Accelerated discovery of CO2 electrocatalysts using active machine learning.

The rapid increase in global energy demand and the need to replace carbon dioxide (CO2)-emitting fossil fuels with renewable sources have driven interest in chemical storage of intermittent solar and wind energy1,2. Particularly attractive is the electrochemical reduction of CO2 to chemical feedstocks, which uses both CO2 and renewable energy3-8. Copper has been the predominant electrocatalyst for this reaction when aiming for more valuable multi-carbon products9-16, and process improvements have been particularly notable when targeting ethylene. However, the energy efficiency and productivity (current density) achieved so far still fall below the values required to produce ethylene at cost-competitive prices. Here we describe Cu-Al electrocatalysts, identified using density functional theory calculations in combination with active machine learning, that efficiently reduce CO2 to ethylene with the highest Faradaic efficiency reported so far. This Faradaic efficiency of over 80 per cent (compared to about 66 per cent for pure Cu) is achieved at a current density of 400 milliamperes per square centimetre (at 1.5 volts versus a reversible hydrogen electrode) and a cathodic-side (half-cell) ethylene power conversion efficiency of 55 ± 2 per cent at 150 milliamperes per square centimetre. We perform computational studies that suggest that the Cu-Al alloys provide multiple sites and surface orientations with near-optimal CO binding for both efficient and selective CO2 reduction17. Furthermore, in situ X-ray absorption measurements reveal that Cu and Al enable a favourable Cu coordination environment that enhances C-C dimerization. These findings illustrate the value of computation and machine learning in guiding the experimental exploration of multi-metallic systems that go beyond the limitations of conventional single-metal electrocatalysts.

Bipyridine-Confined Silver Single-Atom Catalysts Facilitate In-Plane C-O Coupling for Propylene Electrooxidation.

The electrooxidation of propylene presents a promising route for the production of 1,2-propylene glycol (PG) under ambient conditions. However, the C-O coupling process remains a challenge owing to the high energy barrier. In this work, we developed a highly efficient electrocatalyst of bipyridine-confined Ag single atoms on UiO-bpy substrates (Ag SAs/UiO-bpy), which exposed two in-plane coordination vacancies during reaction for the co-adsorption of key intermediates. Detailed structure and electronic property analyses demonstrate that CH3CHCH2OH* and *OH could stably co-adsorb in a square planar configuration, which then accelerates the charge transfer between them. The combination of stable co-adsorption and efficient charge transfer facilitates the C-O coupling process, thus significantly lowering its energy barrier. At 2.4 V versus a reversible hydrogen electrode, Ag SAs/UiO-bpy achieved a record-high activity of 61.9 gPG m-2 h-1. Our work not only presents a robust electrocatalyst but also advances a new perspective on catalyst design for propylene electrooxidation.

Discovery of novel oridonin sulfamide derivatives as potent NLRP3 inhibitors by a visible-light photocatalysis-enabled peripheral editing.

The progress of organicsyntheticmethod can promote late-stage lead compound modification and novel active compound discovery. Molecular editing technology in the field of organic synthesis, including peripheral and skeletal editing, facilitates rapid access to molecular diversity of a lead compound. Peripheral editing of CH bond activation is gradually used in lead optimization to afford novel active scaffolds and chemical space exploitation. To develop oridonin derivatives with high anti-inflammatory potency, novel oridonin sulfamides had been designed and synthesized by a scaffoldhopping strategy based on a visible-light photocatalysis peripheral editing. All novel compounds revealed measurable inhibition of IL-1ß and low cytotoxicity in THP-1 cells. The docking study indicated that the best active compound ZM640 was accommodated in thebinding site of NLRP3 with two hydrogen bond interaction. These preliminary results confirm that α, ß-unsaturated carbonyl of oridonin is not essential for NLRP3 inhibitory effect. This new oridonin scaffold has its potential to be further developed as a promising class of NLRP3 inhibitors.

Synthesis and Antibacterial Evaluation of Novel Psoralen Derivatives against Methicillin-Resistant Staphylococcus aureus (MRSA).

