Two new Cd-based metal–organic frameworks for afterglow detection of Fe3+ and NH3

Abstract

Luminescent metal–organic frameworks (LMOFs) have been extensively employed as detection probes. However, the majority of the reported probes are fluorescence-based, lacking reports on visible afterglow detection. Herein, we present two new afterglow MOFs, compound 1 with a layered structure and 2 with an interpenetrated dia framework. 1 exhibits blue-green room temperature phosphorescence (RTP) (τ_485nm = 264.6 ms) and can serve as an afterglow “turn off” probe for selective detection of Fe³⁺ ions through a framework decomposition mechanism, with a detection limit of 1.63 μM. Displaying blue-green RTP (τ_495nm = 83.0 μs), 2 can serve as an afterglow “turn on” probe for the detection of NH₃ in both solution and vapor phases. Notably, the afterglow of 2 is visually activated even at concentrations of NH₃ vapor as low as 6 ppm. Mechanistic investigations reveal that the “turn on” response is attributed to structural transformation induced by NH₃ molecules replacing coordinated solvents. Furthermore, their potential applications were demonstrated through the development of portable test strips for detecting Fe³⁺ ions and an cryptographic algorithm logic gate for NH₃ deciphering. This work opens up new opportunities for the development of LMOF-based afterglow probes.