Topotactic Conversion of Titanium-Oxo Clusters to a Stable TOC-Based Metal-Organic Framework with the Selective Adsorption of Cationic Dyes.

Titanium-oxo cluster (TOC)-based metal-organic frameworks (MOFs) have received considerable attention in recent years due to their ability to expand the application of TOCs to fields that require highly stable frameworks. Herein, a new cyclic TOC formulated as [TiO(OPr)(TTFTC)(phen)] (, where TTFTC = tetrathiafulvalene tetracarboxylate and phen = phenanthroline) was crystallographically characterized. TOC takes a rectangular ring structure with two phen-modified Ti clusters as the width and two TTFTC ligands as the length. An intracluster ligand-to-ligand (TTF-to-phen) charge transfer in was found for TOCs for the first time. Compound undergoes topotactic conversion to generate stable TOC-MOF , in which the rectangular framework in formed by a TOC core and ligands is retained, as verified by comprehensive characterization. shows an efficient and rapid selective adsorption capacity for cationic dyes. The experimental adsorption capacity () of reaches a value of up to 789.2 mg/g at 298 K for the crystal violet dye, which is the highest among those of various adsorbents. The calculated models are first used to reveal the structure-property relationship of the cyclic host to different guest dyes. The results further confirmed the host MOF structure of .