Electrifying HCOOH synthesis from CO2 building blocks over Cu-Bi nanorod arrays.

Precise electrochemical synthesis of commodity chemicals and fuels from CO2 building blocks provides a promising route to close the anthropogenic carbon cycle, in which renewable but intermittent electricity could be stored within the greenhouse gas molecules. Here, we report state-of-the-art CO2-to-HCOOH valorization performance over a multiscale optimized Cu-Bi cathodic architecture, delivering a formate Faradaic efficiency exceeding 95% within an aqueous electrolyzer, a C-basis HCOOH purity above 99.8% within a solid-state electrolyzer operated at 100 mA cm-2 for 200 h and an energy efficiency of 39.2%, as well as a tunable aqueous HCOOH concentration ranging from 2.7 to 92.1 wt%. Via a combined two-dimensional reaction phase diagram and finite element analysis, we highlight the role of local geometries of Cu and Bi in branching the adsorption strength for key intermediates like *COOH and *OCHO for CO2 reduction, while the crystal orbital Hamiltonian population analysis rationalizes the vital contribution from moderate binding strength of η2(O,O)-OCHO on Cu-doped Bi surface in promoting HCOOH electrosynthesis. The findings of this study not only shed light on the tuning knobs for precise CO2 valorization, but also provide a different research paradigm for advancing the activity and selectivity optimization in a broad range of electrosynthetic systems.

In Situ Visual Observation of Surface Energy-Controlled Heterogeneous Nucleation of Metal Nanocrystals.

Electrochemical growth of metal nanocrystals is pivotal for material synthesis, processing, and resource recovery. Understanding the heterogeneous interface between electrolyte and electrode is crucial for nanocrystal nucleation, but the influence of this interaction is still poorly understood. This study employs advanced in situ measurements to investigate the heterogeneous nucleation of metals on solid surfaces. By observing the copper nanocrystal electrodeposition, an interphase interaction-induced nucleation mechanism highly dependent on substrate surface energy is uncovered. It shows that a high-energy (HE) electrode tended to form a polycrystalline structure, while a low-energy (LE) electrode induced a monocrystalline structure. Raman and electrochemical characterizations confirmed that HE interface enhances the interphase interaction, reducing the nucleation barrier for the sturdy nanostructures. This leads to a 30.92-52.21% reduction in the crystal layer thickness and a 19.18-31.78% increase in the charge transfer capability, promoting the formation of a uniform and compact film. The structural compactness of the early nucleated crystals enhances the deposit stability for long-duration electrodeposition. This research not only inspires comprehension of physicochemical processes correlated with heterogeneous nucleation, but also paves a new avenue for high-quality synthesis and efficient recovery of metallic nanomaterials.

Synthesis of a Dicyclohepta[a,g]heptalene-Containing Polycyclic Conjugated Hydrocarbon and the Impact of Non-Alternant Topologies.

Incorporating non-hexagonal rings into polycyclic conjugated hydrocarbons (PCHs) can significantly affect their electronic and optoelectronic properties and chemical reactivities. Here, we report the first bottom-up synthesis of a dicyclohepta[a,g]heptalene-embedded PCH (1) with four continuous heptagons, which are arranged in a "Z" shape. Compared with its structural isomer bischrysene 1 R with only hexagonal rings, compound 1 presents a distinct antiaromatic character, especially the inner heptalene core, which possesses clear antiaromatic nature. In addition, PCH 1 exhibits a narrower highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap than its benzenoid contrast 1 R, as verified by experimental measurements and theoretical calculations. Our work reported herein not only provides a new way to synthesize novel PCHs with non-alternant topologies but also offers the possibility to tune their electronic and optical properties.

Titanium-Mediated aza-Nazarov Annulation for the Synthesis of N-Fused Tricycles: A General Method to Access Lamellarin Analogues.

Fused heterocycles with nitrogen incorporation are of particular bioactive use and high importance in many research fields, especially isoquinoline-based [6/6/5] tricycles. Here, we report a unique strategy to access multifunctional N-fused tricycles from α,ß-unsaturated isoquinoline ketone and sulfonamide under mild reaction conditions. The methodology features wide substrate tolerance, and a set of N-fused heteroarenes including quinoline, phthalazine, quinazoline, quinoxaline, and benzothiazole cores are furnished efficiently. Moreover, the protocol is easy to scale up to synthesize lamellarin analogues, and the amide group of the product is also easy to transfer to other functional groups.

