Abstract
The red light-emitting [EuW$_{10}$O$_{36}$]$_9$- (EuW$_{10}$) 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-8$^2$. The EuW$_{10}$/GCDs@ZIF-8$^2$ and EuW10/BCDs@ZIF-8$^2$ materials have been characterized by using several techniques, showing their stability and an advantageous low europium content (0.23 wt% for EuW$_{10}$/GCDs@ZIF-8$^2$). 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 EuW$_{10}$/GCDs@ZIF-8$^2$ to behave as a luminescent thermometer with a maximum relative thermal sensitivity of 1.45% degrees C$^{-1}$ at 80°C.