Dual-functional ratiometric fluorescent sensor based on mixed-lanthanide metal-organic frameworks for the detection of trace water and temperature

Rapid-response ratiometric sensors are promising tools to detect trace water and temperature. However, achieving an accurately visualized water assay in a very narrow range is still a challenge. Herein, a novel dual-functional ratiometric luminescent sensor, i.e., Eu2.2Tb97.8-TCA, was successfully fabricated based on lanthanide metal-organic frameworks. This sensor showed a very fast (less than 20 s) and relatively ultrasensitive (limit of detection 0.016% v/v) response to trace water in ethanol, achieving the sensitive visual determination of water in ethanol with multiple readouts. Intriguingly, visual and quantitative determination of water with a detection limit of 0.035% v/v was achieved based on the ratio of green (G) to red (R) values combined with a smartphone color picker application (APP). The mechanism has also been proposed based on experimental and theoretical evaluation. Furthermore, Eu2.2Tb97.8-TCA could monitor temperature in the range of 300 to 380 K with an excellent linear relationship, high accuracy and good recyclability. This material could also be tuned to emit white luminescence and hence can be used as a single-phase UV phosphor. The present work provides a novel Ln-MOF with powerful capabilities to detect trace water and monitor temperature, which paves a way for the rational design and synthesis of multifunctional materials.