Synthesis and Structure of a Metal-Organic Framework Based on Lanthanum(III) and Diacetylenedibenzoic Acid

Metal-organic frameworks (MOFs) are a widely studied class of compounds characterized by porous structure and large surface area. MOFs are highly promising materials for practical applications as pollution sensors, selective sorbents, etc. There has been increasing recent interest in MOFs containing a long rigid linear linker that can significantly increase the size and area of MOF pores. Derivatives of diacetylenedibenzoic acid can be used as such ligands. In this work, a metal-organic framework based on diacetylenedibenzoic acid and lanthanum is prepared, its single crystals are obtained, and their structure is studied. The synthesis is performed by the solvothermal method using N,N-dimethylformamide (DMF) as a solvent. The structure of the obtained single crystal is determined by single crystal XRD. it is shown that this compound contains a 3D network with stretched (~4×31 Å) orthorhombic channels filled with water and DMF molecules. Lanthanum cations are interconnected into 1D chains by carboxylic groups. The coordination number of lanthanum is eight. Two neighboring La³⁺ ions are connected into linear motifs by the oxygens of carboxylic groups. Each water molecule participates in the formation of hydrogen bonds or in the coordination of La³⁺ ions or in these both interactions. Only half of the DMF molecules have hydrogen bonds; the other half fill MOF pores and form weak van der Waals contacts. Due to the presence of solvent filled pores, this MOF can have a developed surface area.