Characterization of a Holmium 4,4′-Biphenyldicarboxylate Metal-Organic Framework and Its Potential as a Holmium Carrier System

Abstract

There is growing interest in Holmium carriers for radiotherapeutic applications. In this work, a holmium-based metal-organic framework (MOF) using the 4,4′-biphenyldicarboxylic acid (H2BPDC) linker was synthesized and characterized to explore its potential as a radiotherapeutic carrier. The 3D MOF [Ho(BPDC)2]·(CH3)2NH2 was characterized by single crystal X-ray diffraction, FTIR, TGA and PXRD. A challenge to overcome in lanthanide-based MOFs is the deformation or collapse of the framework that can occur after evacuation of the pores. This structure displays high thermal stability and no collapse was observed when the molecules confined in the pores were removed. The coordination around the holmium center (CN = 8) is the key to this stability since only the organic linker and no solvent molecules coordinate to the metallic center. The porosity of the material was confirmed by high-pressure carbon dioxide (CO2) adsorption–desorption analysis. The stability of the MOF, its holmium content (28 wt%) and its porosity are features that make this material a potential holmium carrier for radiotherapeutic applications.

Fluorine extraction from organofluorine molecules to make fluorinated clusters in yttrium MOFs

“…[20][21][22][23][24][25] The RE metal ions tend to form dimers that oen result in MOFs with low porosity. [26][27][28] It has been widely reported that the addition of a modulator can result in RE-MOFs with larger metal clusters. [29][30][31][32] Modulators were originally designed to bind to metal ions to control crystallization rates, oen leading to larger X-ray quality crystals.…”

Fluoro-Bridged Clusters in Rare-Earth Metal–Organic Frameworks

“…We have previously synthesized holmium-based MOFs (Ho-MOFs), in part because holmium can be neutron activated and used for radiotherapy. − Generally, using benzene dicarboxylate (BDC) or related linkers resulted in MOFs only containing Ho 3+ dimers. Therefore, we tested 2-fba as a modulator, since the reported clusters in these MOFs impart better stabilities.…”

Fluoro-bridged rare-earth metal–organic frameworks

“…Smaller metal nodes tend to form non-porous 2D and 3D coordination polymers. [23][24][25][26] However, some RE-MOFs with smaller metal nodes also exhibit porous frameworks such as RE-MOF-76 [RE(btc), btc = benzene-1,3,5-tricarboxylat] and MIL-103 [RE(btb)(H 2 O), btb = 1,3,5-benzenetrisbenzoate]. [27][28][29] The introduction of modulators including organofluorine molecules has resulted in hexanuclear clusters, similar to the hexacluster nodes in Zr-UiO-66, [Zr 6 O 4 (OH) 4 (bdc) 6 , bdc = benzene-1,4-dicarboxylat].…”