An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Poor electrical conductivity and instability of metal–organic frameworks (MOFs) have limited their energy storage and conversion efficiency. In this work, we report the application of oxidatively doped tetrathiafulvalene (TTF)-based MOFs for high-performance electrodes in supercapatteries. Two isostructural MOFs, formulated as [M(py-TTF-py)(BPDC)]·2H2O (M = NiII (1), ZnII (2); py-TTF-py = 2,6-bis(4′-pyridyl)TTF; H2BPDC = biphenyl-4,4′-dicarboxylic acid), are crystallographically characterized. The structural analyses show that the two MOFs possess a three-dimensional 8-fold interpenetrating diamond-like topology, which is the first example for TTF-based dual-ligand MOFs. Upon iodine treatment, MOFs 1 and 2 are converted into oxidatively doped 1-ox and 2-ox with high crystallinity. The electrical conductivity of 1-ox and 2-ox is significantly increased by six∼seven orders of magnitude. Benefiting from the unique structure and the pronounced development of electrical conductivity, the specific capacities reach 833.2 and 828.3 C g–1 at a specific current of 1 A g–1 for 1-ox and 2-ox, respectively. When used as a battery-type positrode to assemble a supercapattery, the AC∥1-ox and AC∥2-ox (AC = activated carbon) present an energy density of 90.3 and 83.0 Wh kg–1 at a power density of 1.18 kW kg–1 and great cycling stability with 82% of original capacity and 92% columbic efficiency retention after 10,000 cycles. Ex situ characterization illustrates the ligand-dominated mechanism in the charge/discharge processes. The excellent electrochemical performances of 1-ox and 2-ox are rarely reported for supercapatteries, illustrating that the construction of unique highly dense and robust structures of MOFs followed by postsynthetic oxidative doping is an effective approach to fabricate MOF-based electrode materials.
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 [Ti6O6(OiPr)8(TTFTC)(phen)2]2 (1, where TTFTC = tetrathiafulvalene tetracarboxylate and phen = phenanthroline) was crystallographically characterized. TOC 1 takes a rectangular ring structure with two phen-modified Ti6 clusters as the width and two TTFTC ligands as the length. An intracluster ligand-to-ligand (TTF-to-phen) charge transfer in 1 was found for TOCs for the first time. Compound 1 undergoes topotactic conversion to generate stable TOC-MOF P1, in which the rectangular framework in 1 formed by a TOC core and ligands is retained, as verified by comprehensive characterization. P1 shows an efficient and rapid selective adsorption capacity for cationic dyes. The experimental adsorption capacity (qex) of P1 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 P1.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Metal–organic frameworks (MOFs) have been found to be promising electrode materials for hybrid lithium-ion capacitors (HLICs) but face challenges due to their low capacity and cycling instability. Here, the first tetrathiafulvalene (TTF)-based bimetallic TTFTB-MnCo-MOF 1 was directly used as the electrode material for lithium-ion batteries, which presents enhanced performance compared with the isomorphic monometallic electrodes. Comprehensive characterizations reveal that Mn(II) in 1 is beneficial to the cycling stability and Co(II) contributes to the high specific capacity. The 1||NMC 622 full cell presents a capacity of 154.9 mAh g–1 at 100 mA g–1 in the 200th cycle. 1||AC HLIC displays a high specific energy of 141.4 Wh kg–1 at a specific power of 0.25 kW kg–1 and stable cycling performance. The remarkable performance, long-term cycling stability, and low self-discharge rate of the device are greater than those of most reported HLICs.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Organic-inorganic hybrid metal-polyphenols as stable structural modules have gained extensive interest due to their diverse applications. However, titanium-oxo compounds (TOCs) with large molecular polyphenols have been less explored, and they were expected to be different from small polyphenols with isolated metal ions. Herein, 4-methyl-esculetin (Mesc), a catechol derivative, was selected to construct three TOCs, namely, [Ti17O24(Mesc)4(OiPr)16] (1), [Ti12O14(OiPr)18][Ti16O14(Mesc)12(OiPr)14] (2), and [Ti3O(Mesc)2(OAc)2(OiPr)4] (3). These compounds were structurally characterized. Photocurrent responses were evaluated using the compound-sensitized TiO2 electrodes. It was found that the current densities of 1-3 electrodes are in the order of 1 ≫ 3 > 2, which relates to the ligand-to-TiO core and ligand-to-ligand charge transfers (LMCT and LLCT, respectively). Density functional theory calculations showed that the lowest band gap of 1 originates from its LLCT. Compound 1 reacted with polyphenol tannin (TA) to form a fully transparent and robust gel (1-TA), and the gelation properties were investigated. Using the gel as a nano-TiO2 fixing agent, solar cell electrodes were prepared by a low-temperature wet method. The photocurrent responsive behavior of the 1-TA/TiO2 electrode was compared with that of the 1-sensitized traditional high-temperature-treated TiO2 electrode. Although the current density of the former is somewhat lower than that of the traditional electrode, the low-temperature wet preparation of the 1-TA/TiO2 electrode is more energy-efficient and sustainable.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Metal-organic frameworks (MOFs) have attracted noticeable attention as promising candidates for electrochemical energy storage. However, the lack of electrical conductivity and the weak stability of most MOFs result in poor electrochemical performances. Here, a tetrathiafulvalene (TTF)-based complex, formulated as [(CuCN)2(TTF(py)4)] (1) (TTF-(py)4 = tetra(4-pyridyl)-TTF), is assembled by in situ generation of coordinated CN- from a nontoxic source. Single-crystal X-ray diffraction analysis reveals that compound 1 possesses a two-dimensional layered planar structure, which is further stacked in parallel to form a three-dimensional supramolecular framework. The planar coordination environment of 1 is the first example of a TTF-based MOF. Attributed to the unique structure and redox TTF ligand, the electrical conductivity of 1 is significantly increased by 5 orders of magnitude upon iodine treatment. The iodine-treated 1 (1-ox) electrode displays typical battery-type behavior through electrochemical characterizations. The supercapattery based on the 1-ox positrode and AC negatrode presents a high specific capacity of 266.5 C g-1 at a specific current of 1 A g-1 with a remarkable specific energy of 62.9 Wh kg-1 at a specific power of 1.1 kW kg-1. The excellent electrochemical performance of 1-ox is one of the best among those reported supercapatteries, demonstrating a new strategy for developing MOF-based electrode materials.
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