Multistep Reaction Research Articles

Overcoming Energy-Scaling Barriers: Efficient Ammonia Electrosynthesis on High-Entropy Alloy Catalysts.

Electrochemically converting nitrate (NO3 -) to value-added ammonia (NH3) is a complex process involving an eight-electron transfer and numerous intermediates, presenting a significant challenge for optimization. A multi-elemental synergy strategy to regulate the local electronic structure at the atomic level is proposed, creating a broad adsorption energy landscape in high-entropy alloy (HEA) catalysts. This approach enables optimal adsorption and desorption of various intermediates, effectively overcoming energy-scaling limitations for efficient NH3 electrosynthesis. The HEA catalyst achieved a high Faradaic efficiency of 94.5±4.3% and a yield rate of 10.2±0.5mg h-1 mgcat -1. It also demonstrated remarkable stability over 250 h in an integrated three-chamber device, coupling electrocatalysis with an ammonia recovery unit for continuous NH3 collection. This work elucidates the catalytic mechanisms of multi-functional HEA systems and offers new perspectives for optimizing multi-step reactions by circumventing adsorption-energy scaling limitations.

Efficient amine-assisted CO2 hydrogenation to methanol co-catalyzed by metallic and oxidized sites within ruthenium clusters

Amine-assisted two-step CO2 hydrogenation is an efficient route for methanol production. To maximize the overall catalytic performance, both the N-formylation of amine with CO2 (i.e., first step) and the subsequent amide hydrogenation (i.e., second step) are required to be optimized. Herein, a class of Al2O3-supported Ru catalysts, featuring multiple activated Ru species (i.e., metallic and oxidized Ru), are rationally fabricated. Density functional theory calculations suggest that metallic Ru forms are preferred for N-formylation step, whereas oxidized Ru species demonstrate enhanced amide hydrogenation activity. Thus, the optimal catalyst, containing unique Ru clusters with coexisting metallic and oxidized Ru species, efficiently synergize the conversion of CO2 into methanol with exceptional selectivity (>95%) in a one-pot two-step process. This work not only presents an advanced catalyst for CO2-based methanol production but also highlights the strategic design of catalysts with multiple active species for optimizing the catalytic performances of multistep reactions in the future.

Understanding the Ligand Influence in the Multistep Reaction of Diazoalkanes with Palladium Complexes Leading to Carbene-Aryl Coupling

Understanding the Ligand Influence in the Multistep Reaction of Diazoalkanes with Palladium Complexes Leading to Carbene-Aryl Coupling

Efficient synthesis of highly substituted benzoselenazole derivatives through the one-pot, multi-step Ullmann coupling reaction

In this research, the simple and efficient method for the synthesis of highly substituted benzoselenazole derivatives using the one-pot, multi-step Ullman coupling reaction of acyl isoselenocyanate-nitro compounds adducts and dihalobenzene in the vicinity of K2CO3 as a base, copper iodide, at room temperature, and in MeCN solvent has been done successfully. The use of simple and available raw materials, mild copper catalytic reaction conditions, easy purification with the help of solvent, and finally the synthesis of 16 new compounds from the benzoselenazoles family are notable features of this protocol.

General access to furan-substituted gem-difluoroalkenes enabled by PFTB-promoted cross-coupling of ene-yne-ketones and difluorocarbene.

Replacement of a carbonyl group with fluorinated bioisostere (e.g., CF2[double bond, length as m-dash]C) has been adopted as a key tactical strategy in drug design and development, which typically improves potency and modulates lipophilicity while maintaining biological activity. Consequently, new gem-difluoroalkenation reactions have undoubtedly accelerated this shift, and conceptually innovative practices would be of great benefit to medicinal chemists. Here we describe an expeditous protocol for the direct assembly of furan-substituted gem-difluoroalkenes via PFTB-promoted cross-coupling of ene-yne-ketones and difluorocarbene. In this multi-step tandem reaction process, the furan ring and the gem-difluorovinyl group are constructed simultaneously in an efficient manner. These products can serve as bioisosteres of the α-carbonyl furan core, which is an important scaffold present in natural products and drug candidates. The broad generality and practicality of this method for late-stage modification of bioactive molecules, gram-scale synthesis and versatile derivatisation of products has been described. Biological activity evaluation showed that the gem-difluoroalkene skeleton exhibited dramatic antitumor activity.

Complete kinetic and photochemical characterization of the multi-step photochromic reaction of donor-acceptor Stenhouse adducts.

