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Selective producing ethanol from CO 2 electroreduction is highly demanded, yet the competing ethylene generation route is commonly more thermodynamically preferred. Herein, we reported an efficient CO 2 -to-ethanol conversion (53.5 % faradaic efficiency at -0.75 V versus reversible hydrogen electrode (vs. RHE)) over an oxide-derived nanocubic catalyst featured with abundant "embossment-like" structured grain-boundaries. The catalyst also attains a 23.2 % energy efficiency to ethanol within a flow cell reactor. In situ spectroscopy and electrochemical analysis identified that these dualphase Cu(I) and Cu(0) sites stabilized by grain-boundaries are very robust over the operating potential window, which maintains a high concentration of co-adsorbed *CO and hydroxyl (*OH) species. Theoretical calculations revealed that the presence of *OH ad not only promote the easier dimerization of *CO to form *OCCO (ΔG~0.20 eV) at low overpotentials but also preferentially favor the key *CHCOH intermediate hydrogenation to *CHCHOH (ethanol pathway) while suppressing its dehydration to *CCH (ethylene pathway), which is believed to determine the remarkable ethanol selectivity. Such imperative intermediates associated with the bifurcation pathway were directly distinguished by isotope labelling in situ infrared spectroscopy. Our work promotes the understanding of bifurcating mechanism of CO 2 ER-to-hydrocarbons more deeply, providing a feasible strategy for the design of efficient ethanol-targeted catalysts., (© 2024 Wiley-VCH GmbH.)

The instability of the solid electrolyte interface (SEI) is a critical challenge for the zinc metal anodes, leading to an erratic electrode/electrolyte interface and hydrogen evolution reaction (HER), ultimately resulting in anode failure. This study uncovers that the fluorine species dissolution is the root cause of SEI instability. To effectively suppress the F - dissolution, an introduction of a low-polarity molecule, 1,4-thioxane (TX), is proposed, which reinforces the stability of the fluorine-rich SEI. Moreover, the TX molecule has a strong affinity for coordinating with Zn 2+ and adsorbing at the electrode/electrolyte interface, thereby diminishing the activity of local water and consequently impeding SEI dissolution. The robust fluorine-rich SEI layer promotes the high durability of the zinc anode in repeated plating/stripping cycles, while concurrently suppressing HER and enhancing Coulombic efficiency. Notably, the symmetric cell with TX demonstrates exceptional electrochemical performance, sustaining over 500 hours at 20 mA cm -2 with 10 mAh cm -2 . Furthermore, the Zn||KVOH full cell exhibits excellent capacity retention, averaging 6.8 mAh cm -2 with 98 % retention after 400 cycles, even at high loading with a lean electrolyte. This work offers a novel perspective on SEI dissolution as a key factor in anode failure, providing valuable insights for the electrolyte design in energy storage devices., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The electrochemical CO 2 reduction reaction (eCO 2 RR) to multicarbon products has been widely recognized for Cu-based catalysts. However, the structural changes in Cu-based catalysts during the eCO 2 RR pose challenges to achieving an in-depth understanding of the structure-activity relationship, thereby limiting catalyst development. Herein, we employ constant-potential density functional theory calculations to investigate the sintering process of Cu single atoms of Cu-N-C single-atom catalysts into clusters under eCO 2 RR conditions. Systematic constant-potential ab initio molecular dynamics simulations revealed that the leaching of Cu-(CO) x moieties and subsequent agglomeration into clusters can be facilitated by synergistic adsorption of H and eCO 2 RR intermediates (e.g., CO). Increasing the Cu 2+ concentration or the applied potential can efficiently suppress Cu sintering. Both microkinetic simulations and experimental results further confirm that sintered Cu clusters play a crucial role in generating C 2 products. These findings provide significant insights into the dynamic evolution of Cu-based catalysts and the origin of their activity toward C 2 products during the eCO 2 RR., (© 2024 Wiley-VCH GmbH.)

