1983494 Eu-MOF europium metal-organic framework 38 1983489 Eu-MOF europium-organic framework 2 1983492 Eu-MOF Eu(III)-organic framework 1 1983491 Eu-MOF Eu-based Metal-Organic Framework sensor 1 1983490 Eu-MOF europium-based framework 1 1983493 Eu-MOF europium-based MOF 1