Organic electrode materials are of long‐standing interest for next‐generation sustainable lithium‐ion batteries (LIBs). As a promising cathode candidate, imide compounds have attracted extensive attention due to their low cost, high theoretical capacity, high working voltage, and fast redox reaction. However, the redox active site utilization of imide electrodes remains challenging for them to fulfill their potential applications. Herein, the synthesis of a highly stable, crystalline 2D polyarylimide (2D‐PAI) integrated with carbon nanotube (CNT) is demonstrated for the use as cathode material in LIBs. The synthesized polyarylimide hybrid (2D‐PAI@CNT) is featured with abundant π‐conjugated redox‐active naphthalene diimide units, a robust cyclic imide linkage, high surface area, and well‐defined accessible pores, which render the efficient utilization of redox active sites (82.9%), excellent structural stability, and fast ion diffusion. As a consequence, high rate capability and ultrastable cycle stability (100% capacity retention after 8000 cycles) are achieved in the 2D‐PAI@CNT cathode, which far exceeds the state‐of‐the‐art polyimide electrodes. This work may inspire the development of novel organic electrodes for sustainable and durable rechargeable batteries.

Carbon electrocatalysts consisting of metal complexes such as MN or MS are promising alternatives to high-cost Pt catalysts for the hydrogen evolution reaction (HER). However, the exact HER active sites remain elusive. Here, molecular metal dithiolene-diamine (MS N , M=Co and Ni), metal bis(dithiolene) (MS ), and metal bis(diamine) (MN ) complexes were selectively incorporated into carbon-rich 2D metal-organic frameworks (2D MOFs) as model carbon electrocatalysts. The 2D MOF single layers, powders, and composites with graphene were thus prepared and showed definite active sites for H generation. The electrocatalytic HER activity of the 2D MOF-based catalysts with different metal complexes follow the order of MS N >MN >MS . Moreover, the protonation preferentially occurred on the metal atoms, and the concomitant heterolytic elimination of H was favored on the M-N units in the MS N active centers. The results provide an in-depth understanding of the catalytic active sites, thus making way for the future development of metal complexes in carbon-rich electrode materials for energy generation.

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.

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Differential conductance (dI/dV) images taken with a low-temperature scanning tunneling microscope enabled the first observation of the electron probability distribution of the molecular orbitals of a pentacene molecule directly adsorbed on a metal surface. The three highest occupied molecular orbitals (HOMO, HOMO-1, and HOMO-2) and the lowest unoccupied molecular orbital are imaged. Thus dI/dV imaging without any intervening insulating layer permits the visualization of a large variety of molecular orbitals in the electronic cloud of a wide-gap molecule physisorbed on a metal surface.

Gears are microfabricated down to diameters of a few micrometres. Natural macromolecular motors, of tens of nanometres in diameter, also show gear effects. At a smaller scale, the random rotation of a single-molecule rotor encaged in a molecular stator has been observed, demonstrating that a single molecule can be rotated with the tip of a scanning tunnelling microscope (STM). A self-assembled rack-and-pinion molecular machine where the STM tip apex is the rotation axis of the pinion was also tested. Here, we present the mechanics of an intentionally constructed molecule-gear on a Au(111) surface, mounting and centring one hexa-t-butyl-pyrimidopentaphenylbenzene molecule on one atom axis. The combination of molecular design, molecular manipulation and surface atomic structure selection leads to the construction of a fundamental component of a planar single-molecule mechanical machine. The rotation of our molecule-gear is step-by-step and totally under control, demonstrating nine stable stations in both directions.

