Tunable Chemiresistive Gas Selectivity of Thin-Layered Conductive Metal-Organic Framework/Reduced Graphene Oxide...

Selective and sensitive detection of toxic gases such as hydrogen sulfide (H₂S) at room temperature remains a critical challenge in environmental safety and health monitoring, primarily because strongly oxidative interferences like nitrogen dioxide (NO₂) often dominate the responses of conventional sensors. Herein, we present a precise hybridization strategy that integrates conducting metal-organic frameworks (cMOFs) with reduced graphene oxide (rGO) via layer-by-layer (LBL) assembly of cMOFs on optically reduced GO supports. Among various cMOFs, Cu₃(HITP)₂ (HITP = 2,3,6,7,10,11-hexaimino-triphenylene) was selected to construct rGO@Cu₃(HITP)₂ hybrid composites, in which the number of LBL growth cycles allows systematic control over interfacial thickness and surface chemistry. Notably, the opposite chemiresistive response directions of rGO and Cu₃(HITP)₂ effectively suppress NO₂ sensitivity, whereas H₂S detection is significantly enhanced through preferential chemisorption of sulfur-containing species at the Cu sites, with the rGO matrix providing efficient charge-transport pathways and mechanical stability. The influence of ambient humidity on interfacial charge-transfer pathways was systematically investigated, and humidity-induced selectivity variations were minimized through the integration of a hydrophobic filter. The underlying sensing mechanisms are elucidated through ex situ Raman spectroscopy analysis.