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

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.