Two-Fold Interlocking Cationic Metal-Organic Framework Material with Exchangeable Chloride for Perrhenate/Pertechnetate Sorption.

Albeit reported substantial sorbents for elimination of TcO4-, the issue of secondary contamination caused by released counterions (such as NO3-) from the cationic metal-organic framework (MOF) has not come into the sufficient limelight for researchers. Herein, our efforts are dedicated to settle the matter through synthesis of NiCl2 based on the cationic MOF (ZJU-X4). Less harmful chlorides are used as exchangeable anions for replacing hazardous anions. Notably, ZJU-X4 exhibited fast sorption kinetics, high sorption capacity of 395 mg/g, decent selectivity, and excellent reusability in four recycles. The results of ion chromatography revealed that the released chloride ion was equal to sorption of target ions, and pair distribution functions were employed to analyze the changes in ZJU-X4 after sorption of ReO4-, clearly elucidating the anion-exchange mechanism. Furthermore, in the dynamic sorption experiments, ReO4- could be facilely and effectively removed and recovered, showing the value of practical applications. This work indicated that cationic MOF-based metal chloride salts would be a better choice for anionic sorbents.

Synthesis and Visualization of Entangled 3D Covalent Organic Frameworks with High-Valency Stereoscopic Molecular Nodes for Gas Separation.

The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with Td , D3h , D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high-valency quadrangular prism (D4h ) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine-linked COFs can be created. Low-dose electron microscopy allows the direct visualization of their 2-fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2 H2 /CO2 and C2 H2 /CH4 gas pairs. The introduction of high-valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.

Unravelling surface and interfacial structures of a metal-organic framework by transmission electron microscopy.

Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how ZIF-8 crystals self-assemble and the subsequent influence of interfacial cavities on mass transport of guest molecules.

Ultralow Self-Doping in Two-dimensional Hybrid Perovskite Single Crystals.

Unintentional self-doping in semiconductors through shallow defects is detrimental to optoelectronic device performance. It adversely affects junction properties and it introduces electronic noise. This is especially acute for solution-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of the two-dimensional perovskites (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3)n-1 (n = 1, 2, and 3), over three orders of magnitude lower than those of typical three-dimensional hybrid perovskites, by analyzing their conductivity behavior. We propose that crystallization of hybrid perovskites containing large organic cations suppresses defect formation and thus favors a low self-doping level. To exemplify the benefits of this effect, we demonstrate extraordinarily high light-detectivity (1013 Jones) in (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3)n-1 photoconductors due to the reduced electronic noise, which makes them particularly attractive for the detection of weak light signals. Furthermore, the low self-doping concentration reduces the equilibrium charge carrier concentration in (C6H5C2H4NH3)2PbI4·(CH3NH3PbI3)n-1, advantageous in the design of p-i-n heterojunction solar cells by optimizing band alignment and promoting carrier depletion in the intrinsic perovskite layer, thereby enhancing charge extraction.

Engineering of CH3 NH3 PbI3 Perovskite Crystals by Alloying Large Organic Cations for Enhanced Thermal Stability and Transport Properties.

The number of studies on organic-inorganic hybrid perovskites has soared in recent years. However, the majority of hybrid perovskites under investigation are based on a limited number of organic cations of suitable sizes, such as methylammonium and formamidinium. These small cations easily fit into the perovskite's three-dimensional (3D) lead halide framework to produce semiconductors with excellent charge transport properties. Until now, larger cations, such as ethylammonium, have been found to form 2D crystals with lead halide. Here we show for the first time that ethylammonium can in fact be incorporated coordinately with methylammonium in the lattice of a 3D perovskite thanks to a balance of opposite lattice distortion strains. This inclusion results in higher crystal symmetry, improved material stability, and markedly enhanced charge carrier lifetime. This crystal engineering strategy of balancing opposite lattice distortion effects vastly increases the number of potential choices of organic cations for 3D perovskites, opening up new degrees of freedom to tailor their optoelectronic and environmental properties.

