Understanding the effect of charge transfer on the physical properties of metal–organic frameworks (MOFs) is essential for designing multifunctional MOF materials. In this work, three redox-active tetrathiafulvalene (TTF)-based MOFs, formulated as [Co6L6(bpe)6(EtOH)2(MeOH)2(H2O)] n ·5nH2O (1), [Co5(μ3–OH)2L4(bpe)2] n (2), and [CoL­(bpa)­(H2O)] n ·2nH2O (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate, bpe = 1,2-bis­(4-pyridyl)­ethene, bpa = 1,2-bis­(4-pyridyl)­ethane), are crystallographically characterized. Complexes 1 and 3 are two-dimensional (2D) coordination polymers, and 2 features an unusual three-dimensional (3D) MOF. The structure of 2 contains a cluster chain constructed from μ2-O bridged pentanuclear cluster subunits, which is first found for 3D MOFs. Complexes 1 and 2 are comprised of the same ligands L and bpe but with different multidimensional configuration, and complexes 1 and 3 have the same 2D layered structures with the same ligand L but with different conjugation ligand bpe/bpa, which provide a good comparison for the structure–property relationship. The charge-transfer (CT) interactions within MOF 1 are stronger than those of 2 due to the closer packing of electron donor (D) L and electron acceptor (A) bpe in 1, and no CT occurs within MOF 3 because of the unconjugated bpa. The order of photocurrent density is 1 > 2 ≫ 3, which is in accordance with that of CT interactions. Further analysis reveals that the CT interactions within the MOF are not beneficial for the supercapacitance which is verified by the highest supercapacitance performance of 3. This work is the first study of the structures and CT effects on the supercapacitance performance.

Titanium-oxo clusters (TOCs) have been studied for applications in catalysis, energy storage and transfer, light emission, and so on; however, use of TOCs for the selective adsorption of dyes has not yet been reported. Herein, a TOC compound formulated as [Ti6O3(OiPr)14(TTFTC)]4 (1, TTFTC = tetrathiafulvalene-tetracarboxylate) was successfully prepared and crystallographically characterized. Compound 1 has a cyclic structure assembled by four Ti6 clusters and four rodlike TTFTC connectors. Red compound 1 self-condenses to form a black polymeric organic–inorganic hybrid material (denoted as B-1), which was characterized by various techniques. B-1 is an amorphous TiO material that is formed by the irregular condensation of 1 by the removal of alkoxyl groups. B-1 exhibits high dye adsorption efficiency toward cationic dyes with a q e value of 651.3 mg/g at 298 K for methylene blue (MB). Moreover, B-1 can be used to selectively remove MB not only from mixed cationic–anionic dye solutions but also from some mixed cationic dyes, which is related to their structures. Kinetic, isotherm, and thermodynamic studies demonstrated that the pseudo-second-order kinetic model and Freundlich model show a good fit to the experimental data. The adsorption process involves an exothermic and entropy decreasing process. In addition, dye-adsorbed B-1 can be further used as a photocurrent-responsive material. The work opens up a new field for the application of TOCs in the selective adsorption and removal of dyes.

Redox active tetrathiafulvalene (TTF) and its derivatives as electrode additives have exhibited improved energy efficiency and sustainability in batteries. However, the structure–property relationship has not been detailedly investigated until very...