MOF-Derived Single and Bimetallic Conductive MOFs for Sensitive NO₂ and H₂S Detection at Room Temperature

While two-dimensional conjugated conductive metal-organic frameworks (2D c-MOFs) are promising for chemiresistive sensing due to their intrinsic porosity and conductivity, their performance is often limited by insufficient active sites and sluggish mass transport inherent to thin-film architectures. To address these challenges, we developed a novel microstructure-conserving transformation strategy to convert insulating MOF precursors into three-dimensional c-MOFs (3D c-MOFs) with enhanced sensing capabilities. A mild wet-chemical method was used to fabricate 3D c-MOFs (CoHHTP, ZnHHTP, and CoZnHHTP) with controlled morphology and composition. The electrical conductivity of these materials was effectively tuned by extending the reaction time. Gas-sensing characterizations reveal that the CoHH-12, ZnHH-24, and CoZnHH-24 sensors exhibit high sensitivity toward nitrogen dioxide (NO₂, 2.7-20 ppm), hydrogen sulfide (H₂S, 3.4-20 ppm), and NO₂ (4.9-20 ppm) at room temperature, respectively. Crucially, the outstanding sensing performance originates from a synergy between the 3D hierarchical porous architecture for rapid gas diffusion and the bimetallic composition for precise electronic modulation. Furthermore, the sensors demonstrate excellent selectivity, repeatability, and stability against interfering gases. This work provides an effective strategy for engineering the morphology and electronic structure of c-MOFs, advancing the development of high-performance room-temperature gas sensors for environmental monitoring.