Li-CO 2 batteries are regarded as promising high-energy-density energy conversion and storage devices, but their practicability is severely hindered by the sluggish CO 2 reduction/evolution reaction (CORR/COER) kinetics. Due to the various crystal structures and unique electronic configuration, Mn-based cathode catalysts have shown considerable competition to facilitate CORR/COER. However, the specific active sites and regulation principle of Mn-based catalysts remain ambiguous and limited. Herein, this work designs novel Mn dual-active sites (MOC) supported on N-doped carbon nanofibers and conduct a comprehensive investigation into the underlying relationship between different Mn active sites and their electrochemical performance in Li-CO 2 batteries. Impressively, this work finds that owing to the in situ generation and stable existence of Mn(III), MOC undergoes obvious electrochemical reconstruction during battery cycling. Moreover, a series of characterizations and theoretical calculations demonstrate that the different electronic configurations and coordination environments of Mn(II) and Mn(III) are conducive to promoting CORR and COER, respectively. Benefiting from such a modulating behavior, the Li-CO 2 batteries deliver a high full discharge capacity of 10.31 mAh cm -2 , and ultra-long cycle life (327 cycles/1308 h). This fundamental understanding of MOC reconstruction and the electrocatalytic mechanisms provides a new perspective for designing high-performance multivalent Mn-integrated hybrid catalysts for Li-CO 2 batteries., (© 2024 Wiley‐VCH GmbH.)

The high-current-density Zn-air battery shows big prospects in next-generation energy technologies, while sluggish O 2 reaction and diffusion kinetics barricade the applications. Herein, the sequential assembly is innovatively demonstrated for hierarchically mesoporous molybdenum carbides/carbon microspheres with a tunable thickness of mesoporous carbon layers (Meso-Mo 2 C/C-x, where x represents the thickness). The optimum Meso-Mo 2 C/C-14 composites (≈2 µm in diameter) are composed of mesoporous nanosheets (≈38 nm in thickness), which possess bilateral mesoporous carbon layers (≈14 nm in thickness), inner Mo 2 C/C layers (≈8 nm in thickness) with orthorhombic Mo 2 C nanoparticles (≈2 nm in diameter), a high surface area of ≈426 m 2  g -1 , and open mesopores (≈6.9 nm in size). Experiments and calculations corroborate the hierarchically mesoporous Mo 2 C/C can enhance hydrophilicity for supplying sufficient O 2 , accelerate oxygen reduction kinetics by highly-active Mo 2 C and N-doped carbon sites, and facilitate O 2 diffusion kinetics over hierarchically mesopores. Therefore, Meso-Mo 2 C/C-14 outputs a high half-wave potential (0.88 V vs RHE) with a low Tafel slope (51 mV dec -1 ) for oxygen reduction. More significantly, the Zn-air battery delivers an ultrahigh power density (272 mW cm -2 ), and an unprecedented 100 h stability at a high-current-density condition (100 mA cm -2 ), which is one of the best performances., (© 2023 Wiley‐VCH GmbH.)

Iron-nitrogen-carbon single atom catalyst (SAC) is regarded as one of the promising electrocatalysts for NO 3 - reduction reaction (NO 3 RR) to NH 3 due to its high activity and selectivity. However, synergistic effects of topological defects and FeN 4 active moiety in Fe-N-C SAC have rarely been investigated. By performing density functional theory (DFT) calculations, 13 defective graphene FeN 4 with 585, 484, and 5775 topological line defects are constructed, yielding 585-68-FeN 4 with optimal NO 3 RR catalytic activity, high selectivity, as well as robust anti-dissolution stability. The high NO 3 RR activity on 585-68-FeN 4 is well explained by the high valence state of Fe center as well as asymmetric charge distribution on FeN 4 moiety influenced by 5- and 8-member rings. This DFT work provides theoretical guidance for engineering NO 3 RR performance of iron-nitrogen-carbon catalysts by modulating periodic topological defects., (© 2023 Wiley-VCH GmbH.)

