Solvent induced structural transformation of a cerium(iii) 2,5-furandicarboxylate metal–organic framework

Abstract

The synthesis and structural characterisation of a cerium(III) MOF, UOW-11, is reported. The material is constructed using the sustainably sourced 2,5-furandicarboxylate (FDC) linker under solvothermal conditions in N,N-dimethylformamide (DMF) solvent and scalable to gram-scale production. Single-crystal analysis using 3D electron diffraction reveals a unique framework architecture, P2₁/n space group, with composition [Ce₄(FDC)₇(DMF)_2.36](DMA)₂ that has a structure containing four cerium(III) sites that are connected via bridging FDC ligands to give a 3D extended anionic framework counterbalanced by occluded dimethylammonium (DMA) cations, formed via partial decomposition of DMF. Upon exposure to water, UOW-11 undergoes a structural transformation, forming a second, structurally distinct Ce(III) coordination polymer, [Ce₂(FDC)₂(H₂O)₁₀]FDC·6H₂O, UOW-2(Ce), which crystallises in the triclinic space group P. The asymmetric unit comprises two Ce³⁺ ions, coordinated by two FDC²⁻ ligands, ten water molecules, with one additional uncoordinated FDC²⁻ ligand, and six occluded water molecules. The transformation leads to significant changes in coordination geometry and composition, including the loss of DMA and a different Ce : FDC ratio, consistent with a dissolution–recrystallisation mechanism. Monitoring the conversion using in situ infra-red spectroscopy shows the transformation is complete after ∼3 hours at room temperature.