Adsorption and activation of small molecules on boron nitride catalysts.

Hexagonal boron nitride possesses a unique layered structure, high specific surface area and similar electronic properties as graphene, which makes it not only a promising catalyst support, but also a highly effective metal-free catalyst in the booming field of green chemistry. Reactions involving small molecules (e.g., oxygen, low carbon alkanes, nitrogen and carbon dioxide) have always been a hot topic in catalytic research, especially associated with the adsorption and activation regime of different forms of small molecules on catalysts. In this review, we have investigated the adsorption of different small molecules and the relevant activation mechanisms of four typical chemical bonds (OO, C-H, NN, CO) on hexagonal boron nitride. Recent progress on approaches adopted to enhance the activation capacity such as doping, defect engineering and heterostructuring are summarized, highlighting the potential applications of nonmetallic hexagonal boron nitride catalysts in various reactions. This comprehensive investigation offers a reference point for the enhanced mechanistic understanding and future design of effective and sustainable catalytic systems based on boron nitride.

Boosting CO2 electrocatalysis through electrical double layer regulations.

Interfacial investigation for fine-tuning microenvironment has recently emerged as a promising method to optimize the electrochemical CO2 reduction system. The electrical double layer located at the electrode-electrolyte interface presents a particularly significant impact on electrochemical reactions. However, its effect on the activity and selectivity of CO2 electrocatalysis remains poorly understood. Here, we utilized two-dimensional mica flakes, a material with a high dielectric constant, to modify the electrical double layer of Ag nanoparticles. This modification resulted in a significant enhancement of current densities for CO2 reduction and an impressive Faradaic efficiency of 98% for CO production. Our mechanistic investigations suggest that the enhancement of the electrical double layer capacitance through mica modification enriched local CO2 concentration near the reaction interface, thus facilitating CO2 electroreduction.

Acetamide Electrosynthesis from CO2 and Nitrite in Water.

Renewable electricity driven electrocatalytic CO2 reduction reaction (CO2 RR) is a promising solution to carbon neutralization, which mainly generate simple carbon products. It is of great importance to produce more valuable C-N chemicals from CO2 and nitrogen species. However, it is challenging to co-reduce CO2 and NO3 - /NO2 - to generate aldoxime an important intermediate in the electrocatalytic C-N coupling process. Herein, we report the successful electrochemical conversion of CO2 and NO2 - to acetamide for the first time over copper catalysts under alkaline condition through a gas diffusion electrode. Operando spectroelectrochemical characterizations and DFT calculations, suggest acetaldehyde and hydroxylamine identified as key intermediates undergo a nucleophilic addition reaction to produce acetaldoxime, which is then dehydrated to acetonitrile and followed by hydrolysis to give acetamide under highly local alkaline environment and electric field. Moreover, the above mechanism was successfully extended to the formation of phenylacetamide. This study provides a new strategy to synthesize highly valued amides from CO2 and wastewater.

Targeted metabolome and transcriptome analyses reveal changes in gibberellin and related cell wall-acting enzyme-encoding genes during stipe elongation in Flammulina filiformis.