Donor-acceptor Stenhouse adducts (DASA) are negative photochromic compounds exhibiting a multi-step photoisomerization mechanism. Previous studies have described a first photoactivated step, followed by a thermally controlled one. This study emphasizes the key role of the intermediate species, using high-rate acquisition photokinetic absorption spectroscopy. We have investigated the multi-step processes at different temperatures and irradiation power values. For the first time, we have combined our experimental setup with a three-species photokinetic model to determine the kinetic constants and quantum yields of each step of a DASA compound. Finally, we have identified the key role of the intermediate species, showing that double irradiation experiments allow the tuning of the photochromic reaction.

Improved Methods for the Synthesis of B10H14 and N-Heterocycle-Coordinated B9H13 (N-Het·B9H13).

Improved methods for the synthesis of B10H14 and a series of N-heterocycle-coordinated B9H13 complexes (N-Het·B9H13) have been developed with readily obtained KB11H14 as the starting material. Oxidation of KB11H14 could provide B10H14 in over 90% yield. Then, the N-Het·B9H13 complexes were prepared from the as-synthesized B10H14 through in situ multistep reactions by reacting with NaH, N-heterocycles, and dilute hydrochloric acid. Among these N-Het·B9H13 complexes, 4-(triphenylvinyl)pyridine-coordinated B9H13 (1k) exhibits a significant aggregation-induced emission (AIE) effect in a THF/H2O mixed solution, and 8-aminoisoquinoline-coordinated B9H13 (2p) exhibits a positive solvatochromism phenomenon. These improved methods provide new approaches to synthesizing B10H14 and N-Het·B9H13 complexes with potential applications in luminescent materials.

Synthesis, Characterization, Docking and In Silico Pharmacokinetics Study of New Triazole Derivatives as TDP1 Enzyme Inhibitor Compounds

Numerous research groups across the globe have been dedicatedly studying the mechanism involved in carcinogenesis and cancer progression focusing on developing various strategies for the prevention and treatment of cancer. Chemotherapy is a treatment used for the whole body to fight recurrent tumors using conventional anticancer drugs which can be made more effective by using chemosensitizers, which can decrease the required dosage for treatment. TDP-1 inhibitors have the potential to enhance the effectiveness of topotecan by increasing the sensitivity of tumors to the drug, both in laboratory and living organism settings. A new triazole derivatives were synthesized starting from Naproxen and Vanillic acid through multisteps reactions. The final compounds and their intermediates were monitored by chromatography (TLC) and characterized by 1HNMR. The final compounds were docked against the target TDP1 enzyme. The docking analysis for the titled compounds 5A and 5B revealed better binding affinity values against (TDP1 enzyme) target site compared with the reference (co-crystallized) ligand as well as they showed good ADMET and in silico toxicity profile.

Rh(II)-Catalyzed Selective C(sp3)-H/C(sp2)-H Bonds Cascade Insertion to Construct [6-8-6] Benzo-Fused Scaffold.

The fused eight-membered carbocycles (EMCs) play vital roles in the medicinal and biological investigations of many natural products and marketed drugs. The traditional synthesis of [6-8-6] benzo-fused derivatives involves multistep reactions and low yields, making the development of a one-step synthesis method a more challenging work. Here, we present a novel strategy for one-step construction of [6-8-6] benzo-fused scaffold from propargyl diazoacetates substituted with benzyl-nitrogen heterocyclic ring via Rh(ll)-catalyzed carbene/alkyne metathesis (CAM) and selective C-H bond insertion. This method exhibits a specific substrate scope, simple operation, mild reaction conditions, and high atom efficiency. Mechanistically, the process involves sequential CAM, 1,3-H-shift, intramolecular nucleophilic attack, and selective C(sp3)-H/C(sp2)-H bonds cascade insertion. Notably, the unique spirocyclic zwitterionic intermediate generated in this sequence contributes to N-heterocycle migration and fused eight-membered carbocycle formation. Additionally, the C(sp3)-H bond insertion connected to the oxygen atom rather than the nitrogen atom has been unexpectedly confirmed with the assistance of the spirocyclic zwitterionic intermediate. Overall, our findings open up a new avenue for the construction of [6-8-6] benzo-fused scaffold.

Chemoenzymatic Synthesis Planning Guided by Reaction Type Score.

