Solution‐Processable MOF‐on‐MOF System Constructed via Template‐Assisted Growth for Ultratrace H 2 S Detection

Abstract 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 (Ni 3 (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 Ni 3 (HITP) 2 on NUS‐8 nanosheets, producing solution‐processable Ni 3 (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 Ni 3 (HITP) 2 /NUS‐8‐based system can monitor finger bending. Gas sensors based on Ni 3 (HITP) 2 /NUS‐8 exhibit high sensitivity (LOD~6 ppb) and selectivity towards ultratrace H 2 S at room temperature, attributed to the coupling between Ni 3 (HITP) 2 and NUS‐8 and the redox reaction with H 2 S. 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.