Rechargeable aqueous Zn-ion energy storage devices are promising candidates for next-generation energy storage technologies. However, the lack of highly reversible Zn2+-storage anode materials with low potential windows remains a primary concern. Here, we report a two-dimensional polyarylimide covalent organic framework (PI-COF) anode with high-kinetics Zn2+-storage capability. The well-organized pore channels of PI-COF allow the high accessibility of the build-in redox-active carbonyl groups and efficient ion diffusion with a low energy barrier. The constructed PI-COF anode exhibits a specific capacity (332 C g–1 or 92 mAh g–1 at 0.7 A g–1), a high rate capability (79.8% at 7 A g–1), and a long cycle life (85% over 4000 cycles). In situ Raman investigation and first-principle calculations clarify the two-step Zn2+-storage mechanism, in which imide carbonyl groups reversibly form negatively charged enolates. Dendrite-free full Zn-ion devices are fabricated by coupling PI-COF anodes with MnO2 cathodes, delivering excellent energy densities (23.9 ∼ 66.5 Wh kg–1) and supercapacitor-level power densities (133 ∼ 4782 W kg–1). This study demonstrates the feasibility of covalent organic framework as Zn2+-storage anodes and shows a promising prospect for constructing reliable aqueous energy storage devices.

Three unprecedented helical nanographenes (1, 2, and 3) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X‐ray crystallographic analysis. The embedded azulene unit in 2 possesses a record‐high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis‐spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps (2: 1.88 eV; 3: 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in‐situ EPR/Vis–NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties.

Rechargeable aluminium (Al) batteries (RABs) have long‐been pursued due to the high sustainability and three‐electron‐transfer properties of Al metal. However, limited redox chemistry is available for rechargeable Al batteries, which restricts the exploration of cathode materials. Herein, we demonstrate an efficient Al–amine battery based on a quaternization reaction, in which nitrogen (radical) cations (R3N.+ or R4N+) are formed to store the anionic Al complex. The reactive aromatic amine molecules further oligomerize during cycling, inhibiting amine dissolution into the electrolyte. Consequently, the constructed Al–amine battery exhibits a high reversible capacity of 135 mAh g−1 along with a superior cycling life (4000 cycles), fast charge capability and a high energy efficiency of 94.2 %. Moreover, the Al–amine battery shows excellent stability against self‐discharge, far beyond conventional Al–graphite batteries. Our findings pave an avenue to advance the chemistry of RABs and thus battery performance.

The structure of emeraldine salt and emeraldine bases with different molar weight and their behavior in electrochemical doping was studied by different spectroscopic and spectroelectrochemical techniques. By Fourier transform infrared (FTIR) spectroscopy, the branching of the polymer chain at tri- and tetrasubstituted benzene rings as well as the presence of small amounts of phenazine units are shown. The branching of the polymer chains increases with the increasing of the molar weight of emeraldines. The optical transitions in protonated and unprotonated emeraldine were studied by ultraviolet-visible near-infrared (UV-vis NIR) spectroscopy. By comparison of the electron spin resonance (ESR) spectra of emeraldine in protic solvents and acidic solutions, the emeraldine bases are shown to be to some extent protonated. Applying in situ ESR-UV-vis NIR spectroelectrochemistry, the charged states in emeraldines upon p-doping were investigated considering the influence of the nonideal "linear" polymer structures. The initial stage of oxidation of the emeraldine base and salt consists of the different charged states. The phenazine units in the polymer chains stabilize the charged states in the emeraldines upon p-doping.

The disinfection of bacteria by thermally excited pyroelectric materials in aqueous environments provides opportunities for the development of new means of sanitization. However, little is known about the formation of reactive oxygen species (ROS) at the surface of the thermally excited pyroelectric materials. To investigate the pyroelectrically driven ROS generation we performed OH radical specific measurements of thermally stimulated barium titanate nanoparticles in contact with palladium nanoparticles. Through electron spin resonance measurements with the spin trap BMPO (5-tert-butoxycarbonyl 5-methyl-1-pyrroline n-oxide) and fluorescence spectroscopy of 7-hydroxycoumarin, OH radical generation was detected, which confirms the hypothesis of pyroelectric ROS production. Since pyroelectric potential changes are insufficient for direct electrochemical OH radical generation, we propose a two-step chargetransfer model facilitated by intermittent contact between the palladium and the pyroelectric nanoparticles and the pyroelectric effect as the driving force for charge transfer. ■ INTRODUCTIONCommercial water disinfection currently relies on chemical methods using chlorine-or ozone-based chemicals, whereas physical methods like thermal disinfection or ultraviolet radiation are less often employed. Due to their high oxidative potential, reactive oxygen species (ROS) are well suited as a physical means of disinfection. A completely new approach for creating ROS is the utilization of the pyroelectric effect, 1 which seems favorable when naturally occurring temperature changes can be employed for the excitation of the pyroelectric materials and, thus, offer an environmentally friendly method of water disinfection.In an aqueous solution the spontaneous polarization at the surface of a ferroelectric is screened, for example, by dissolved ions or dissociated water molecules. Changes in temperature trigger the pyroelectric effect. The imbalance of polarization and screening charges changes the effective surface potential. It was shown that these potential changes whether they stem from changes in temperature or strain can be used to drive electrochemistry between physisorbed molecular species. 1,2 For example Hong et al. demonstrated water splitting on mechanically excited surfaces of BaTiO 3 and ZnO. Gutmann et al. proposed that the observed water disinfection with thermally stimulated LiNbO 3 and LiTaO 3 is facilitated by production of ROS at the surface of the pyroelectric materials.Free radicals have high oxidation potentials, especially the OH radical whose oxidation potential is twice that of chlorine which is commonly used for disinfection. It is known that OH radicals can pull H atoms from C−H and S−H bonds and split aromatic rings. Living cells are damaged by radicals reacting with amino acids and DNA molecules. 3 Photocatalytic E. coli inactivation with TiO 2 showed cell damage caused by various ROS, such as OH radicals, hyperoxide radicals, and H 2 O 2 . 4 Basically ROS react immediately at the place of their ori...