Today, the bacterial infections caused by multidrug-resistant pathogens seriously threaten human health. Thereby, there is an urgent need to discover antibacterial drugs with novel mechanism. Here, novel psoralen derivatives had been designed and synthesized by a scaffold hopping strategy. Among these targeted twenty-five compounds, compound ZM631 showed the best antibacterial activity against methicillin-resistant S. aureus (MRSA) with the low MIC of 1 µg/mL which is 2-fold more active than that of the positive drug gepotidacin. Molecular docking study revealed that compound ZM631 fitted well in the active pockets of bacterial S. aureus DNA gyrase and formed a key hydrogen bond binding with the residue ASP-1083. These findings demonstrated that the psoralen scaffold could serve as an antibacterial lead compound for further drug development against multidrug-resistant bacterial infections.

Achieving Efficient CO2 Electrolysis to CO by Local Coordination Manipulation of Nickel Single-Atom Catalysts.

Selective electroreduction of CO2 to C1 feed gas provides an attractive avenue to store intermittent renewable energy. However, most of the CO2-to-CO catalysts are designed from the perspective of structural reconstruction, and it is challenging to precisely design a meaningful confining microenvironment for active sites on the support. Herein, we report a local sulfur doping method to precisely tune the electronic structure of an isolated asymmetric nickel-nitrogen-sulfur motif (Ni1-NSC). Our Ni1-NSC catalyst presents >99% faradaic efficiency for CO2-to-CO under a high current density of -320 mA cm-2. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and differential electrochemical mass spectrometry indicated that the asymmetric sites show a significantly weaker binding strength of *CO and a lower kinetic overpotential for CO2-to-CO. Further theoretical analysis revealed that the enhanced CO2 reduction reaction performance of Ni1-NSC was mainly due to the effectively decreased intermediate activation energy.

Polyethylene Recycling Via Water Activation By Ball Milling.

Polyethylene (PE) is the most prevalent type of plastic waste and also the most challenging to depolymerize because of its inert carbon-carbon (C-C) bonds.[1] High temperature and noble metals are usually required for depolymerization.[2] To avoid using noble metals, costly reagents and harsh reaction conditions, it is worthwhile but challenging to explore new reaction pathways.[3] We report an unprecedented mechanochemical reaction of PE and water to result in shorter-chain alkanes, alkenes, alcohols, and ketones (Cn, where n ≲ 50), with above 80 % of starting carbon converted into these products, which could be a valuable feedstock for re-entering chemical value chains. This reaction is driven solely by ball milling, without heating and pressurizing. No costly catalysts are used. Instead, only earth-abundant Al2O3 was milled with reactants.

Discovery of Novel 3,11-Bispeptide Ester Arenobufagin Derivatives with Potential in Vivo Antitumor Activity and Reduced Cardiotoxicity.

Arenobufagin, one of the bufadienolides isolated from traditional Chinese medicine Chan'su, exhibits potent antitumor activity. However, serious toxicity and small therapeutic window limits its drug development. In the present study, to our knowledge, novel 3,11-bispeptide ester arenobufagin derivatives have been firstly designed and synthesized on the base of our previous discovery of active 3-monopeptide ester derivative. The in vitro antiproliferative activity evaluation revealed that the moiety at C3 and C11 hydroxy had an important influence on cytotoxic activity and selectivity. Compound ZM350 notably inhibited tumor growth by 58.8 % at a dose 10 mg/kg in an A549 nude mice xenograft model. Therefore, compound ZM350 also presented a concentration-dependent apoptosis induction and low inhibitory effect against both hERG potassium channel and Cav1.2 calcium channel. Our study suggests that novel 3,11-bispeptide ester derivatives will be a potential benefit to further antitumor agent development of arenobufagin.

Discovery and optimization of betulinic acid derivatives as novel potent CD73 inhibitors.

