Scandium Metal–Organic Frameworks Containing Tetracarboxylate Linker Molecules: Synthesis, Structural Relationships, and Properties

Abstract

Three structurally related metal–organic frameworks (MOFs) of composition [Sc2(OH)2(L)] denoted Sc-CAU-9-PTCDA, Sc-CAU-9-TCPB, and Sc-CAU-9-H2TCPP containing the tetratopic linker molecules L14– = PTCDA4– (perylene-3,4,9,10-tetracarboxylate), L24– = TCPB4– (1,2,4,5-tetrakis(4-carboxylatophenyl)-benzene), or L34– = H2TCPP4– (meso-tetra(4-carboxylatophenyl)-porphyrin), have been obtained from solvothermal syntheses. The crystal structures were determined from powder X-ray diffraction data. The title compounds contain chains of trans corner-sharing [ScO6] octahedra, connected by the linker molecules to form three-dimensional networks. Depending on the shape of the respective linker the compounds crystallize in a frz or fry topology and with increasing size of the linker, an expansion of the framework and the formation of accessible channels are observed. The compounds were thoroughly characterized and exhibit high thermal stabilities up to 500 °C. Sc-CAU-9-TCPB and Sc-CAU-9-H2TCPP possess permanent porosity toward nitrogen with specific surface areas of asBET = 1350 m2/g and 650 m2/g, respectively. Luminescence measurements revealed a ligand-based emission in the blue spectral region for Sc-CAU-9-TCPB.