Electrochemical CO 2 reduction reaction (CO 2 RR) over Cu catalysts exhibits enormous potential for efficiently converting CO 2 to ethylene (C 2 H 4 ). However, achieving high C 2 H 4 selectivity remains a considerable challenge due to the propensity of Cu catalysts to undergo structural reconstruction during CO 2 RR. Herein, we report an in situ molecule modification strategy that involves tannic acid (TA) molecules adaptive regulating the reconstruction of a Cu-based material to a pathway that facilitates CO 2 reduction to C 2 H 4 products. An excellent Faraday efficiency (FE) of 63.6 % on C 2 H 4 with a current density of 497.2 mA cm -2 in flow cell was achieved, about 6.5 times higher than the pristine Cu catalyst which mainly produce CH 4 . The in situ X-ray absorption spectroscopy and Raman studies reveal that the hydroxyl group in TA stabilizes Cu δ+ during the CO 2 RR. Furthermore, theoretical calculations demonstrate that the Cu δ+ /Cu 0 interfaces lower the activation energy barrier for *CO dimerization, and hydroxyl species stabilize the *COH intermediate via hydrogen bonding, thereby promoting C 2 H 4 production. Such molecule engineering modulated electronic structure provides a promising strategy to achieve highly selective CO 2 reduction to value-added chemicals., (© 2023 Wiley-VCH GmbH.)

Electrochemical carbon dioxide reduction reaction (CO 2 RR) driven by renewable energy shows great promise in mitigating and potentially reversing the devastating effects of anthropogenic climate change and environmental degradation. The simultaneous synthesis of energy-dense chemicals can meet global energy demand while decoupling emissions from economic growth. However, the development of CO 2 RR technology faces challenges in catalyst discovery and device optimization that hinder their industrial implementation. In this contribution, a comprehensive overview of the current state of CO 2 RR research is provided, starting with the background and motivation for this technology, followed by the fundamentals and evaluated metrics. Then the underlying design principles of electrocatalysts are discussed, emphasizing their structure-performance correlations and advanced electrochemical assembly cells that can increase CO 2 RR selectivity and throughput. Finally, the review looks to the future and identifies opportunities for innovation in mechanism discovery, material screening strategies, and device assemblies to move toward a carbon-neutral society., (© 2023 Wiley-VCH GmbH.)

Controlling lithium (Li) electrocrystallization with preferred orientation is a promising strategy to realize highly reversible Li metal batteries (LMBs) but lack of facile regulation methods. Herein, we report a high-flux solid electrolyte interphase (SEI) strategy to direct (110) preferred Li deposition even on (200)-orientated Li substrate. Bravais rule and Curie-Wulff principle are expanded in Li electrocrystallization process to decouple the relationship between SEI engineering and preferred crystal orientation. Multi-spectroscopic techniques combined with dynamics analysis reveal that the high-flux CF 3 Si(CH 3 ) 3 (F 3 ) induced SEI (F 3 -SEI) with high LiF and -Si(CH 3 ) 3 contents can ingeniously accelerate Li + transport dynamics and ensure the sufficient Li + concentration below SEI to direct Li (110) orientation. The induced Li (110) can in turn further promote the surface migration of Li atoms to avoid tip aggregation, resulting in a planar, dendrite-free morphology of Li. As a result, our F 3 -SEI enables ultra-long stability of Li||Li symmetrical cells for more than 336 days. Furthermore, F 3 -SEI modified Li can significantly enhance the cycle life of Li||LiFePO 4 and Li||NCM811 coin and pouch full cells in practical conditions. Our crystallographic strategy for Li dendrite suppression paves a path to achieve reliable LMBs and may provide guidance for the preferred orientation of other metal crystals., (© 2023 Wiley-VCH GmbH.)

