Bimetallic Conductive Co/Fe‐HITP for Sensitive H 2 S Detection at Low Temperature

The metal nodes in conductive metal‐organic (c‐MOFs) play a crucial role in determining surface chemical activity. Tuning the metal sites of Co 3 (HITP) 2 is expected to enhance its low‐temperature gas sensing performance. Here, a series of bimetallic Co/Fe‐HITP materials are synthesized by partially substituting Co with Fe ions at varying Fe/Co ratios. Gas sensing tests reveal that the Fe incorporation not only improves the response of H 2 S at low temperature but also reduces the fluctuations caused by low temperatures. The optimal Co 1.5 Fe 1.5 ‐HITP 9.5 sensor delivers a response of 10.05 toward 20 ppm H 2 S at room temperature (25°C) and 9.69 at a refrigerating temperature (0°C), with corresponding LODs of 18.9 ppb and 16.8 ppb, respectively. Density functional theory (DFT) calculations on Co‐HITP, Co 2 Fe 1 ‐HITP 9.5 , and Co 1 Fe 2 ‐HITP 9.5 show that increasing the Fe content leads to a larger absolute adsorption energy, rationalizing the enhanced low‐temperature sensing performance. Furthermore, band structure analysis elucidates the origin of the higher surface catalytic activity upon Fe substitution. This work establishes bimetallic Co/Fe‐HITP as a promising platform for sensitive, low‐temperature H 2 S detection.