Thanks to the growing interest in computer-aided synthesis planning (CASP), a wide variety of retrosynthesis and retrobiosynthesis tools have been developed in the past decades. However, synthesis planning tools for multistep chemoenzymatic reactions are still rare despite the widespread use of enzymatic reactions in chemical synthesis. Herein, we report a reaction type score (RTscore)-guided chemoenzymatic synthesis planning (RTS-CESP) strategy. Briefly, the RTscore is trained using a text-based convolutional neural network (TextCNN) to distinguish synthesis reactions from decomposition reactions and evaluate synthesis efficiency. Once multiple chemical synthesis routes are generated by a retrosynthesis tool for a target molecule, RTscore is used to rank them and find the step(s) that can be replaced by enzymatic reactions to improve synthesis efficiency. As proof of concept, RTS-CESP was applied to 10 molecules with known chemoenzymatic synthesis routes in the literature and was able to predict all of them with six being the top-ranked routes. Moreover, RTS-CESP was employed for 1000 molecules in the boutique database and was able to predict the chemoenzymatic synthesis routes for 554 molecules, outperforming ASKCOS, a state-of-the-art chemoenzymatic synthesis planning tool. Finally, RTS-CESP was used to design a new chemoenzymatic synthesis route for the FDA-approved drug Alclofenac, which was shorter than the literature-reported route and has been experimentally validated.

Recent Progress in Cobalt‐Based Electrocatalysts for Efficient Electrochemical Nitrate Reduction Reaction

AbstractElectrochemical nitrate reduction reaction (NO3−RR) provides a sustainable and efficient way to producing ammonia at ambient condition and denitrifying wastewater. However, NO3−RR is still confronted with some barriers at present, because of the sluggish reaction kinetics and competitive hydrogen evolution reaction (HER). Particularly, it requires highly robust and selective electrocatalysts, which steers the complex multistep reactions toward NO3−RR process. Among the various electrocatalysts, Co‐based electrocatalysts demonstrate a rapid reaction kinetics, steady catalytic performance, and suppressive impact on HER for NO3−RR, attracting more attention. In this review, it is focused on Cobalt‐based electrocatalysts design for NO3−RR and the corresponding design strategies are summarized. In detail, these can be concisely classified into five categories, including the Co‐based oxides and hydroxides, alloys, metal, and heteroatom‐doped materials, metal organic frameworks and derivatives. Each category is extensively discussed, with its design concepts and ideas clearly conveyed through appropriate illustrations and figures. Finally, the scientific and technological challenges as well as promising constructing strategies for NO3−RR system in the future are discussed. It is expected that this review can provide valuable insights and guidance into rational design of Co‐based electrocatalysts for NO3−RR, ultimately advancing their applications to industrial scenario with high current density, stability, and energy efficiency.

Deposition Contribution Rates and Simulation Model Refinement for Polysilicon Films Deposited by Large-Sized Tubular Low-Pressure Chemical Vapor Deposition Reactors.

Tunnel oxide passivating contact cells have become the mainstream form of high-performance photovoltaic cells; however, the key factor restricting the further improvement of tunnel oxide passivating contact cell performance lies in the deposition process technology of high-quality polysilicon films. The experimental optimization cost for the deposition of large-sized polysilicon films in low-pressure chemical vapor deposition reactors is enormous when conducted in the temperature range of 800-950 K; hence, the necessity to develop effective computer simulation models becomes urgent. In recent years, our research group has conducted two-dimensional simulation research on large-sized, low-pressure chemical vapor deposition. This article focuses on analyzing the influence of gas-phase chemical reactions on the contribution rate of polysilicon film deposition under a mixed atmosphere of H2 and SiH4. The findings indicate that when using SiH4 as the precursor reactants with a gas pressure not exceeding 100 Pa, SiH4 contributes more than 99.6% to the deposition of polysilicon films, while the contribution rate of intermediates from chemical reactions to film deposition is less than 0.5% with 860-900 K. The influence of temperature on the contribution rate of gas-phase intermediates is negligible. It is found that simulating complex multi-step chemical reactions is highly resource-intensive, making it difficult to achieve the three-dimensional simulations of large-sized tubular LPCVD reactors. Based on the in-depth analysis of the mechanism and simulation results, a simplified model neglecting the complex multi-step chemical reaction process has been proposed. Through employing this refined and simplified model, the two-dimensional simulation of the polysilicon thin films deposition process in the large-sized tubular low pressure chemical vapor deposition reactor will become more effective and resource efficient.

Permeability-Engineered Compartmentalization System Promises Next-Generation Single-Cell Analysis.

