The modulator 2-fluorobenzoic acid (2-fba) is widely used to prepare RE clusters in metal–organic frameworks (MOFs). In contrast to known RE MOF structures containing hydroxide bridging groups, we report for the first time the possible presence of fluoro bridging groups in RE MOFs. In this report we discuss the synthesis of a holmium-UiO-66 analogue as well as a novel holmium MOF, where evidence of fluorinated clusters is observed. The mechanism of fluorine extraction from 2-fba is discussed as well as the implications that these results have for previously reported RE MOF structures.

Four new isostructural 3d-4f mixed metal organic frameworks (MOFs) Cu Gd2 (BDC)4, compound 1, Cu Ho2 (BDC)4, compound 2, Cu Eu2 (BDC)4, compound 3, and Cu Dy2 (BDC)4, compound 4 were successfully synthesized. The structure, stability, and magnetic properties were analyzed. Each MOF has two lanthanide ions and one copper ion node with terephthalic acid as the organic linker. The lanthanide ions form a dimer with each having a capped trigonal prismatic geometry while the copper ion has a square planar geometry. Each of these MOFs shows varying degrees of antiferromagnetic interactions.