The vast research and clinical result have verified the success of cancer immunotherapy. However, there is also facing the enormous challenges such as lack of precise pre-clinical models, optimal combined therapy regimen and acquired resistance to immunotherapy. Adenosine is a potent immune-modulating molecule and overexpression of CD73 on tumor leads to the high concentration of adenosine. Blockade of the key adenosine-generating enzyme CD73 can be a promising strategy for cancer immunotherapy. Here, we report the discovery of betulinic acid as a novel CD73 inhibitor lead compound by a hit-based substructure search strategy. Subsequent optimization led to the discovery of betulinic acid carbamate derivative ZM514 with 5.2-fold increased potency compared to lead compound. Simultaneously, study has showed that compound ZM514 was not a cytotoxic agent while betulinic acid showed modest antiproliferative activity. The present result provides a valuable inhibitor against the promising immuno-oncology target for further development.

A Theory-Guided X-ray Absorption Spectroscopy Approach for Identifying Active Sites in Atomically Dispersed Transition-Metal Catalysts.

Atomically dispersed supported metal catalysts offer new properties and the benefits of maximized metal accessibility and utilization. The characterization of these materials, however, remains challenging. Using atomically dispersed platinum supported on crystalline MgO (chosen for its well-defined bonding sites) as a prototypical example, we demonstrate how systematic density functional theory calculations for assessing all the potentially stable platinum sites, combined with automated analysis of extended X-ray absorption fine structure (EXAFS) spectra, leads to unbiased identification of isolated, surface-enveloped platinum cations as the catalytic species for CO oxidation. The catalyst has been characterized by atomic-resolution imaging and EXAFS and high-energy resolution fluorescence detection X-ray absorption near edge spectroscopy. The proposed platinum sites are in agreement with experiment. This theory-guided workflow leads to rigorously determined structural models and provides a more detailed picture of the structure of the catalytically active site than what is currently possible with conventional EXAFS analyses. As this approach is efficient and agnostic to the metal, support, and catalytic reaction, we posit that it will be of broad interest to the materials characterization and catalysis communities.

Discovery of natural product ellagic acid as a potent CD73 and CD39 dual inhibitor.

The ATP-adenosine pathway has been recently identified as an attractive immune-oncology target and several drug candidates have been entered clinic trials. Inspired by the report of the first small-molecule CD73inhibitor AB680, we describe the discovery of natural product ellagic acid as a dual CD73 and CD39 inhibitor with an IC50 value of 1.85 ± 0.21 µM and 0.50 ± 0.22 µM, respectively. The result of cytotoxicity assays indicated that ellagic acid is a valuable lead compound with low cytotoxicity effect for immune therapy.

Design, Synthesis and Biological Activity of (20S,21S)-7-Cyclohexyl-21-fluorocamptothecin Carbamates as Potential Antitumor Agents.

(20S,21S)-7-Cyclohexyl-21-fluorocamptothecin was discovered by a fluorine drug design strategy with potent antitumor activity and increased metabolic stability. In continuous efforts to find novel antitumor agents derived from natural product camptothecin, 20-carbamates of the active compound (20S,21S)-7-cyclohexyl-21-fluorocamptothecin have been designed and synthesized. Among them, one compound with the diethylamino group showed greater antiproliferative activity than the other 20-carbamate derivatives. The following biological activity assays indicated that the above compound is a valuable lead compound with excellent Topo I inhibitory activity and solution stability.

Molybdenum Disulfide-Black Phosphorus Hybrid Nanosheets as a Superior Catalyst for Electrochemical Hydrogen Evolution.

Engineering electronic properties is a promising way to design nonprecious-metal or earth-abundant catalysts toward hydrogen evolution reaction (HER). Herein, we deposited catalytically active MoS2 flakes onto black phosphorus (BP) nanosheets to construct the MoS2-BP interfaces. In this case, electrons flew from BP to MoS2 in MoS2-BP nanosheets because of the higher Fermi level of BP than that of MoS2. MoS2-BP nanosheets exhibited remarkable HER performance with an overpotential of 85 mV at 10 mA cm-2. Due to the electron donation from BP to MoS2, the exchange current density of MoS2-BP reached 0.66 mA cm-2, which was 22 times higher than that of MoS2. In addition, both the consecutive cyclic voltammetry and potentiostatic tests revealed the outstanding electrocatalytic stability of MoS2-BP nanosheets. Our finding not only provides a superior HER catalyst, but also presents a straightforward strategy to design hybrid electrocatalysts.

