Synthesis of materials. The materials were prepared with all Ln elements (except for radioactive Pm) and different mixtures of two or more lanthanides. When Ln is Pr or Nd, ethanol were used as solvent, instead of dimethylformamide (in the presence of dimethylformamide the samples contains impurities of Pr or Nd formate). Preparation of the ITQMOF-1-Eu. A solution of EuCl3 (Sigma-Aldrich) in water is mixed with a solution of 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)dibenzoic acid (HFIPBB) (Sigma-Aldrich) in dimethylformamide (DMF) to give the following molar ratio: 2 Eu: 3 HFIPBB: 130 DMF: 190 H2O. The mixture is heated at 423 K in a stainless steel autoclave with a Teflon-liner for 14 hours. After this period the autoclave is slowly cooled down to room temperature and the product is washed several times with DMF and water, filtered and dried at 393 K for 12 hours. The yield of the reaction is 90 %. The product (ITQMOF-1- Eu) is obtained as needle like white crystals with a red fluorescence under UV light. The crystals obtained are insoluble in water and common organic solvents. To liberate the porosity, the powder obtained is heated at 423 K under vacuum at 10 -3 mbar for 3 hours in order to evacuate the solvent adsorbed.