Solvent-Dependent Formation of Three New Bi-Metal–Organic Frameworks Using a Tetracarboxylic Acid

Systematic solvent screening using high-throughput solvothermal syntheses with bismuth nitrate pentahydrate and 1,2,4,5-tetrakis-(4-carboxyphenyl)­benzene (H₄TCPB) led to three new porous Bi-metal–organic frameworks [Bi₂(H₂TCPB)­(TCPB)­(H₂O)₂]­·xH₂O (CAU-31), (NH₂(CH₃)₂)­[Bi­(TCPB)­(H₂O)]­·xH₂O (CAU-32), and [Bi₄(O)₂­(OH)₂­(H₂TCPB)­(TCPB)­(H₂O)₂]­·xH₂O (CAU-33). Compounds CAU-31, -32, and -33 were synthesized in CH₃OH, CH₃OH/DMF, and DMF/toluene, respectively. The crystal structures were determined using electron diffraction and single-crystal X-ray diffraction in combination with the Rietveld method. The structures of CAU-31 and CAU-32 are composed of isolated Bi³⁺ ions as the inorganic building unit (IBU), which are connected by the linker ions to form a layered structure with inclined interpenetration and a three-dimensional anionic network, respectively. The IBU of CAU-33 consists of infinite bismuth-oxo rods forming a three-dimensional network by connection of the organic linkers. For CAU-33 structural flexibility was observed, and two phases denoted α- and β-CAU-33 could be isolated.