Flammulina filiformis, a typical agaric fungus, is a widely cultivated and consumed edible mushroom. Elongation of its stipe (as the main edible part) is closely related to its yield and commercial traits; however, the endogenous hormones during stipe elongation and their regulatory mechanisms are not well understood. Gibberellin (GA) plays an important role in the regulation of plant growth, but little has been reported in macro fungi. In this study, we first treated F. filiformis stipes in the young stage with PBZ (an inhibitor of GA) and found that PBZ significantly inhibited elongation of the stipe. Then, we performed GA-targeted metabolome and transcriptome analyses of the stipe at both the young and elongation stages. A total of 13 types of GAs were detected in F. filiformis; the contents of ten of them, namely, GA3, GA4, GA8, GA14, GA19, GA20, GA24, GA34, GA44, and GA53, were significantly decreased, and the contents of three (GA5, GA9, and GA29) were significantly increased during stipe elongation. Transcriptome analysis showed that the genes in the terpenoid backbone biosynthesis pathway showed varying expression patterns: HMGS, HMGR, GPS, and FPPS were significantly upregulated, while CPS/KS had no significant difference in transcript level during stipe elongation. In total, 37 P450 genes were annotated to be involved in GA biosynthesis; eight of them were upregulated, twelve were downregulated, and the rest were not differentially expressed. In addition, four types of differentially expressed genes involved in stipe elongation were identified, including six signal transduction genes, five cell cycle-controlling genes, twelve cell wall-related enzymes and six transcription factors. The results identified the types and content of GAs and the expression patterns of their synthesis pathways during elongation in F. filiformis and revealed the molecular mechanisms by which GAs may affect the synthesis of cell wall components and the cell cycle of the stipe through the downstream action of cell wall-related enzymes, transcription factors, signal transduction and cell cycle control, thus regulating stipe elongation. This study is helpful for understanding the roles of GAs in stipe development in mushrooms and lays the foundation for the rational regulation of stipe length in agaric mushrooms during production.

Multiscale CO2 Electrocatalysis to C2+ Products: Reaction Mechanisms, Catalyst Design, and Device Fabrication.

Electrosynthesis of value-added chemicals, directly from CO2, could foster achievement of carbon neutral through an alternative electrical approach to the energy-intensive thermochemical industry for carbon utilization. Progress in this area, based on electrogeneration of multicarbon products through CO2 electroreduction, however, lags far behind that for C1 products. Reaction routes are complicated and kinetics are slow with scale up to the high levels required for commercialization, posing significant problems. In this review, we identify and summarize state-of-art progress in multicarbon synthesis with a multiscale perspective and discuss current hurdles to be resolved for multicarbon generation from CO2 reduction including atomistic mechanisms, nanoscale electrocatalysts, microscale electrodes, and macroscale electrolyzers with guidelines for future research. The review ends with a cross-scale perspective that links discrepancies between different approaches with extensions to performance and stability issues that arise from extensions to an industrial environment.

Electrosynthesis of ethylene glycol from C1 feedstocks in a flow electrolyzer.

Ethylene glycol is a widely utilized commodity chemical, the production of which accounts for over 46 million tons of CO2 emission annually. Here we report a paired electrocatalytic approach for ethylene glycol production from methanol. Carbon catalysts are effective in reducing formaldehyde into ethylene glycol with a 92% Faradaic efficiency, whereas Pt catalysts at the anode enable formaldehyde production through methanol partial oxidation with a 75% Faradaic efficiency. With a membrane-electrode assembly configuration, we show the feasibility of ethylene glycol electrosynthesis from methanol in a single electrolyzer. The electrolyzer operates a full cell voltage of 3.2 V at a current density of 100 mA cm-2, with a 60% reduction in energy consumption. Further investigations, using operando flow electrolyzer mass spectroscopy, isotopic labeling, and density functional theory (DFT) calculations, indicate that the desorption of a *CH2OH intermediate is the crucial step in determining the selectively towards ethylene glycol over methanol.

Scalable synthesis of Cu clusters for remarkable selectivity control of intermediates in consecutive hydrogenation.

Subnanometric Cu clusters that contain only a small number of atoms exhibit unique and, often, unexpected catalytic behaviors compared with Cu nanoparticles and single atoms. However, due to the high mobility of Cu species, scalable synthesis of stable Cu clusters is still a major challenge. Herein, we report a facile and practical approach for scalable synthesis of stable supported Cu cluster catalysts. This method involves the atomic diffusion of Cu from the supported Cu nanoparticles to CeO2 at a low temperature of 200 °C to form stable Cu clusters with tailored sizes. Strikingly, these Cu clusters exhibit high yield of intermediate product (95%) in consecutive hydrogenation reactions due to their balanced adsorption of the intermediate product and dissociation of H2. The scalable synthesis strategy reported here makes the stable Cu cluster catalysts one step closer to practical semi-hydrogenation applications.

Asymmetrical electrohydrogenation of CO2 to ethanol with copper-gold heterojunctions.

