Solution‐Processable MOF‐on‐MOF System Constructed via Template‐Assisted Growth for Ultratrace H2S Detection

Conductive metal–organic frameworks (c‐MOFs) hold promise for highly sensitive sensing systems due to their conductivity and porosity. However, the fabrication of c‐MOF thin films with controllable morphology, thickness, and preferential orientation remains a formidable yet ubiquitous challenge. Herein, we propose an innovative template‐assisted strategy for constructing MOF‐on‐MOF (Ni3(HITP)2/NUS‐8 (HITP: 2,3,6,7,10,11‐hexamino‐tri (p‐phenylene))) systems with good electrical conductivity, porosity, and solution processability. Leveraging the 2D nature and solution processability of NUS‐8, we achieve the controllable self‐assembly of Ni3(HITP)2 on NUS‐8 nanosheets, producing solution‐processable Ni3(HITP)2/NUS‐8 nanosheets with a film conductivity of 1.55×10−3 S ⋅ cm−1 at room temperature. Notably, the excellent solution processability facilitates the fabrication of large‐area thin films and printing of intricate patterns with good uniformity, and the Ni3(HITP)2/NUS‐8‐based system can monitor finger bending. Gas sensors based on Ni3(HITP)2/NUS‐8 exhibit high sensitivity (LOD~6 ppb) and selectivity towards ultratrace H2S at room temperature, attributed to the coupling between Ni3(HITP)2 and NUS‐8 and the redox reaction with H2S. This approach not only unlocks the potential of stacking different MOF layers in a sequence to generate functionalities that cannot be achieved by a single MOF, but also provides novel avenues for the scalable integration of MOFs in miniaturized devices with salient sensing performance. The stable Ni3(HITP)2/NUS‐8 systems, synthesized via an innovative template‐assisted approach, display high conductivity, porosity, and solution processability. Gas sensors utilizing these systems demonstrate significant sensitivity to ultratrace H2S at room temperature and outstanding selectivity. Additionally, wearable sensors integrating these systems can capture human motion signals, opening up new possibilities for such devices.