Chiral gold nanowires with Boerdijk-Coxeter-Bernal structure.

A Boerdijk-Coxeter-Bernal (BCB) helix is made of linearly stacked regular tetrahedra (tetrahelix). As such, it is chiral without nontrivial translational or rotational symmetries. We demonstrate here an example of the chiral BCB structure made of totally symmetrical gold atoms, created in nanowires by direct chemical synthesis. Detailed study by high-resolution electron microscopy illustrates their elegant chiral structure and the unique one-dimensional "pseudo-periodicity". The BCB-type atomic packing mode is proposed to be a result of the competition and compromise between the lattice and surface energy.

Building Chemical Interface Layers in Functionalized Graphene Oxide/Rubber Composites to Achieve Enhanced Mechanical Properties and Thermal Control Capability of Tires.

With the rapid development of the transport industry, there is a higher demand for environmental friendliness, durability, and stability of tires. Rubber composites with excellent mechanical properties, abrasion resistance, and low heat generation are very important for the preparation of green tires. In this study, the all-aqueous phase process was initially employed to prepare 2-Amino-5-mercapto-1,3,4-thiadiazole (AZT) functionalized graphene oxide (AGO). Subsequently, modified graphene oxide/silica/natural rubber (AGO/SiO2/NR) composites were obtained through latex blending and hot press vulcanization processes. This method was environmentally friendly and exhibited high modification efficiency. Benefiting from the good dispersion of AGO in the latex and the cross-linking reaction between AGO and NR, AGO/SiO2/NR composites with good dispersion and enhanced interfacial interaction were finally obtained. AGO/SiO2/NR composites showed significantly improved overall performance. Compared to GO/SiO2/NR composites, the tensile strength (28.1 MPa) and tear strength (75.3 N/mm) of the AGO/SiO2/NR composites were significantly increased, while the heat build-up value (10.4 °C) and DIN abrasion volume (74.9 mm3) were significantly reduced. In addition, the steady-state temperature field distribution inside the tire was visualized by ANSYS finite element simulation. The maximum temperature of the prepared AGO/SiO2/NR was reduced by 18.2% compared to that of the GO/SiO2/NR tires. This strategy is expected to provide a new approach for the development of low energy consumption, environmentally friendly, and long-life rubber for tires.

How specific ion effects influence the mechanical behaviors of amide macromolecules? A cross-scale study.

The mechanisms of specific ion effects on the properties of amide macromolecules is essential to understanding the evolution of life. Because most biological macromolecules contain both complex hydrophilic and hydrophobic structures, it is challenging to accurately identify the contributions of molecular structure to macroscopic behaviors. Herein, we investigated the influence of specific ion effects on the mechanical behaviors of poly(N-isopropylacrylamide) and neutral polyacrylamide (i.e., PNIPAM and NPAM), through a cross-scale study that includes single-molecule force spectroscopy, molecular dynamics simulation and macro mechanical method. The results indicate that the molecular conformation can be markedly influenced by the hydrophilicity (or hydrophobicity) of both macromolecule chain and ions. An extended chain conformation can be obtained when the side groups and ions are relatively hydrophilic, which can also increase the elasticity of a macromolecule chain and film materials. The relatively hydrophobic components promote the collapse of macromolecule chains and reduce the molecular elasticity. It is believed that the hydrogen bonding intensity between a macromolecule chain and aquated ions controls the chain conformation and the elasticity of molecules and films. This study is not only helpful for understanding the self-assembly mechanism of organisms but also provides a way to associate the molecular properties with the macroscopic performance of materials.

A high-performance watermelon skin ion-solvating membrane for electrochemical CO2 reduction.

Ion-solvating membranes have been gaining increasing attention as core components of electrochemical energy conversion and storage devices. However, the development of ion-solvating membranes with low ion resistance and high ion selectivity still poses challenges. In order to propose an effective strategy for high-performance ion-solvating membranes, this study conducted a comprehensive investigation on watermelon skin membranes through a combination of experimental research and molecular dynamics simulation. The micropores and continuous hydrogen-bonding networks constructed by the synergistic effect of cellulose fiber and pectin enable the hypodermis of watermelon skin membranes to have a high ion conductivity of 282.3 mS cm-1 (room temperature, saturated with 1 M KOH). The negatively charged groups and hydroxyl groups on the microporous channels increase the formate penetration resistance of watermelon skin membranes in contrast to commercially available membranes, and this is crucial for CO2 electroreduction. Therefore, the confinement of proton donors and negatively charged groups within three-dimensional microporous polymers gives inspiration for the design of high-performance ion-solvating membranes.

