to promote charge transport and surface chemistry rather than suppressing them. The resulting TiO₂NT@U7_R delivers a response of ∼194 toward 10 ppm of H₂S at 75%RH, an ultralow detection limit of ∼0.04 ppb, and stable performance over 30 days at RT. Reliable H₂S quantification in exhaled gases and the fabrication of a portable prototype highlight its application potentials. This work offers a scalable blueprint for the humidity-tolerant, reproducible manufacture of next-generation MOS chemiresistive sensors.