Direct conversion of methane to high-value-added transportable methanol is a great challenge, which requires high energy input to break the strong C-H bond. Developing efficient catalysts for methane oxidation to methanol under mild conditions is of vital importance. In this work, single transition metal atoms (TM=Fe, Co, Ni, Cu) anchored on black phosphorus (TM@BP) were studied as catalysts to assist the methane oxidation to methanol by means of first-principles calculations. The results indicate that Cu@BP exhibits an outstanding catalytic activity through the radical reaction pathways and the formation of the Cu-O active site is rate-determining with an energy barrier of 0.48 eV. Meanwhile, electronic structure calculations and dynamic simulations show that Cu@BP offers excellent thermal stability. Our calculations provide a new approach for the rational design of single atom catalysts for methane oxidation to methanol., (© 2023 Wiley-VCH GmbH.)

The low electrical conductivity and the high surface defect density of the TiO 2 electron transport layer (ETL) limit the power conversion efficiency (PCE) of corresponding perovskite solar cells (PSCs). Here, the conductivity and defect modulation of the mesoporous TiO 2 (mp-TiO 2 ) ETL via oxygen vacancy (OV) management by the reduction and oxidation treatment are reported. Reduction treatment via reducing agent introduces abundant OVs into the TiO 2 nanocrystalline particles on the surface and at the subsurface. The following oxidation treatment via hydrogen peroxide removes the surface OVs while remains the subsurface OVs, resulting in stratified OVs. The stratified OVs improve the conductivity of TiO 2 ETL by increasing carrier donors and decrease nonradiative centers by reducing surface defects. Such synergy ensures the capability of mp-TiO 2 as the well-performed ETL with improved energy level alignment, suppressed interface recombination, enhanced carrier extraction, and transport. As a result, printable hole-conductor-free carbon-based mesoscopic PSCs based on the modulated mp-TiO 2 ETL demonstrate a highest reported PCE of 18.96%., (© 2023 Wiley-VCH GmbH.)

The development of highly efficient and cost-effective hydrogen evolution reaction (HER) catalysts is highly desirable to efficiently promote the HER process, especially under alkaline condition. Herein, a polyoxometalates-organic-complex-induced carbonization method is developed to construct MoO 2 /Mo 3 P/Mo 2 C triple-interface heterojunction encapsulated into nitrogen-doped carbon with urchin-like structure using ammonium phosphomolybdate and dopamine. Furthermore, the mass ratio of dopamine and ammonium phosphomolybdate is found critical for the successful formation of such triple-interface heterojunction. Theoretical calculation results demonstrate that such triple-interface heterojunctions possess thermodynamically favorable water dissociation Gibbs free energy (ΔG H2O ) of -1.28 eV and hydrogen adsorption Gibbs free energy (ΔG H* ) of -0.41 eV due to the synergistic effect of Mo 2 C and Mo 3 P as water dissociation site and H* adsorption/desorption sites during the HER process in comparison to the corresponding single components. Notably, the optimal heterostructures exhibit the highest HER activity with the low overpotential of 69 mV at the current density of 10 mA cm -2 and a small Tafel slope of 60.4 mV dec -1 as well as good long-term stability for 125 h. Such remarkable results have been theoretically and experimentally proven to be due to the synergistic effect between the unique heterostructures and the encapsulated nitrogen-doped carbon., (© 2023 Wiley-VCH GmbH.)

Due to the unique safety qualities, solid composite polymer electrolyte (SCPE) has achieved considerable attentions to fabricate high-energy-density lithium metal batteries, but its overall performance still has to be improved. Herein, a high lithium salt content poly(vinylidene fluoride) (PVDF)-based SCPE was developed, enhanced by hexagonal boron nitride (h-BN) nanosheets, presenting perfect electrochemical performance, fast ion transport, and efficient inhibition of lithium dendrite growth. The optimized SCPE (PVDF-L70-B5) could deliver high ionic conductivity (2.98×10 -4  S cm -1 ), ultra-high Li + ion transfer number (0.62), wide electrochemical stability window (5.24 V), and strong mechanical strength (3.45 MPa) at room temperature. Density functional theory calculation further confirmed that the presence of h-BN could promote the dissociation of bis(trifluoromethanesulfonyl)imide lithium (LiTFSI) and the rapid transfer of Li + ions. As a result, the assembled symmetric Li/Li battery and asymmetric Li/LiFePO 4 battery using PVDF-L70-B5 SCPEs both exhibited high reversible capacity, long-term cycle stability, and high-rate performance when cycled at 60 or 30 °C. The designed SCPEs will open up a new route to synthesize solid-state lithium batteries with high energy density and high safety., (© 2022 Wiley-VCH GmbH.)