Phosphine-Catalyzed Allylic Alkylation of (Hetero)Aryl Alkynes with Pronucleophiles: Concise Total Synthesis of (±)-Esermethole.

Allylic alkylations are valuable in the construction of versatile carbon-carbon bonds, which are mostly catalyzed by noble transition metals with additional waste byproduct generation. Here, we present the first organophosphine-catalyzed allylic alkylation of (hetero)aryl alkynes with various carbo-nucleophiles. The methodology is highly atom economical and compatible with a wide substrate scope (more than 38 examples). Moreover, the reaction could be easily scaled up, and deuterium labeling experiments have been conducted to elucidate the plausible mechanism. Finally, the protocol has been utilized to achieve the concise total synthesis of natural product (±)-esermethole.

Surprising Nanomechanical and Conformational Transition of Neutral Polyacrylamide in Monovalent Saline Solutions.

Polyacrylamide (PAM) is one of the most important water-soluble polymers that has been extensively applied in water treatment, drug delivery, and flexible electronic devices. The basic properties, e.g., microstructure, nanomechanics, and solubility, are deeply involved in the performance of PAM materials. Current research has paid more attention to the development and expansion of the macroscopic properties of PAM materials, and the study of the mechanism involved with the roles of water and ions on the properties of PAM is insufficient, especially for the behaviors of neutral amide side groups. In this study, single molecule force spectroscopy was combined with molecular dynamic (MD) simulations, atomic force microscope imaging, and dynamic light scattering to investigate the effects of monovalent ions on the nanomechanics and molecular conformations of neutral PAM (NPAM). These results show that the single-molecule elasticity and conformation of NPAM exhibit huge variation in different monovalent salt solutions. NPAM adopts an extended conformation in aqueous solutions of strong hydrated ion (acetate), while transforms into a collapse globule in the existence of weakly hydrated ion (SCN-). It is believed that the competition between intramolecular and intermolecular weak interactions plays a key role to adjust the molecular conformation and elasticity of NPAM. The competition can be largely influenced by the type of monovalent ions through hydration or a chaotropic effect. Methods utilized in this study provide a means to better understand the Hofmeister effect of ions on other macromolecules containing amide groups at the single-molecule level.

Formation of polyrotaxane crystals driven by dative boron-nitrogen bonds.

The integration of mechanically interlocked molecules (MIMs) into purely organic crystalline materials is expected to produce materials with properties that are not accessible using more classic approaches. To date, this integration has proved elusive. We present a dative boron-nitrogen bond-driven self-assembly strategy that allows for the preparation of polyrotaxane crystals. The polyrotaxane nature of the crystalline material was confirmed by both single-crystal x-ray diffraction analysis and cryogenic high-resolution low-dose transmission electron microscopy. Enhanced softness and greater elasticity are seen for the polyrotaxane crystals than for nonrotaxane polymer controls. This finding is rationalized in terms of the synergetic microscopic motion of the rotaxane subunits. The present work thus highlights the benefits of integrating MIMs into crystalline materials.

Lattice-Gradient Perovskite KTaO3 Films for an Ultrastable and Low-Dose X-Ray Detector.