Copper is distinctive in electrocatalyzing reduction of CO2 into various energy-dense forms, but it often suffers from limited product selectivity including ethanol in competition with ethylene. Here, we describe systematically designed, bimetallic electrocatalysts based on copper/gold heterojunctions with a faradaic efficiency toward ethanol of 60% at currents in excess of 500 mA cm-2. In the modified catalyst, the ratio of ethanol to ethylene is enhanced by a factor of 200 compared to copper catalysts. Analysis by ATR-IR measurements under operating conditions, and by computational simulations, suggests that reduction of CO2 at the copper/gold heterojunction is dominated by generation of the intermediate OCCOH*. The latter is a key contributor in the overall, asymmetrical electrohydrogenation of CO2 giving ethanol rather than ethylene.

Electrothermal Water-Gas Shift Reaction at Room Temperature with a Silicomolybdate-Based Palladium Single-Atom Catalyst.

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H2 ) from methane (CH4 ), carbon dioxide (CO2 ), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H2 production provides an alternative strategy to obtain high-purity H2 streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd1 /CsSMA) and electrocatalytic H2 evolution. The two half-reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s-1 with turnover numbers above 40 000 mol CO 2 ${{_{{\rm CO}{_{2}}}}}$ molPd -1 achieving stable H2 production with a purity consistently exceeding 99.99 %.

Self-Supported Porous Carbon Nanofibers Decorated with Single Ni Atoms for Efficient CO2 Electroreduction.

Single-atom catalysts within M-N-C structures are efficient for electrochemical CO2 reduction. However, most of them are powdered and require a coating process to load on the electrode. Herein, we developed a facile approach to the synthesis of large-scale self-supported porous carbon nanofiber electrodes directly decorated with atomically dispersed nickel active sites using facile electrospinning, where poly(methyl methacrylate) was employed to tune well the distributions of pores located in carbon nanofibers. The above self-supported carbon nanofibers were applied as a gas diffusion electrode to achieve 94.3% CO Faraday efficiency and 170 mA cm-2 current density, which can be attributed to the effects of rich mesoporous structures favorable for adsorption and mass transfer of CO2 and single nickel catalysts effectively converting CO2 to CO. This work provides an efficient strategy to fabricate self-supported electrodes and may accelerate the progress toward industrial applications of single-atom catalysts in the field of CO2 electroreduction.

Effects of ß-1,6-Glucan Synthase Gene (FfGS6) Overexpression on Stress Response and Fruit Body Development in Flammulina filiformis.

ß-1, 6-glucan synthase is a key enzyme of ß-1, 6-glucan synthesis, which plays a vital role in the cell wall cross-linking of fungi. However, the role of the ß-1, 6-glucan synthase gene in the development of the fruiting body and the stress response of macrofungi is largely unknown. In this study, four overexpression transformants of the ß-1, 6-glucan synthase gene (FfGS6) were successfully obtained, and gene function was studied in Flammulina filiformis. The overexpression of FfGS6 can increase the width of mycelium cells and improve the tolerance ability under mechanical injury and oxidative stress. Moreover, FfGS6 gene expression fluctuated in up-regulation during the recovery process of mycelium injury but showed a negative correlation with H2O2 concentration. Fruiting body phenotype tests showed that mycelia's recovery ability after scratching improved when the FfGS6 gene was overexpressed. However, primordia formation and the stipe elongation ability were significantly inhibited. Our findings indicate that FfGS6 is involved in regulating mycelial cell morphology, the mycelial stress response, and fruit body development in F. filiformis.

Overexpression of heat shock protein 70 induces apoptosis of intestinal epithelial cells in heat-stressed pigs: A proteomics approach.