above. Organic crystals are one of the strong contenders for nanophotonic applications due to the impressive advantages they offer, such as tailor-made synthesis, engineered flexibility, chirality, optical (linear and nonlinear) properties, high photoluminescence efficiency, lightweight, easy processability (solution or sublimation), and relatively high refractive index, n (n = √ε; where ε is the dielectric permittivity of the materials). [1] The customized synthesis of building block molecules offers fine-tuning of the optical absorbance and emission from ultraviolet (UV) to near-infrared (NIR) region of the electromagnetic spectrum by anchoring specific electron donor (D) and electron acceptor (A) groups to π-conjugated molecular backbone of varying lengths. Organic crystals with D and A functional groups also provide nonlinear optical (NLO) emissions (via multiphoton excitation process) depending upon the molecular symmetry and solid-state molecular packing (centrosymmetric/nonsymmetric). Besides, the polar and non-polar nature of the functional groups allows varying solubility of the organic compounds in a range of solvents facilitating solution processability. Depending upon the degree of solubility, organic compounds can be processed into microstructures (of various dimensions and sizes) suitable for nano-/micro-photonic applications using solvent-assisted selfassembly or crystal growth technique. Sublimation is also an alternative clean method to process organic compounds into crystalline microstructures. [2c] Naturally, most of the organic crystals are stiff, and they reveal their fragility when subjected to external stress beyond a specific limit. Therefore, until now, most of the devices fabricated with organic crystalline materials are rigid. [8] However, future "intelligent" technologies mandate flexible devices. The forecasted market for such devices is expected to touch over $70 billion by 2026. [9] Crystals with unusual mechanical flexibility (reversible) will open new avenues for applications in flexible organic electronics and photonic devices. [10-13] On the other hand, the rarity of the flexible crystal is one of the major impediment to the advancement of flexible nano-/micro-photonic device components. Seamless integration of a flexible crystal in a microcircuit needs precise spatial control of crystal position and its geometry. [13] However, the dearth of appropriate micromanipulation technique (mechanical or optical trapping) is a significant impediment to the shaping of flexible microcrystals for circuit applications.

Covalent organic frameworks (COFs) have garnered immense scientific interest among porous materials because of their structural tunability and diverse properties. However,the response of such materials towardlaser-induced nonlinear optical (NLO) applications is hardly understood and demands prompt attention. Three novel regioregular porphyrin (Por)-based porous COFs-Por-COF-HH and its dual metalated congeners Por-COF-ZnCu and Por-COF-ZnNi-have been prepared and present excellent NLO properties.N otably,i ntensity-dependent NLO switching behavior was observed for these Por-COFs,w hichi sh ighly desirable for optical switching and optical limiting devices. Moreover,t he efficient p-conjugation and charge-transfer transition in ZnCu-Por-COF enabled ahigh nonlinear absorption coefficient (b = 4470 cm/GW) and figure of merit (FOM = s 1 /s o ,3565) value compared to other state-of-the-art materials, including molecular porphyrins (b % 100-400 cm/GW), metalorganic frameworks (MOFs; b % 0.3-0.5 cm/GW), and graphene (b = 900 cm/GW). Molecules/materialswithinherentnonlinearoptical(NLO)properties have profound importance in telecommunications, data storage,d isplay technologies,s ensors,a nd biomedical devices. [1] In this regard, molecular porphyrins have been widely studied because of their versatile optical and electrochemical properties,large and fast NLO responses,possibility of incorporating aw ide range of metals,a nd their good thermochemical stabilities for optical limiting and optical switching applications. [2] Nonetheless,t oenhance and tune optical nonlinearities of singular porphyrin moieties,b athochromic shifting of their absorption bands by large p-electron delocalization is crucial, which becomes possible through de novo design of integrated porphyrin units featuring extended p-conjugation. [3, 4] Along this line,w ep ropose ap orphyrin-linked covalent organic framework (COF) [5] as model system, wherein enhancement and switching of the NLO response can be studied by manipulation of the framework. Among the recognized crystalline materials, COFs are known for being mechanically robust and offering ahighly accessible surface area. Thestructural and electronic tunability of COFs have garnered particular interest in research areas such as adsorption/storage, [6] chemical sensors, [7] electronics, [8] and catalysis. [9] Despite such potential, COFs comprising porphyrin units have not been explored as NLO materials.F or this purpose,aregioregular ordering of multiple metal centers in ac rystalline 2D porphyrin framework-preferably without ap ost-synthetic modification-is desirable.T his challenging objective [10] has great potential in optoelectronics and photo/electrocatalysis applications.Herein, we present aconjugated imine-linked porphyrinhomopolymeric COF (Por-COF-HH; Figure 1a)prepared by Schiff base A4B4 condensation of 5,10,15,20-tetrakis(4-formylphenyl)-21H,23H-porphyrin (TFPP) and 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin (TAPP). Adopting the same pathway,w ea lso synthesized regioregular...