Tuning Selectivity of SnS₂-Based Gas Sensor via In Situ Growth of 2D Metal-Organic Frameworks for Molecular Sieving

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have gained significant attentions as advanced materials for gas sensing platforms due to their high surface area, abundant active edge sites, and mechanical flexibility. However, their lack of selectivity, as they exhibit strong responses to various gases, limits their effectiveness for gas discrimination. In this study, we present a method to enhance the gas selectivity of SnS₂-based gas sensors through the in-situ growth of breathable zeolitic imidazolate framework-leaf (ZIF-L). ZIF-L allows selective permeation of the target gas, H₂S, while blocking interfering gases such as C₃H₉N, NH₃, and volatile organic compounds. The resulting ZIF-L/SnS₂ sensor exhibits an ultrahigh selectivity and response of over 10.2 and 14.4, respectively, to 50 ppm of H₂S, with a detection limit as low as 3.61 ppb. First-principles density functional theory (DFT) calculations reveal that the enhanced selectivity arose from the molecular sieving effect of ZIF-L, including size exclusion and adsorptive sieving. Furthermore, a flexible ZIF-L/SnS₂ sensor integrated on a polyethylene terephthalate (PET) substrate demonstrates the potential of ZIF-L/TMD heterostructures for wearable applications. This work introduces a novel strategy for improving gas selectivity and advancing the development of high-performance, flexible chemical sensors.