Two-dimensional Cu(I)-MOF with mesoporous architecture towards chemiresistive NO2 sensing

Abstract

Conducting metal-organic frameworks (c-MOFs) have emerged as a promising platform for chemiresistive gas sensors due to their intrinsic porosity and ability to facilitate charge transfer upon gas adsorption. In this study, we report a semiconducting copper(I)-MOF (Cu-MOF) formed by the self-assembly of CuI and N-phenyl-N-(pyridin-4-yl)pyridin-4-amine (PDPA). The Cu-MOF consists of a 2D network comprising Cu4I4 secondary building units, which forms an intercalating 3D structure driven by multiple weak interactions. The semiconducting nature and mesoporous structure motivated the exploration of its chemiresistive gas sensing capabilities. The chemiresistive device fabricated with Cu-MOF displays high selectivity and efficient room temperature NO₂ sensing with a lower limit of detection (3.5 ppb) and a swift response/recovery times (~11/13s), the fastest among the reported state-of-the-art MOF-based NO2 sensors. Experimental and theoretical analysis reveals that the adsorption of NO₂ on Cu-MOF withdraws electrons from the Cu(I) center, leading to a change in electrical response. The rapid response/recovery without any external stimuli, repeatability and material robustness further enhance its potential applications.