Tunable ratiometric temperature sensors based on a Zn-MOF material incorporating luminescent polyoxometalates and carbon dots

Abstract

The red light-emitting [EuW₁₀O₃₆]⁹⁻ (EuW₁₀) polyoxometalate (POM) and carbon dots (CDs) with green (GCDs) or blue (BCDs) luminescence have been co-immobilized in the hierarchically porous metal–organic framework (MOF) ZIF-8². The EuW₁₀/GCDs@ZIF-8² and EuW₁₀/BCDs@ZIF-8² materials have been characterized by using several techniques, showing their stability and an advantageous low europium content (0.23 wt% for EuW₁₀/GCDs@ZIF-8²). In addition, theoretical calculations were performed in order to localize the POM units into the composite, considering two types of environments. In-depth investigations of their optical properties in the solid state show significant differences between both composites, demonstrating the versatility of POMs/CDs based materials. Moreover, they reveal the ability of EuW₁₀/GCDs@ZIF-8² to behave as a luminescent thermometer with a maximum relative thermal sensitivity of 1.45% °C⁻¹ at 80 °C.