Different two-dimensional metal-organic frameworks through ligand modification

<p>Through ligand modification, we have replaced the central benzene ring of H<sub>2</sub>TDBA ([1,1′:3′,1″-terphenyl]-4,4″-dicarboxylic acid) with the pyridine structurally related ligand H<sub>2</sub>PDDA (4,4′-(pyridine-2,6-diyl)dibenzoic acid), which makes the central pyridine ring of H<sub>2</sub>PDDA more coplanar with two benzene rings on both sides of the ligand. The modification results in a dramatically different linkage configuration, thereby allowing structural changes to the metal-organic frameworks (MOFs). Two 2-D MOFs, [Cu(TDBA)(DMA)<sub>2</sub>]·H<sub>2</sub>O (<b>BUT-221</b>, DMA = <i>N</i>,<i>N</i>-dimethylacetamide), and [Cu<sub>3</sub>(PDDA)<sub>3</sub>(DMA)<sub>2</sub>(H<sub>2</sub>O)]·5H<sub>2</sub>O (<b>BUT-223</b>) have been synthesized through reactions of two ditopic carboxylate ligands with Cu(NO<sub>3</sub>)<sub>2</sub>·3H<sub>2</sub>O under solvothermal conditions, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. Topological analysis shows that <b>BUT-221</b> is a twofold parallel interpenetrating 4<sup>4</sup> 2-D network with a <i>skl</i> topology, while <b>BUT-223</b> is a 2-D network with a <i>kgm</i> topology.</p>