Synthesis, Structure, and Luminescent Properties of Microporous Lanthanide Metal−Organic Frameworks with Inorganic Rod-Shaped Building Units

A series of microporous lanthanide metal−organic frameworks, Tb3(BDC)4.5(DMF)2(H2O)3·(DMF)(H2O) (1) and Ln3(BDC)4.5(DMF)2(H2O)3·(DMF)(C2H5OH)0.5(H2O)0.5 [Ln = Dy (2), Ho (3), Er (4)], have been synthesized by the reaction
of the lanthanide metal ion (Ln3+) with 1,4-benzenedicarboxylic acid and triethylenetetramine in a mixed solution of
N,N‘-dimethylformamide (DMF), water, and C2H5OH. X-ray diffraction analyses reveal that they are extremely similar
in structure and crystallized in triclinic space group P1̄. An edge-sharing metallic dimer and 4 metallic monomers
assemble with 18 carboxylate groups to form discrete inorganic rod-shaped building units [Ln6(CO2)18], which link
to each other through phenyl groups to lead to three-dimensional open frameworks with approximately 4 × 6 Å
rhombic channels along the [0,−1,1] direction. A water sorption isotherm proves that guest molecules in the framework
of complex 1 can be removed to create permanent microporosity and about four water molecules per formula unit
can be adsorbed into the micropores. These complexes exhibit blue fluorescence, and complex 1 shows a Tb3+
characteristic emission in the range of 450−650 nm.