Aqueous zinc-ion batteries and capacitors are potentially competitive grid-scale energy storage devices because of their great features such as safety, environmental friendliness, and low cost. Herein, a completely new phenanthroline covalent organic framework (PA-COF) was synthesized and introduced in zinc-ion supercapatteries (ZISs) for the first time. Our as-synthesized PA-COF shows a high capacity of 247 mAh g −1 at a current density of 0.1 A g −1 , with only 0.38% capacity decay per cycle during 10 000 cycles at a current density of 1.0 A g −1 . Although covalent organic frameworks (COFs) are attracting great attention in many fields, our PA-COF has been synthesized using a new strategy involving the condensation reaction of hexaketocyclohexanone and 2,3,7,8-phenazinetetramine. Detailed mechanistic investigations, through experimental and theoretical methods, reveal that the phenanthroline functional groups in PA-COF are the active zinc ion storage sites. Furthermore, we provide evidence for the cointercalation of Zn 2+ (60%) and H + (40%) into PA-COF using inductively coupled plasma atomic emission spectroscopy and deuterium solid-state nuclear magnetic resonance (NMR). We believe that this study opens a new avenue for COF material design for zinc-ion storage in aqueous ZISs.

Covalent organic frameworks (COFs) are potentially promising electrode materials for electrochemical charge storage applications thanks to their pre‐designable reticular chemistry with atomic precision, allowing precise control of pore size, redox‐active functional moieties, and stable covalent frameworks. However, studies on the mechanistic and practical aspects of their zinc‐ion storage behavior are still limited. In this study, a strategy to enhance the electrochemical performance of COF cathodes in zinc‐ion batteries (ZIBs) by introducing the quinone group into 1,4,5,8,9,12‐hexaazatriphenylene‐based COFs is reported. Electrochemical characterization demonstrates that the introduction of the quinone groups in the COF significantly pushes up the Zn2+ storage capability against H+ and elevates the average (dis‐)charge potential in aqueous ZIBs. Computational and experimental analysis further reveals the favorable redox‐active sites that host Zn2+/H+ in COF electrodes and the root cause for the enhanced electrochemical performance. This work demonstrates that molecular engineering of the COF structure is an effective approach to achieve practical charge storage performance.

Supercapacitors (SCs) are important energy storage devices that are increasingly playing an important role in various applications. [1-6] Though SCs can offer high power density, they have lower energy density in comparison to batteries. [1] The high power density makes them suitable for applications such as uninterruptible power supply (UPS), portable tools, rubber-tired gantry crane, and emergency doors on airplanes. [1,2] However, in order to deploy SCs in automotive and grid storage applications, their energy density needs to be significantly uplifted. [7,8] To enhance the energy density of SCs, which is calculated using this equation (E = 0.5 C V 2), either the specific capacitance (C) or cell voltage (V) needs to be improved. [2,9] The C values of the SC device can be improved by tuning the intrinsic properties of the electrode material. [10] For example, employing pseudocapacitive electrode materials is an effective strategy to enhance the specific capacitance (C) of the SC. [8] Pseudocapacitive materials, in general, show high capacitance values in comparison to electrical double layer capacitor (EDLC) based materials due to their fast reversible electron transfer redox reactions. [8] On the other hand, the cell voltage (V), the second major factor which influences the energy density, is greatly controlled by device engineering. [8,11] Organic electrolyte based SC devices usually offer a higher voltage window in comparison to aqueous devices. [8,11] However, the former suffers from some disadvantages such as low ionic mobility, high cost, toxicity, and not being environmentally benign. [12] On the other hand, aqueous electrolyte based SCs go without the aforementioned disadvantages, but the conventional symmetric SCs with aqueous electrolyte are hampered by low voltage windows. [12] In case of aqueous electrolyte SCs, the voltage window can be significantly improved by constructing asymmetric supercapacitors (ASCs). [12,13] In ASCs, two different electrode materials are used separately for the negative and positive electrodes. [12,13] The complementary potential windows of the individual electrodes enable the ASC device to cross the thermodynamic break New covalent organic frameworks (COFs), encompassing redox-functionalized moieties and an aza-fused π-conjugated system, are designed, synthesized, and deployed as negative electrodes in asymmetric supercapacitors (ASC), for the first time. The Hex-Aza-COFs are synthesized based on the solvothermal condensation reaction of cyclohexanehexone and redox-functionalized aromatic tetramines with benzoquinone (Hex-Aza-COF-2) or phenazine (Hex-Aza-COF-3). The redox-functionalized Hex-Aza-COFs show a specific capacitance of 585 F g −1 for Hex-Aza-COF-2 and 663 F g −1 for Hex-Aza-COF-3 in a three-electrode configuration. These values are the highest among reported COF materials and are comparable with state-of-the-art pseudocapacitive electrodes. The Hex-Aza-COFs exhibit a wide voltage window (0 to −1.0 V), which allow the construction of a two-electrode ASC device b...