Discovery of Sophoridine α-Aryl Propionamide Derivative ZM600 as a Novel Antihepatic Fibrosis Agent.

Hepatic stellate cells (HSCs) activation is a key event in the development of liver fibrosis, and blockage of the activation of HSCs has been shown to alleviate liver fibrosis. Sophoridine, a bioactive alkaloid found in many Chinese herbs, exhibits a broad spectrum of pharmacological effects, but its activities are not strong. In this study, a series of structurally modified derivatives of sophoridine were designed and synthesized. Among them, sophoridine α-aryl propionamide derivative ZM600 displayed a significant inhibitory effect on the activation of HSCs. The in vivo experiment demonstrated that ZM600 markedly ameliorated carbon tetrachloride (CCl4) and bile duct ligation (BDL)-induced liver fibrosis with a significant improvement of extracellular matrix deposition. Mechanism investigations revealed that ZM600 specifically inhibited the activation of NF-κB, PI-3K/AKT, and TGF-ß/Smads signaling pathways. These results suggest that ZM600 has a protective effect on liver fibrosis, which provides a new candidate for the treatment of liver fibrosis.

Direct synthesis of extra-heavy olefins from carbon monoxide and water.

Extra-heavy olefins (C12+=), feedstocks to synthesize a wide range of value-added products, are conventionally generated from fossil resources via energy-intensive wax cracking or multi-step processes. Fischer-Tropsch synthesis with sustainably obtained syngas as feed-in provides a potential way to produce C12+=, though there is a trade-off between enhancing C-C coupling and suppressing further hydrogenation of olefins. Herein, we achieve selective production of C12+= via the overall conversion of CO and water, denoted as Kölbel-Engelhardt synthesis (KES), in polyethylene glycol (PEG) over a mixture of Pt/Mo2N and Ru particles. KES provides a continuously high CO/H2 ratio, thermodynamically favoring chain propagation and olefin formation. PEG serves as a selective extraction agent to hinder hydrogenation of olefins. Under an optimal condition, the yield ratio of CO2 to hydrocarbons reaches the theoretical minimum, and the C12+= yield reaches its maximum of 1.79 mmol with a selectivity (among hydrocarbons) of as high as 40.4%.

Efficient solvent- and hydrogen-free upcycling of high-density polyethylene into separable cyclic hydrocarbons.

Plastic pollution is a planetary threat that has been exacerbated by the COVID-19 pandemic due to the surge in medical waste, personal protective equipment and takeaway packaging. A socially sustainable and economically viable method for plastic recycling should not use consumable materials such as co-reactants or solvents. Here we report that Ru nanoparticles on zeolitic HZSM-5 catalyse the solvent- and hydrogen-free upcycling of high-density polyethylene into a separable distribution of linear (C1 to C6) and cyclic (C7 to C15) hydrocarbons. The valuable monocyclic hydrocarbons accounted for 60.3 mol% of the total yield. Based on mechanistic studies, the dehydrogenation of polymer chains to form C=C bonds occurs on both Ru sites and acid sites in HZSM-5, whereas carbenium ions are generated on the acid sites via the protonation of the C=C bonds. Accordingly, optimizing the Ru and acid sites promoted the cyclization process, which requires the simultaneous existence of a C=C bond and a carbenium ion on a molecular chain at an appropriate distance, providing high activity and cyclic hydrocarbon selectivity.

Manipulating local coordination of copper single atom catalyst enables efficient CO2-to-CH4 conversion.