Single-cell analysis, including sequencing, imaging, and biochemical assays, has become a fundamental strategy in biomedical research. Microplates, with their open system design, facilitate multistep reagent addition, subtraction, and buffer exchange, while their physically isolated wells prevent cross-contamination between biomolecules, establishing them as foundational compartmentalized platform for single-cell analysis. In contrast, water-in-oil droplets, produced by microfluidic systems, create nanoliter/picoliter-sized droplets that act as advanced compartmentalized platform. Although water-in-oil droplet systems offer significant advantages in single-cell analysis, their nearly complete isolation presents substantial limitations. This isolation impedes the development of ex vivo systems requiring material exchange, complicating complex multistep biochemical reactions and hindering the advancement of single-cell multiomics technologies and nonsequencing applications. Recent innovations in permeability-engineered compartmentalization systems, featuring unique materials and structures with controllable material exchange, promise to overcome these limitations. We discuss the latest advancements in permeability-engineered compartmentalization system, elucidates its underlying principles, and explores its potential applications in the field of single-cell analysis.

Total Synthesis of Euphorbialoid A.

Euphorbialoid A (1) belongs to the rare diterpenoid family of premyrsinanes and exhibits potent anti-inflammatory effects. The 5/7/6/3-membered carbocycle (ABCD-ring) of 1 contains 11 contiguous stereocenters and seven oxygen-containing functional groups. Moreover, four of the six hydroxy groups of 1 are concentrated in the southern sector and flanked by four structurally different acyl groups. The dense array of various functional groups with disparate reactivities on the tetracyclic ABCD-ring presents a daunting challenge for the chemical synthesis of 1. As a reflection of its formidable complexity, synthesis of 1 or any other premyrsinane diterpenoids has not yet been reported. Here, we devised a novel strategy comprising two stages and achieved the first total synthesis of 1 (35 steps as the longest linear sequence). In the first stage, the ABCD-ring was expeditiously assembled by integrating three powerful transformations: (1) Pt-doped TiO2-catalyzed radical coupling to attach a northern chain to a 6/3-membered CD-ring, (2) Pd-catalyzed decarboxylative asymmetric allylation to construct a quaternary carbon with a southern chain, and (3) a Co-mediated Pauson-Khand reaction to cyclize the two chains into the 5/7-membered AB-ring. In the second stage, three-dimensional structures of the ABCD-ring intermediates were utilized to stereoselectively fabricate the A-ring and site-selectively append the four different acyl groups. In the present total synthesis, we revealed the significance of orchestrating the multistep reaction sequence and incorporating cyclic protective groups. The overall strategy and tactics provide new insights into designing synthetic routes to premyrsinanes and densely oxygenated terpenoids decorated with diverse acyl groups.

Accuracy of kinetic parameters in multiple methods for separating multi-step thermal degradation reactions of biomass into single-step reactions

Accuracy of kinetic parameters in multiple methods for separating multi-step thermal degradation reactions of biomass into single-step reactions

A reduced methane pyrolysis mechanism for above-atmospheric pressure conditions

Methane pyrolysis has recently gained significant attention because of its potential to produce hydrogen without any CO2 emissions. Modeling a methane pyrolysis reactor requires a detailed multi-step reaction mechanism consisting of the full reaction pathway up to soot formation. Several models have been proposed in the literature; however, they have not been validated and calibrated to above-atmospheric pressure conditions. Due to the high number of parameters, adjusting the current models parameter set to high-pressure requires mechanism reduction and optimization. In this work, an existing methane pyrolysis mechanism consisting of 1516 reactions and 325 species was reduced using the directed relation graph with error propagation within a temperature and pressure range of 1000–1400 K and 0.1–4 atm. A skeletal mechanism consisting of 343 reactions and 60 species was obtained; resulting in a reaction and species reduction ratio of 4.4 and 5.3, respectively. The target species concentrations, namely CH4, H2, C2H2, C2H4, C2H6, α-C3H4, p-C3H4, were found to be in good agreement with the original mechanism predictions. Then, the rate parameters of the reduced mechanism were fitted against in-house experimental data in the temperature range of 892–1292 K and at a pressure of 4 atm to extend the model validity to above atmospheric pressures. The optimized model showed significant improvement in capturing the experimental data profiles compared to the reduced model predictions. A carbon element flux transfer was performed to identify the importance of additional pathways under high-pressure in aiding faster methane decomposition. The proposed model can be used for the accurate prediction of methane pyrolysis products at a wide range of temperatures and pressures.