Conventional indirect X-ray detectors employ scintillating phosphors to convert X-ray photons into photodiode-detectable visible photons, leading to low conversion efficiencies, low spatial resolutions, and optical crosstalk. Consequently, X-ray detectors that directly convert photons into electric signals have long been desired for high-performance medical imaging and industrial inspection. Although emerging hybrid inorganic-organic halide perovskites, such as CH3 NH3 PbI3 and CH3 NH3 PbBr3 , exhibit high sensitivity, they have salient drawbacks including structural instability, ion motion, and the use of toxic Pb. Here, this work reports an ultrastable, low-dose X-ray detector comprising KTaO3 perovskite films epitaxially grown on a Nb-doped strontium titanate substrate using a low-cost solution method. The detector exhibits a stable photocurrent under high-dose irradiation, high-temperature (200 °C), and aqueous conditions. Moreover, the prototype KTaO3 -film-based detector exhibits a 150-fold higher sensitivity (3150 µC Gyair -1 cm-2 ) and 150-fold lower detection limit (<40 nGyair s-1 ) than those of commercial α-Se-based direct detectors. Systematic investigations reveal that the high stability of the detector originates from the strong covalent bonds within the KTaO3 film, whereas the low detection limit is due to a lattice-gradient-driven built-in electric field and the high insulating property of KTaO3 film. This study unveils a new path toward the fabrication of green, stable, and low-dose X-ray detectors using oxide perovskite films, which have significant application potential in medical imaging and security operations.

Ultrahigh Kinetic Inductance Superconducting Materials from Spinodal Decomposition.

Disordered superconducting nitrides with kinetic inductance have long been considered to be leading material candidates for high-inductance quantum-circuit applications. Despite continuing efforts toward reducing material dimensions to increase the kinetic inductance and the corresponding circuit impedance, achieving further improvements without compromising material quality has become a fundamental challenge. To this end, a method to drastically increase the kinetic inductance of superconducting materials via spinodal decomposition while maintaining a low microwave loss is proposed. Epitaxial Ti0.48 Al0.52 N is used as a model system and the utilization of spinodal decomposition to trigger the insulator-to-superconductor transition with a drastically enhanced material disorder is demonstrated. The measured kinetic inductance increases by two to three orders of magnitude compared with the best disordered superconducting nitrides reported to date. This work paves the way for substantially enhancing and deterministically controlling the inductance for advanced superconducting quantum circuits.

Unusual Activity of Rationally Designed Cobalt Phosphide/Oxide Heterostructure Composite for Hydrogen Production in Alkaline Medium.

Design and development of an efficient, nonprecious catalyst with structural features and functionality necessary for driving the hydrogen evolution reaction (HER) in an alkaline medium remain a formidable challenge. At the root of the functional limitation is the inability to tune the active catalytic sites while overcoming the poor reaction kinetics observed under basic conditions. Herein, we report a facile approach to enable the selective design of an electrochemically efficient cobalt phosphide oxide composite catalyst on carbon cloth (CoP-CoxOy/CC), with good activity and durability toward HER in alkaline medium (η10 = -43 mV). Theoretical studies revealed that the redistribution of electrons at laterally dispersed Co phosphide/oxide interfaces gives rise to a synergistic effect in the heterostructured composite, by which various Co oxide phases initiate the dissociation of the alkaline water molecule. Meanwhile, the highly active CoP further facilitates the adsorption-desorption process of water electrolysis, leading to extremely high HER activity.

Unprecedented Surface Plasmon Modes in Monoclinic MoO2 Nanostructures.

Developing stable plasmonic materials featuring earth-abundant compositions with continuous band structures, similar to those of typical metals, has received special research interest. Owing to their metal-like behavior, monoclinic MoO2 nanostructures have been found to support stable and intense surface plasmon (SP) resonances. However, no progress has been made on their energy and spatial distributions over individual nanostructures, nor the origin of their possibly existing specific SP modes. Here, various MoO2 nanostructures are designed via polydopamine chemistry and managed to visualize multiple longitudinal and transversal SP modes supported by the monoclinic MoO2 , along with intrinsic interband transitions, using scanning transmission electron microscopy coupled with ultrahigh-resolution electron energy loss spectroscopy. The identified geometry-dependent SP energies are tuned by either controlling the shape and thickness of MoO2 nanostructures through their well-designed chemical synthesis, or by altering their length using a developed electron-beam patterning technique. Theoretical calculations reveal that the strong plasmonic behavior of the monoclinic MoO2 is associated with the abundant delocalized electrons in the Mo d orbitals. This work not only provides a significant improvement in imaging and tailoring SPs of nonconventional metallic nanostructures, but also highlights the potential of MoO2 nanostructures for micro-nano optical and optoelectronic applications.