Influence of the synthesis time on the microsstructure and photophysical properties of Gd-MOFs doped with Eu3+

Abstract

Metal Organic Frameworks (MOFs) are hybrid materials, usually crystalline, consisting of metallic species or clusters, connected by polytopic organic ligands originating bi or tridimensional porous structures. In this work, Gd-1,4-BDC-MOFs doped with 5% mol Eu3+ were synthesized via solvothermal method at 180°C. The effect of the synthesis time (3, 5 or 7 days) on the microstructure and photophysical properties of the obtained MOFs were evaluated. It was found that porous agglomerates were formed within three days, gradually changing their morphology to rod-like crystals within seven days. The photoluminescence excitation and emission spectra revealed an efficient energy transfer from the ligand to the Eu3+ levels (antenna effect), what is not expected for 1,4-BDC2- in a Eu(III)-based MOFs. We concluded that the presence of highly paramagnetic Gd3+ ions in the matrix enhanced the antenna effect, resulting in a strong red emission.