A Highly Chemically Stable Metal-Organic Framework as a Luminescent Probe for the Regenerable Ratiometric Sensing of pH

A heteroatom-rich 3D noninterpenetrating metal-organic framework (MOF) Cd-EDDA constructed from an ethylene glycol ether bridging tetracarboxylate ligand H4 EDDA (5,5'-(ethane-1,2-diylbis(oxy))diisophthalic acid) shows good chemical resistance to both acidic and alkaline solutions with a pH ranging from 2.0 to 12.2. There is a corresponding ratiometric luminescence response to pH from 2.0 to 11.5, and the sensing mechanism is also discussed through ion chromatography and molecular force field-based calculations. Importantly, the probe can easily be regenerated simply by modulating the pH of the solution, thus being the first example of a regenerable MOF-based ratiometric luminescent probe for pH.