Two solvent-stable MOFs as a recyclable luminescent probe for detecting dichromate or chromate anions

Abstract

Two unique 2D Zn-MOFs with the formulas {[Zn(btz)]_n} (1) and {[Zn₂(ttz)H₂O]_n} (2) were synthesized using in situ generated ligands under hydro(solvo)thermal conditions. Both 1 and 2 exhibit high thermo-stability, solvent-stability and pH-stability. Thermogravimetric analyses (TGA) reveal that 1 and 2 remain intact until about 365 °C and 332 °C, respectively. The samples of 1 and 2 were immersed in twelve common solvents for 24 hours, and the obtained PXRD patterns remain well consistent with the simulated ones. They were immersed in a series of solutions with pH values ranging from 1.0 to 14.0 for five hours, and the PXRD patterns of these samples remain unchanged spanning the pH range of 1–13. The luminescence investigations reveal that the compounds 1 and 2 can efficiently and selectively detect Cr₂O₇²⁻ or CrO₄²⁻ among twenty-one anions. Importantly, they can be regenerated by a fast and simple method in detecting Cr₂O₇²⁻ or CrO₄²⁻.