The electrocatalytic carbon dioxide reduction reaction (CO 2 RR) to value-added chemical products is an effective strategy for both greenhouse effect mitigation and high-density energy storage. However, controllable manipulation of the oxidation state and porous structure of Cu-carbon based catalysts to achieve high selectivity and current density for a particular product remains very challenging. Herein, a strategy derived from Cu-based metal-organic frameworks (MOFs) for the synthesis of controllable oxidation states and porous structure of Cu-carbon (Cu-pC, Cu 2 O-pC, and Cu 2 O/Cu-pC) is demonstrated. By regulating oxygen partial pressure during the annealing process, the valence state of the Cu and mesoporous structures of surrounding carbon are changed, leads to the different selectivity of products. Cu 2 O/CuO-pC with the higher oxidation state exhibits FE C2H4 of 65.12% and a partial current density of -578 mA cm -2 , while the Cu 2 O-pC shows the FE CH4 over 55% and a partial current density exceeding -438 mA cm -2 . Experimental and theoretical studies indicate that porous carbon-coated Cu 2 O structures favor the CH 4 pathway and inhibit the hydrogen evolution reaction. This work provides an effective strategy for exploring the influence of the various valence states of Cu and mesoporous carbon structures on the selectivity of CH 4 and C 2 H 4 products in CO 2 RR., (© 2022 Wiley-VCH GmbH.)

The planar SnO 2 electron transport layer (ETL) has contributed to the reported power conversion efficiency (PCE) record of perovskite solar cells (PSCs), while the high-temperature mesoporous SnO 2 ETL (mp-SnO 2 ) brings poor device performance. Herein, we report the application of mp-SnO 2 for efficient printable PSCs via oxygen vacancy (OV) management by introducing magnesium (Mg) into the paste. We find that high-temperature annealing suppresses self-doping of SnO 2 by reducing OVs. The introduced Mg occupies both the Sn site and interstitial site of SnO 2 and promotes the formation of OVs. Lattice Mg tends to induce neutral OVs and interstitial Mg could promote the ionization of neutral OVs for self-doping. The synergy effect on OVs increases the carrier density and upshifts the Fermi level energy of mp-SnO 2 , ensuring its capability as the well-performed ETL with trap-less charge transport and suppressed surface recombination for dramatic improved device PCE from 6.62 % to 17.25 %., (© 2022 Wiley-VCH GmbH.)

Ca-ion batteries (CIBs) have been considered a promising candidate for the next-generation energy storage technology owing to the abundant calcium element and the low reduction potential of Ca 2+ /Ca. However, the large size and divalent nature of Ca 2+ induce significant volume change and sluggish ion mobility in intercalation cathodes, leading to poor reversibly and low energy/power densities for CIBs. Herein, a polyanionic Na superionic conduction (NASICON)-typed Na-vacant Na 1 V 2 (PO 4 ) 2 F 3 (N 1 PVF 3 ) with sufficient interstitial spaces is reported as ultra-stable and high-energy Ca ion cathodes. The N 1 PVF 3 delivers exceptionally high Ca storage capacities of 110 and 65 mAh g -1 at 10 and 500 mA g -1 , respectively, and a record-long cyclability of 2000 cycles. More interestingly, by tailoring the fluorine content in N 1 PVF x (1 ≤ x ≤ 3), the high working potential of 3.5 V versus Ca 2+ /Ca is achievable. In conjunction with Ca metal anode and a compatible electrolyte, Ca metal batteries with N 1 VPF 3 cathodes are constructed, which deliver an initial energy density of 342 W h kg -1 , representing one of the highest values thus far reported for CIBs. Origins of the uncommonly stable and high-power capabilities for N 1 PVF 3 are elucidated as the small volume changes and low cation diffusion barriers among the cathodes., (© 2022 Wiley-VCH GmbH.)

