Synthesis, Characterization, and Luminescence Modulation of a Metal-Organic Framework Based on a Cyclotriphosphazene-Functionalized Multicarboxylate Ligand.

Abstract

By using a multicarboxylate ligand consisting of six peripheral 1,3-benzenedicarboxylalte units connected to the central cyclotriphosphazene ring through a P-O-C spacer, a novel metal-organic framework, [Cd5 L(H2 O)4 ]⋅2 (CH3 )2 NH2 ⋅6 DMF (L=hexakis(3,5-dicarboxylatephenyloxy)cyclotriphosphazene), was solvothermally synthesized and characterized by single-crystal and powder XRD, thermal gravimetric analysis, and IR and photoluminescence spectroscopy. Single-crystal XRD analyses show that the framework is an anionic 3D network assembled from pentanuclear [Cd5 (COO)10 ] secondary building units and organic linkers. TOPOS software analyses indicate that two alternative simplifications based on the organic linkers can produce five-connected uninodal bnn-type topology or novel (2,3,6,10)-connected five-nodal topology. Additionally, it is interesting that the luminescence intensity of the complex can be modulated by postsynthetic ion exchange. This study highlights that cyclotriphosphazene-functionalized multicarboxylates, with the combined advantages of conformation diversity and easy functionalization, are a promising type of organic ligand for the synthesis of metal-organic frameworks with fascinating structures and interesting properties.