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.

Supramolecular/macromolecular organic radical contrast agents (smORCAs) overcome many of the limitations of nitroxide radicals for use in magnetic resonance imaging in vivo like poor stability and weak contrast.

A new fluoro-bridged rare-earth (RE) metal−organic framework consisting of 15-connected nonanuclear and 9-connected trinuclear clusters {[RE 9 -(μ 3 -F) 14 (H 2 O) 6 ][RE 3 (μ 3 -F)(H 2 O) 3 ](HCO 2 ) 3 -(BTB) 6 }•(solvent)x 2 (RE = Ho 3+ and Gd 3+ ) was synthesized through the transformation of a dimeric complex formulated as bis(2,2′-bipyridine)tetrakis(μ-2-fluorobenzoato-O,O′)-bis(2fluorobenzoato)diRE(III) 1 with the bridging linker 1,3,5-tris(4-carboxyphenyl)benzene (H 3 BTB). The rare-earth metal ions Ho 3+ and Gd 3+ were also found to remove fluorine from other organo-fluorine compounds such as perfluorohexanoic acid (PFHxA) and perfluorooctanoic acid (PFOA), resulting in the new fluorobridged RE-MOFs.