Template-Directed Synthesis of MOF-Based Sensors for Ultratrace Gas Sensing

Conductive metal-organic frameworks (c-MOFs) offer great promise for sensing applications, yet the controlled fabrication of c-MOF thin films with defined morphology, thickness, and even orientation remains a significant challenge. Herein, we describe a template-directed strategy to enable the in-situ growth of a series of c-MOFs on polypyrrole@graphene oxide (PPy@GO) nanosheets with variable morphologies and texture. Leveraging the abundant surface functional groups and 2D topological structure of PPy@GO nanosheets, controlled self‑assembly of Ni₃(HHTP)₂ on their surface is achieved. The growth of Ni₃(HHTP)₂ on the PPy@GO templates proceeds via a Volmer-Weber growth mode. The resulting PPy@GO/Ni₃(HHTP)₂ based sensors with good conductivity and enhanced porosity exhibit sensitive and selective detection toward NO₂ at room temperature with a detection limit of 350 ppb, outstanding compared to the previously reported NO₂ sensors. This excellent NO₂ sensing performance can be attributed to the efficient charge transfer between the adsorbed NO₂ molecules and PPy@GO/Ni₃(HHTP)₂ verified by multiple characterizations. This work offers a novel strategy for preparing gas-sensitive materials with salient sensing performance toward practical applications.