Low-coordinated Fe−N3 single atom with rapid protonation for boosting oxygen reduction reactions

Accurately constructing the coordination environment of single-atom catalysts (SACs) is an available avenue to promote multistep tandem catalytic reactions, but challenging. Herein, we construct a Fe SAC with low-coordinated Fe − N3 configuration for efficient oxygen reduction reaction (ORR). Low-coordinated Fe − N3 successfully breaks the electron distribution symmetry of the Fe − N4 unit to optimize the adsorption strength of the reactive species on it. In situ characterization techniques directly observed the bond stretching and increased electron density of Fe − N3 configuration facilitates the dissociation of *OOH intermediates and protonation of *O, thus accelerating the four-electron reaction kinetics. Therefore, this designed Fe − N3 catalyst exhibits a mass activity of 619 A gmetal-1 at 0.85 V, nearly 39 times higher than commercial Pt/C (16 A gmetal-1), and a high four-electron selectivity of 99.1 %. Furthermore, the catalyst shows high power density (125.3 mW cm−2) in zinc-air batteries (ZABs), indicating its promising application potential. This work provides a new insight to construct well-defined SACs with coordination environment for efficient catalytic reactions.

Operando elucidation of hydrogen production mechanisms on sub-nanometric high-entropy metallenes

Precise morphological control and identification of structure-property relationships pose formidable challenges for high-entropy alloys, severely limiting their rational design and application in multistep and tandem reactions. Herein, we report the synthesis of sub-nanometric high-entropy metallenes with up to eight metallic elements via a one-pot wet-chemical approach. The PdRhMoFeMn high-entropy metallenes exhibit high electrocatalytic hydrogen evolution performances with 6, 23, and 26 mV overpotentials at −10 mA cm−2 in acidic, neutral, and alkaline media, respectively, and high stability. The electrochemical measurements, theoretical simulations, and operando X-ray absorption spectroscopy reveal the actual active sites along with their dynamics and synergistic mechanisms in various electrolytes. Specially, Mn sites have strong binding affinity to hydroxyl groups, which enhances the water dissociation process at Pd sites with low energy barrier while Rh sites with optimal hydrogen adsorption free energy accelerate hydride coupling, thereby markedly boosting its intrinsic ability for hydrogen production.

(Invited) Analysis of Electrochemical Reaction in Polysulfide-Insoluble Lithium Sulfur Battery with in-Situ Electrochemical Impedance Spectroscopic Method

Lithium-Sulfur battery (LiSB) has attracted attention as a new generation secondary battery. However, one of the major problems is dissolution of discharge products of lithium polysulfides (Li2S n ) that cause the self-discharge. Ionic liquids and super-concentrated electrolyte solution (SCES) have been attracting attention as a LiSB electrolyte due to its low solubility of the polysulfides. SCESs are electrolyte solutions which consist of only two or three times as much solvent as lithium salt. Watanabe and Dokko et al. [1] proposed polysulfides insoluble LiSBs using lithium-glyme based solvate ionic liquid (Li-Gn SIL) and sulfolane (SL)-based SCES. Various battery materials have been proposed for LiSBs; on the other hand, the discharge behavior strongly depends on the battery materials. Both the Li-Gn SIL and SL-based SCES are polysulfide-insoluble electrolytes, whereas the LiSB with the SL-based SCES has better battery performance than that with the Li-Gn SIL, implying that the discharge behavior is different between the LiSB with the SCES and LiSB with the SIL [1]. In this contribution, we carried out in situ electrochemical impedance spectroscopic measurement (EIS) [2,3] to reveal influence of different electrolytes on electrode reactions.A positive electrode slurry was obtained by mixing a sulfur S8, a Ketjen black (KB, EC600JD, Lion Corporation) and a carboxymethyl cellulose (CMC2200, Daicel) at a weight ratio of 60 : 30 : 10. The Slurry was spread on an Al foil to obtain a KB-S composite electrode. A negative electrode and a separator were used a lithium metal foil (Honjo Metal) and a glass separator (GA-55, Advantec), respectively. SL-based SCES and Li-Gn SIL are used as electrolyte solutions. The cells were assembled using three-electrode typed cell in an Ar-filled glove box. In situ EIS measurements were conducted at 0.025~0.1C-rate using an electrochemical measurement system (SP-150e, BioLogic). The DC current was superimposed with a small AC current adjusted so that the response voltage amplitude did not exceed 5~10 mV. The measurements were carried out in the frequency range from 500 kHz to 10 mHz. The measured impedance spectra during discharging/charging include the contribution of changes over time. Accordingly, the instantaneous impedance spectra at an arbitrary time were determined using the method to compensate for the changes over time [2,3].In discharge curves of the LiSB with Li-Gn SIL, a voltage drop was observed at DOD = 20−35% during discharge at a high C-rate (0.1C). This voltage drop did not appear in the discharge curve at a low C-rate (0.025C). The capacitive semicircle at 457 Hz appeared in the instantaneous impedance spectra of the LiSB during discharging. The diameter of this semicircle increased as the voltage dropped and the semicircle could be assigned to the charge transfer resistance of the lithium negative electrode. The charge transfer resistance of the negative electrode is related to the resistance of the Li+ ion dissolution/deposition reaction. During discharging at a high C-rate, the Li+ ion dissolution reaction could be suppressed.In the instantaneous impedance spectra of positive electrode in LiSB with SL-based SCES exhibited three capacitive semicircles and an inductive loop at DOD = 5%. Upon further discharging, the inductive loop changed into a capacitive semicircle. The Warburg impedance appeared at the end of the discharge period. This low-frequency impedance behavior was attributed to the Faradaic impedance due to elementary reactions on the electrode, such as intermediate reactions and redox species adsorption/desorption processes. This suggests that multi-step reactions occur in each DOD for the LiSB battery using SL based SCES.References1) A. Nakanishi et al., J. Phys. Chem. C, 123, 14229-14238 (2019).2) Z. B. Stoynov et al., J. Electroanal. Chem., 183, 133-144 (1985).3) M. Itagaki et al., J. Power Sources, 135, 255-261 (2004).