Heat stress (HS)-induced intestinal epithelial cell apoptosis may play a pivotal role in intestinal barrier dysfunction in animals. However, the underlying molecular mechanism by which HS induces apoptosis in intestinal epithelial cells is still poorly understood. Herein, a eukaryotic expression vector for an HSP70 gene was constructed and transfected into intestinal porcine epithelial cells (IPEC-J2). Afterward, functional proteomics approaches followed by liquid-chromatography-tandem mass spectrometry (LC-MS/MS) were used to identify interacting proteins. Analysis of HSP70 transfected IPEC-J2 cells revealed 246 differentially expressed proteins (DEPs), and functional annotation indicated that most DEPs were primarily related to ECM-receptor interaction, focal adhesion, and apoptosis. Furtherly, the apoptosis rate and expression levels of apoptosis-related proteins in HSP70 transfected IPEC-J2 cells were detected, we found that the expression of caspase-3, PARP, and Bax were increased, but Bcl-2 were decreased in transfected cells. Lastly, an in vitro and in vivo heat stress model were established to explore the role of HSP70 in intestinal epithelia cell apoptosis. The results of in vitrol study showed that HS-induced cellular apoptosis and increases of caspase-3, PARP, and Bax, but decreased of Bcl-2 in IPEC-J2 cells. In vivo study, the cell apoptosis were induced significantly in the duodenum, cecum, and colon of heat stressed pigs, and upregulation of HSP70 was also detected in colon tissues. Therefore, it has been shown that HSP70 plays a crucial role in heat stress-induced apoptosis and may provide new insights into the molecular mechanisms of epithelial cell apoptosis induced by heat stress in pigs.

Activation of the MoS2 Basal Plane to Enhance CO Hydrogenation to Methane Activity Through Increasing S Vacancies.

The active site of MoS2 is usually located at the edge of crystalline MoS2, which has a lower proportion than that from the basal plane, limiting the hydrogenation activity. Therefore, activating the basal plane of MoS2 is expected to greatly enhance the hydrogenation activity. Herein, we prepared a series of MoS2 catalysts by acidolysis of ammonium tetrathiomolybdate and subsequently pyrolyzing at high temperature with different atmospheres. Through analysis, we found that the prepared MoS2 catalysts were curved, which was different from commercial MoS2. Through X-ray diffraction, transmission electron microscopy, and Raman and X-ray photoelectron spectroscopy characterization, it was found that the MoS2 catalyst pyrolyzed under a N2 atmosphere had a larger number of S-vacancies than the MoS2 catalysts under a H2 atmosphere. In addition, temperature-programmed reduction results showed that the Mo-S bond energy was decreased with the increasing content of S-vacancies, which might be related to bending. Sulfur-resistant methanation results indicated that the curved MoS2 exhibited increased CO conversion with the increasing S vacancies. Furthermore, density functional theory calculation was used to simulate the generation of S vacancy and numbers of S vacancies. It was found that with the generation of S vacancy, three unsaturated coordination Mo atoms were exposed around one S vacancy and became new active sites, resulting in enhanced activity. What is more, the higher methanation activity was attributed not only from more S vacancies but also from the decreased activation energy for CO hydrogenation activation.

A Comprehensive Analysis of the Colonic Flora Diversity, Short Chain Fatty Acid Metabolism, Transcripts, and Biochemical Indexes in Heat-Stressed Pigs.

Heat stressed pigs show typical characteristics of inflammatory bowel disease (IBD). However, little is known about the pathogenesis of heat stress (HS)-induced IBD in pigs. In this study, we determined the effects of HS on colon morphology, intestinal microbiota diversity, transcriptome genes (transcripts), and short chain fatty acids (SCFAs) metabolism in pigs. In addition, the correlation among these parameters was analyzed by weighted gene co-expression network analysis. Results showed that the liver and kidney functions related to blood biochemical indexes were partially changed in pigs under HS. Furthermore, the levels of diamine oxidase and D-lactic acid were significantly increased, whereas the levels of secretory immunoglobulin A were decreased. The integrity of colonic tissue was damaged under HS, as bleeding, lymphatic infiltration, and villi injury were observed. The concentrations of SCFAs in the colon, such as acetic acid and butyric acid, were decreased significantly. In addition, the composition of colon microbiota, such as decrease in Lactobacillus johnsonii, Lactobacillus reuteri and increase in Clostridium sensu stricto 1 of day 7 and 14 while under HS. These changes were associated with changes in the concentration of SCFAs and biochemical indexes above mentioned. Differentially expressed genes were enriched in the nucleotide-binding oligomerization domain-like receptor signaling pathway, Th17 cell differentiation, and IBD pathway, which were also associated with the changes in SCFAs. Thus, the structure, diversity of intestinal microorganisms, and changes in the levels of SCFAs in colon of heat stressed pigs changed significantly, contributing to the activation of immune response and inflammatory signal pathways and causing abnormal physiological and biochemical indexes and intestinal mucosal damage. These results highlight the interconnections between intestinal microbiota, SCFAs, and immune response and their role in the pathogenesis of stress induced IBD therapy.

