Three new alkaline earth-based metal-organic frameworks based on two tricarboxylic acid ligands: Structural diversity, stability study and luminescent properties

The alkaline earth-based metal-organic frameworks (MOFs) have attracted more and more attention for their beautiful structure and environmental friendliness. In this work, three alkaline earth-based MOFs, namely [Ba(HL1)]n (1), [Ca(HL1)(H2O)2]n (2), and [Ba(HL2)]n (3) (H3L1 = 1-(3-carboxyphenylmethyl)-1H-pyrazol-3,5-dicarboxylic acid and H3L2 = 1-(4-carboxyphenylmethyl)-1H-pyrazol-3,5-dicarboxylic acid), were synthesized under hydrothermal conditions. Compounds 1-3 reveal structural diversity owing to different metal ions and organic ligands. Thermal and solvent stability were characterized by thermogravimetric analyses (TG) and powder X-ray diffraction (PXRD), respectively. The solid-state luminescent properties were also investigated. The result shows a clear correlation between emission bands and excitation wavelengths of compounds 1-3.