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Cascade processes are gaining momentum in heterogeneous catalysis. The combination of several catalytic solids within one reactor has shown great promise for the one-step valorization of C1-feedstocks. The combination of metal-based catalysts and zeolites in the gas phase hydrogenation of CO2 leads to a large degree of product selectivity control, defined mainly by zeolites. However, a great deal of mechanistic understanding remains unclear: metal-based catalysts usually lead to complex product compositions that may result in unexpected zeolite reactivity. Here we present an in-depth multivariate analysis of the chemistry involved in eight different zeolite topologies when combined with a highly active Fe-based catalyst in the hydrogenation of CO2 to olefins, aromatics, and paraffins. Solid-state NMR spectroscopy and computational analysis demonstrate that the hybrid nature of the active zeolite catalyst and its preferred CO2-derived reaction intermediates (CO/ester/ketone/hydrocarbons, i.e., inorganic-organic supramolecular reactive centers), along with 10 MR-zeolite topology, act as descriptors governing the ultimate product selectivity.

Copper-based nanomaterials have attracted tremendous interest due to their unique properties in the fields of photoluminescence and catalysis. As a result, studies on the correlation between their molecular structure and their properties are of great importance. Copper nanoclusters are a new class of nanomaterials that can provide an atomic-level view of the crystal structure of copper nanoparticles. Herein, a high-nuclearity copper nanocluster with 81 copper atoms, formulated as [Cu81(PhS)46( t BuNH2)10(H)32]3+ (Cu 81 ), was successfully synthesized and fully studied by X-ray crystallography, X-ray photoelectron spectroscopy, hydrogen evolution experiments, electrospray ionization mass spectrometry, nuclear magnetic resonance spectroscopy, and density functional theory calculations. Cu 81 exhibits extraordinary structural characteristics, including (i) three types of novel epitaxial surface-protecting motifs; (ii) an unusual planar Cu17 core; (iii) a hemispherical shell, comprised of a curved surface layer and a planar surface layer; and (iv) two distinct, self-organized arrangements of protective ligands on the curved and planar surfaces. The present study sheds light on structurally unexplored copper nanomaterials and paves the way for the synthesis of high-nuclearity copper nanoclusters.

The production of 1-butene by ethylene dimerization is an important chemical industrial process currently implemented using homogeneous catalysts. Here, we describe a highly active heterogeneous catalyst (Ni-ZIF-8) for ethylene dimerization, which consists of isolating Ni-active sites selectively located on the crystal surface of a zeolitic imidazolate framework. Ni-ZIF-8 can be easily prepared by a simple one-pot synthesis method in which site-specific anchoring of Ni is achieved spontaneously because of the incompatibility between the d 8 electronic configuration of Ni 2+ and the three-dimensional framework of ZIF-8. The full exposure and square-planar coordination of the Ni sites accounts for the high catalytic activity of Ni-ZIF-8. It exhibits an average ethylene turnover frequency greater than 1 000 000 h −1 (1-butene selectivity >85%) at 35 °C and 50 bar, far exceeding the activities of previously reported heterogeneous catalysts and many homogeneous catalysts under similar conditions. Moreover, compared to molecular Ni complexes used as homogeneous catalysts for ethylene dimerization, Ni-ZIF-8 has significantly higher stability and shows constant activity during 4 h of continuous reaction. Isotopic labeling experiments indicate that ethylene dimerization over Ni-ZIF-8 follows the Cossee-Arlman mechanism, and detailed characterizations combined with density functional theory calculations rationalize this observed high activity.

Sunlight-driven water splitting to produce H 2 is an active field of energy research due to its promising potential to obtain renewable energy sources in a sustainable way. [1] One of the key requirements for achieving water photolysis with high "solar-tohydrogen" efficiencies is developing efficient photocatalysts. [2,3] Photoactive metal-organic frameworks (MOFs) represent one of the most promising materials for photocatalytic hydrogen production, but phosphonate-based MOFs have remained largely underdeveloped compared to other conventional MOFs. Herein, a photocatalyst of 1D titanium phosphonate MOF is designed through an easy and scalable stirring hydrothermal method. Homogeneous incorporation of organophosphonic linkers can narrow the bandgap, which is due to the strong electron-donating ability of the OH functional group that can efficiently shift the top of the valence band, moving the light absorption to the visible portion of the spectrum. In addition, the unique 1D nanowire topology enhances the photoinduced charge carrier transport and separation. Accordingly, the titanium phosphonate nanowires deliver remarkably enhanced photocatalytic hydrogen evolution activity under irradiation of both visible light and a full-spectrum simulator. Such concepts of engineering both nanostructures and electronic states herald a new paradigm for designing MOF-based photocatalysts.