Ultrathin Pt Nanowire Network Monolayer for Oxygen Reduction Reaction

Owing to a rising energy demand with the increasing population and development of society, hydrogen fuel cells have attracted considerable attention in electrochemistry research. Compared with the hydrogen oxidation reaction at the anode, the oxygen reduction reaction (ORR) at the cathode exhibits more sluggish kinetics due to its multielectron, multistep reaction mechanism, which is the critical limiting step in hydrogen fuel cells. Therefore, developing catalysts with excellent performance for ORR is essential for developing hydrogen fuel cells. Pt nanomaterials represent the most widely explored ORR electrocatalysts for their high catalytic activities and stabilities in ORR.The morphology and surface structures of nanocatalysts are critical determinants of their catalytic performance, with both factors profoundly influenced by anisotropy. One-dimensional (1-D) and 2-D anisotropic Pt nanostructures demonstrate enhanced catalytic activity, due to structural anisotropy and larger surface area accessible for catalytic reactions. Owing to their high anisotropy and surface energy, one-dimensional (1-D) and 2-D anisotropic nanostructures are much more challenging to obtain, especially for the cubic lattice adopted by Pt with high symmetry, which leads to challenges in anisotropic growth from seed during colloidal synthesis. Anisotropic assembly of nanoscale building blocks can be an alternative strategy to synthesize anisotropic nanostructures, which may be guided by biomolecules due to their highly specific surface recognition properties.Here we report extensive macroscale 2-D platinum (Pt) nanowire network (NWN) sheets by a hierarchical self-assembly process with the assistance of biomolecular ligands. 1-D nanowires with a high density of grain boundaries are formed by the assembly of 1.9 nm 0-D Pt nanocrystals, and the interconnection of these 1-D nanowires forms the Pt NWN sheets with a centimeter-scale monolayer network structure extending into centimeter-scale size. The assembly of Pt nanocrystals occurs at the gas/liquid interfaces of the bubbles produced by sodium borohydride (NaBH4) during the synthesis process. The Pt NWN sheets are released at the gas/liquid surface after the rupture of these bubbles and merge into a centimeter-scale monolayer Pt NWN sheet. It is demonstrated that the monolayer Pt NWN sheet exhibits much-improved performance in oxygen reduction reaction (ORR), with 12.0 times and 21.2 times higher specific and mass activities than those of current state-of-the-art commercial Pt/C electrocatalysts. A 21.3 times greater mass activity than that of Pt/C is also observed in the Pt NWN sheet after 15,000 accelerated durability test cycles. The outstanding enhancement of the activity and stability in ORR can be attributed to the high electrochemical surface area and high density of defects formed during assembly.In summary, we developed an ultrathin monolayer Pt NWN sheet with abundant grain boundaries from the assembly of Pt nanocrystals with the assistance of biomolecules. The Pt NWN sheet has demonstrated outstanding catalytic activity and stability in ORR.