The 1,3-conjugated diynes are an important class of chemical intermediates, and the selective crosscoupling of terminal alkynes is an efficient chemical process for manufacturing asymmetrical 1,3-conjugated diynes. However, it often occurs in homogenous conditions and costs a lot for reaction treatment. Herein, a copper catalyzed strategy is used to synthesize highly ordered mesoporous nitrogen-doped carbon material (OMNC), and the copper species is in situ transformed into the copper single-atom site with four nitrogen coordination (CuN 4 ). These features make the CuN 4 /OMNC catalyst efficient for selective oxidative crosscoupling of terminal alkynes, and a wide range of asymmetrical and symmetrical 1,3-diynes (26 examples) under mild conditions (40 °C) and low substrates ratio (1.3). Density functional theory (DFT) calculations reveal that the aryl-alkyl crosscoupling has the lowest energy barrier on the CuN 4 site, which can explain the high selectivity. In addition, the catalyst can be separated and reused by simply centrifugation or filtration. This work can open a facile avenue for constructing single-atom loaded mesoporous materials to bridge homogeneous and heterogeneous catalysis., (© 2021 Wiley-VCH GmbH.)

The ion intercalation behavior in 2D materials is widely applied in energy storage, electrocatalysis, and desalination. However, the detailed effect of ions on the performance, combining the influence of interlayer force and the change of solvent shell, is far less well understood. Here the solvated alkali metal ions with different sizes are intercalated into the lattice of 2D materials with different spacings (Ti 3 C 2 T x , δ-MnO 2 , and reduced graphene oxide) to construct the intercalation model related with sub-nanometer confined ions and solvent molecules to further understand the intercalation capacitance. Based on electrochemical methods and density functional theory calculation, the ions lose the electrostatic shielding solvent shell or shorten the distance between the layers, resulting in a significant increase in capacitance. It is found that the intercalation capacitance arises from the diffusion of solvated ions and is controlled by quantum and electrochemical capacitance for desolvated ions. This effect of solvation structure on performance can be applied in a variety of electrochemical interface studies and provides a new research view for energy storage mechanisms., (© 2021 Wiley-VCH GmbH.)

Uncontrolled dendrite formation in the high energy density of lithium (Li) metal batteries (LMBs) may pose serious safety risks. While numerous studies have attempted to protect separators, these proposed methods fail to effectively inhibit upward dendrite growth that punctures through the separator. Here, we introduce a novel "orientated-growth" strategy that transfers the main depositional interface to the anode/current collector interface from the anode/separator interface. We placed a layer of cellulose/graphene carbon composite aerogel (CCA) between the current collector and the anode (LCL-bottom). This layer works as a charge organizer that induces a high current density and encourages Li to deposit at the anode/current collector interface. Both in situ and ex situ images of the electrode demonstrate that the anode part of the cell has been flipped; with the newly deposited particles facing the current collector and the smooth surface facing the separator. The electrode in half and full cells showed outstanding cyclic stability and rate capability, with the LCL-bottom/LFP full cell capable of maintaining 94 % of its initial capacity after 1000 cycles., (© 2021 Wiley-VCH GmbH.)

