Ligand-Responsive MOF-Based Colourimetric Sensor for Visual Identification of Colourless Corrosive Acid and Base Vapours

Abstract

The development of reliable sensors for identifying corrosive vapours remains a significant challenge due to the high reactivity of these vapours and the fundamentally distinct sensing mechanisms required for acids and bases. Herein, we report a single-component colourimetric sensor based on Cu2+-functionalised MOF-808 (Cu-MOF-808) capable of visually distinguishing six representative corrosive vapours, including hydrogen halides (HCl, HBr, HI) and volatile amines (NH3, ethylenediamine, N2H4). Cu2+ ions were post-synthetically anchored onto the Zr6 nodes of the robust MOF-808 framework, providing accessible and reactive sites for vapour-responsive colour changes. The sensor exhibited distinct, analyte-specific colour transitions upon vapour exposure while remaining stable under variations in humidity, temperature, and common interfering gases. For practical application, Cu-MOF-808 was embedded in a flexible PVDF matrix to fabricate a portable sensor film. Upon vapour exposure, colour changes were digitised into RGB values and accurately classified within 15 seconds via statistical analysis. These results highlight the potential of Cu-MOF-808 as a practical sensor for real-time monitoring of corrosive gases in the real-world.