Synthesis, structure, and fluorescence properties of a calcium-based metal–organic framework

The solvothermal reaction of a mixture of calcium acetylacetonate and 1,4-naphthalenedicarboxylic acid (H(2)NDC) in a solution containing ethanol and distilled water gave rise to a metal–organic framework (MOF), {(H(3)O(+))(2)[Ca(NDC)(C(2)H(5)O)(OH)]}(4)·1.1H(2)O. This MOF possesses a new structure composed of calcium clusters and H(2)NDC linker anions and shows a unique fluorescence property; it exhibits a fluorescence peak at 395 nm (λ(ex) = 350 nm) at room temperature, which is blue-shifted compared with that exhibited by the free H(2)NDC ligand. One of the possible mechanisms for this fluorescence is likely attributable to a ligand-to-metal charge transfer (LMCT) transition and is the first example of a calcium-based MOF exhibiting blue-shifted fluorescence due to LMCT.