Miniaturized energy storage device (MESD) is the core module in microscale electronic equipment, yet its electrochemical performance is far away from the actual requirements. The extensive research efforts have improved the performance of MESD via the fabrication techniques and material construction, while ignoring the expansion of optimization strategy in the combination of energy storage mechanism. Herein, the Prussian blue/Zn microbattery is reported with the regulation of lattice-water-adsorbed intercalated ion. The optimal charge transport of cathode is achieved via the optimization of 3D structure of microelectrode to maximize the electrochemical performance. Also, lattice-water-adsorbed ion storage mechanism is further investigated to guide the design of differential energy storage for cathode and anode. The Cu 3 (Fe(CN) 6 ) 2 /Zn microbattery, with K + inter/deintercalation in the cathode and Zn 2+ deplating/plating in the anode, displays high capacity (0.281 mAh cm -2 at 2.5 mA cm -2 ), rate performance (0.181 mAh cm -2 at 25 mA cm -2 ), and cycling stability (77.6% capacity retention after 1500 cycles) enhanced by Cu 2+ in the electrolyte. This highly efficient combination of fabrication process, active material, and multi-ion storage for microelectrode shows a high tolerance for optimization strategies, expanding the compatibility of optimization path for high-performance MESD., (© 2021 Wiley-VCH GmbH.)

Solar-driven vaporization is a sustainable solution to water and energy scarcity. However, most of the present evaporators are still suffering from inefficient utilization of converted thermal energy. Herein, a universal sandwich membrane strategy is demonstrated by confining the hierarchical porous carbon cells in two energy barriers to obtain a high-efficiency evaporator with a rapid water evaporation rate of 1.87 kg m -2 h -1 under 1 sun illumination, which is among the highest performance for carbon-based and wood-based evaporators. The significantly enhanced evaporation rate is mainly attributed to the inherently optimized porous evaporation mode derived from the hierarchical hollow structures of pollen carbon cells, and the synergistically regulated water transporting and thermal management performance of the sandwich membrane. Moreover, the constructed sandwich membrane also exhibits excellent self-regenerating performance in simulated seawater and high salinity water. The developed device can maintain an average evaporation rate of 4.3 L m -2 day -1 in a 25 day consecutive outdoor test., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lactams are privileged in bioactive natural products and pharmaceutical agents and widely featured in functional materials. This study presents a novel versatile approach to the direct synthesis of lactams from oxocarboxylic acids without catalyst or external hydrogen. The method involves the in situ release of formic acid from formamides induced by water to facilitate efficient cycloamination. Water also suppresses the formation of byproducts. This unconventional pathway is elucidated by a combination of model experiments and density functional theory calculations, whereby cyclic imines (5-methyl-3,4-dihydro-2-pyrrolone and its tautomeric structures) are found to be favorable intermediates toward lactam formation, in contrast to the conventional approach encompassing cascade reductive amination and cyclization. This sustainable and simple protocol is broadly applicable for the efficient production of various N-unsubstituted and N-substituted lactams., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The utilization of 5-(hydroxymethyl)furfural (HMF) for the large-scale production of essential chemicals has been largely limited by the formation of solid humin as a byproduct, which prevents the operation of stepwise batch-type and continuous flow-type processes. The reaction of HMF with 1,3-propanediol produces an HMF acetal derivative that exhibits excellent thermal stability. Aerobic oxidation of the HMF acetal with a CeO 2 -supported Au catalyst and Na 2 CO 3 in water gives a 90-95 % yield of furan 2,5-dicarboxylic acid, an increasingly important commodity chemical for the biorenewables industry, from concentrated solutions (10-20 wt %) without humin formation. The six-membered acetal ring suppresses thermal decomposition and self-polymerization of HMF in concentrated solutions. Kinetic studies supported by DFT calculations identify two crucial steps in the reaction mechanism, that is, the partial hydrolysis of the acetal into 5-formyl-2-furan carboxylic acid involving OH - and Lewis acid sites on CeO 2 , and subsequent oxidative dehydrogenation of the in situ generated hemiacetal involving Au nanoparticles. These results represent a significant advance over the current state of the art, overcoming an inherent limitation of the oxidation of HMF to an important monomer for biopolymer production., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)