Metal–Organic Framework Flowers as a Naked-Eye Colorimetric Indicator of Trace Water

Abstract

Convenient and sensitive trace water indication is of great significance in various industrial processes. Here, a flower-like metal–organic framework Cu-FMM is assembled from ultrathin nanosheets that change its coordination structure reversibly with the capture and loss of water molecules, enabling sensitive trace water naked-eye colorimetric indication ability. A recognizable black/yellow color change can be observed when the dried Cu-FMM is exposed to the atmosphere or solvent with trace water as low as RH 3% and a water content of 0.25‰ (v/v) and further enables potential trace water imaging applications. The excellent accessibility of the multi-scale pore structure of Cu-FMM contributes to a fast response time of 3.8 s with good reversibility (>100 cycles), outperforming traditional coordination polymer humidity sensors. The present study provides new inspirations for the design of sensitive and applicable naked-eye water indicator materials that are applicable to in situ and continuous monitoring in industrial processes.

Smartphone Imaging Device for Multimodal Detection of Hydrogen Sulfide Using Cu-Doped MOF Sensors

“…These methods undergo inevitable issues, such as requirements of sophisticated pretreatments, high cost, time-consuming manipulations, professional technicians, and poor analytic specificity and accuracy. To solve these issues, it is required to construct robust, fast, and efficient analytic platforms for accurate determination of H 2 S. Colorimetric analysis is fast, simple, low-cost, and on-the-spot, − while the electrochemical sensing platform is ultrasensitive and has great adaptability for H 2 S determination. , Notably, the colorimetric-based sensing platform possesses a significant color change, which can achieve the naked-eye readout for semiquantitative analysis . Despite the advanced effort in the rational design of the H 2 S sensing platform, the single signal output can still generate unstable and false results. − Integrating multiple signal analysis, which complements the merits of each sensing platform through different detection mechanisms, can obviously boost accuracy and reliability for H 2 S determination.…”