Fabrication of lanthanide complexes in metal-organic frameworks as self-calibrating temperature sensor

Temperature plays an important role as a physical parameter in industry and science, it is crucial to measure temperature accurately. Herein, by “ship-in-a-bottle” strategy, Ln(phen) (Ln = Eu³⁺, Tb³⁺; phen = 1,10-phenanthroline) was successfully prepared in one-dimensional pores of Na–Zn-MOF. With the lanthanide co-doping approach, Eu_xTb_1-x(phen)@Na–Zn-MOF (3–7@Na–Zn-MOF) were achieved. The luminescent properties of Eu_xTb_1-x(phen)@Na–Zn-MOF revealed systematic tuning of their luminescent colors from green, through yellow to red with increasing Eu³⁺ doping concentration. Interestingly, two fluorescence emission peaks of 5@Na–Zn-MOF at 544 nm and 617 nm demonstrate different fluorescence responses to temperature, exhibiting self-calibrating sensor in the range of 293–373 K with the supreme relative sensitivity of 11.02 %·K⁻¹ at 373 K. Moreover, its luminescent color changes from yellow (293 K) to red (373 K), representing suitable as colorimetric luminescent sensor. Furthermore, 5@Na–Zn-MOF was blended with poly(vinylidene fluoride) (PVDF) to produce a mixed-matrix membrane (MMM), which also shows excellent temperature response accompanied by color changing.