Solvato/Vapochromism‐Based Alcohol Sensing through Metal–Organic Framework Thin Films with Coordinatively Unsaturated Metal Sites

Ethanol (EtOH) is a ubiquitous compound with critical applications across various industries, necessitating accurate and reliable sensing for sanitation, quality control, and environmental monitoring. Chromism-based sensors, known for their simplicity, portability, and real-time detection capabilities, have faced limitations in EtOH sensing due to insufficient sensitivity, low selectivity, irreversibility, and low color perception. Herein, a groundbreaking solvato/vapochromism-based EtOH sensor utilizing a Cu-based metal-organic framework (MOF) thin film, Cu-MOF-74, is reported. The conversion of Cu-based ceramics to Cu-MOF-74 facilitates the fabrication of solvato/vapochromic MOF thin films with low light scattering, enabling effective colorimetric analysis. The Cu-MOF-74 thin films demonstrate rapid and reversible solvato/vapochromism upon the adsorption of guest molecules, including water and EtOH. This unique behavior allows for the precise and reliable detection of EtOH across the entire concentration range. Furthermore, a smartphone application is developed to detect EtOH concentrations, enabling rapid and convenient evaluation of EtOH levels. The findings represent a significant advancement in EtOH sensing technology, overcoming the limitations of traditional methods. The Cu-MOF-74-based sensor offers a versatile and reliable solution for various applications, including environmental monitoring, process control, and healthcare.