Influence of synthesis time on the microstructure and photophysical properties of Gd-MOFs doped with Eu 3þ Jarley Fagner Silva do Nascimento a, d , Br  aulio Silva Barros a, b, * , Joanna Kulesza c , Jo ~ ao Bosco Lucena de Oliveira a , Ana Karina Pereira Leite a , Rosiv ^ ania Silva de Oliveira a a Federal University of Rio Grande do Norte, Institute of Chemistry, PO Box 1662, 59078-970, Natal, RN, Brazil b Federal University of Pernambuco, Department of Mechanical Engineering, 50070-901, Recife, PE, Brazil c Federal University of Pernambuco, Department of Fundamental Chemistry, 50070-901, Recife, PE, Brazil d Federal Institute of Education, Science and Technology of the Rio Grande do Norte, 59500-000, Macau, RN, Brazil highlights graphical abstract  Red-luminescent Eu/Gd-1,4BDC MOFs were obtained by sol- vothermal method.  Efficient antenna effect was observed.  PL properties were morphology dependent. article info Article history: Received 12 October 2016 Received in revised form 23 December 2016 Accepted 8 January 2017 Available online 9 January 2017 Keywords: MOFs Lanthanides Antenna effect Photoluminescence Microstructure 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 Eu 3þ were synthesized via solvothermal method at 180  C. The effect of the synthesis time (3, 5 or 7 days) on the microstructure and photophysical prop- erties 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 photo- luminescence excitation and emission spectra revealed an efficient energy transfer from the ligand to the Eu 3þ levels (antenna effect), what is not expected for 1,4-BDC 2- in a Eu(III)-based MOFs. We concluded that the presence of highly paramagnetic Gd 3þ ions in the matrix enhanced the antenna effect, resulting in a strong red emission. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Metal-organic frameworks (MOFs) comprise a broad class of crystalline materials defined as porous networks consisting of metallic ions or clusters linked together by organic multidentate * Corresponding author. Federal University of Pernambuco, Department of Me- chanical Engineering, Av. Prof. Moraes Rego-1235 e Cidade Universit aria, 50070- 901, Recife, PE, Brazil. E-mail address: braulio.barros@ufpe.br (B.S. Barros). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys http://dx.doi.org/10.1016/j.matchemphys.2017.01.024 0254-0584/© 2017 Elsevier B.V. All rights reserved. Materials Chemistry and Physics 190 (2017) 166e174