Electrochemical CO2 conversion to methane, powered by intermittent renewable electricity, provides an entrancing opportunity to both store renewable electric energy and utilize emitted CO2. Copper-based single atom catalysts are promising candidates to restrain C-C coupling, suggesting feasibility in further protonation of CO* to CHO* for methane production. In theoretical studies herein, we find that introducing boron atoms into the first coordination layer of Cu-N4 motif facilitates the binding of CO* and CHO* intermediates, which favors the generation of methane. Accordingly, we employ a co-doping strategy to fabricate B-doped Cu-Nx atomic configuration (Cu-NxBy), where Cu-N2B2 is resolved to be the dominant site. Compared with Cu-N4 motifs, as-synthesized B-doped Cu-Nx structure exhibits a superior performance towards methane production, showing a peak methane Faradaic efficiency of 73% at -1.46 V vs. RHE and a maximum methane partial current density of -462 mA cm-2 at -1.94 V vs. RHE. Extensional calculations utilizing two-dimensional reaction phase diagram analysis together with barrier calculation help to gain more insights into the reaction mechanism of Cu-N2B2 coordination structure.

Application of a fluorine strategy in the lead optimization of betulinic acid to the discovery of potent CD73 inhibitors.

The ecto-5'-nucleotidase (CD73) is an important enzyme in the adenosine pathway and catalyzes the extracellular hydrolysis of adenosine monophosphate (AMP) yielding adenosine which is involved in the inflammation and immunosuppression. Inhibitors of CD73 have potential as novel immunotherapy agents for the treatment of cancer and infection. In this study, we discovered a series of fluorinated betulinic acid derivatives as potent CD73 inhibitors by a fluorine scanning strategy. Among these, three compounds ZM522, ZM553 and ZM557 exhibited inhibitory activity with IC50 values of 0.56 uM, 0.74 uM and 0.47 uM, respectively. In addition, these compounds showed a 7-fold, 5-fold and 8-fold increase in activity compared to the positive control drug α, ß-methylene adenosine diphosphate (APCP) against the human CD73 enzyme. Two of these (ZM522 and ZM553) also exhibited effective interferon gamma (INF-γ) elevation and indicated the regulation of rescued T cell activation. Therefore, our study provides both a lead optimization strategy and potential compounds for further development of small molecule CD73 inhibitors.

Discovery of 3-peptide substituted arenobufagin derivatives as potent antitumor agents with low cardiotoxicity.

Active natural productscan be valuable lead compounds and numerous drugs derived from natural products have successfully entered the clinic. Arenobufagin, one of the important active components of toad venom, indicates significant antitumor activities with limited preclinical development for its strong cardiotoxicity. Ten 3-monopeptide substituted arenobufagin derivatives have been designed and synthesized. Antitumor activity and cardiotoxicity assays lead to the discovery of compound ZM226 as a potent antitumor agent with low cardiotoxicity. These findings suggest optimization of arenobufagin on position 3 maybe an efficacious strategy for the development of antitumor drug candidates derived from arenobufagin.

Stable, active CO2 reduction to formate via redox-modulated stabilization of active sites.

Electrochemical reduction of CO2 (CO2R) to formic acid upgrades waste CO2; however, up to now, chemical and structural changes to the electrocatalyst have often led to the deterioration of performance over time. Here, we find that alloying p-block elements with differing electronegativities modulates the redox potential of active sites and stabilizes them throughout extended CO2R operation. Active Sn-Bi/SnO2 surfaces formed in situ on homogeneously alloyed Bi0.1Sn crystals stabilize the CO2R-to-formate pathway over 2400 h (100 days) of continuous operation at a current density of 100 mA cm-2. This performance is accompanied by a Faradaic efficiency of 95% and an overpotential of ~ -0.65 V. Operating experimental studies as well as computational investigations show that the stabilized active sites offer near-optimal binding energy to the key formate intermediate *OCHO. Using a cation-exchange membrane electrode assembly device, we demonstrate the stable production of concentrated HCOO- solution (3.4 molar, 15 wt%) over 100 h.