Homoleptic imidazolate frameworks 3∞[Sr1−xEux(Im)2]—hybrid materials with efficient and tuneable luminescence

Abstract

Homoleptic frameworks of the formula ³_∞[Sr_1−xEu_x(Im)₂] (1) (x = 0.01–1.0; Im⁻ = imidazolate anion, C₃H₃N₂⁻) are hybrid materials that exhibit an intensive green luminescence. Tuning of both emission wavelength and quantum yield is achieved by europium/strontium substitution so that a QE of 80% is reached at a Eu content of 5%. Even 100% pure europium imidazolate still shows 60% absolute quantum efficiency. Substitution of Sr/Eu shows that doping with metal cations can also be utilized for coordination compounds to optimize materials properties. The emission is finely tuneable in the region 495–508 nm via variation of the europium content. The series of frameworks ³_∞[Sr_1−xEu_x(Im)₂] presents dense MOFs with the highest quantum yields reported for MOFs so far.