Chemodivergent Synthesis of One-Carbon-Extended Alcohols via Copper-Catalyzed Hydroxymethylation of Alkynes with Formic Acid.

The development of selective catalytic reactions that utilize easily available reagents for the efficient synthesis of alcohols is a long-standing goal of chemical research. Here an intriguing strategy for the chemodivergent copper-catalyzed hydroxymethylation of alkynes with formic acid and hydrosilane has been developed. By simply tuning the amount of formic acid and reaction temperature, distinct one-carbon-extended primary alcohols, that is, allylic alcohols and ß-branched alkyl alcohols, were produced with high levels of Z/E-, regio-, and enantioselectivity.

Electrochemical reduction of acetonitrile to ethylamine.

Electrifying chemical manufacturing using renewable energy is an attractive approach to reduce the dependence on fossil energy sources in chemical industries. Primary amines are important organic building blocks; however, the synthesis is often hindered by the poor selectivity because of the formation of secondary and tertiary amine byproducts. Herein, we report an electrocatalytic route to produce ethylamine selectively through an electroreduction of acetonitrile at ambient temperature and pressure. Among all the electrocatalysts, Cu nanoparticles exhibit the highest ethylamine Faradaic efficiency (~96%) at -0.29 V versus reversible hydrogen electrode. Under optimal conditions, we achieve an ethylamine partial current density of 846 mA cm-2. A 20-hour stable performance is demonstrated on Cu at 100 mA cm-2 with an 86% ethylamine Faradaic efficiency. Moreover, the reaction mechanism is investigated by computational study, which suggests the high ethylamine selectivity on Cu is due to the moderate binding affinity for the reaction intermediates.

Copper-Catalyzed and Proton-Directed Selective Hydroxymethylation of Alkynes with CO2.

An intriguing strategy for copper-catalyzed hydroxymethylation of alkynes with CO2 and hydrosilane was developed. Switched on/off a proton source, for example, t BuOH, direct hydroxymethylation and reductive hydroxymethylation could be triggered selectively, delivering a series of allylic alcohols and homobenzylic alcohols, respectively, with high levels of Z/E, regio- and enantioselectivity. Such a selective synthesis is attributed to the differences in response of vinylcopper intermediate to proton and CO2 . The protonation of vinylcopper species is demonstrated to be prior to hydroxymethylation, thus allowing a diversion from direct alkyne hydroxymethylation to reductive hydroxymethylation in the presence of suitable proton.

Template-induced Al distribution in MOR and enhanced activity in dimethyl ether carbonylation.

As the activity of dimethyl ether (DME) carbonylation over mordenite proportionally correlates with the Brønsted acid sites (BAS) in 8-membered ring (8-MR), enhancing the concentration of BAS in the 8-MR of MOR is important to improve the efficiency of the reaction. Herein, we report that the distribution of the BAS in the zeolite catalyst H-MOR can be altered by the synthesis of H-MOR with different cyclic amine structure-directing templates, several of which have not been reported previously for MOR synthesis. By combining FTIR, ICP, TG analysis and DFT calculations, it is verified that the strength of the interaction between amine or sodium cations and [AlO4]- in the zeolite framework plays a decisive role in Al distribution, owing to the competitive effect between Na+ and the cyclic amine compensating negative charges from the framework [AlO4]-. Quantitative analysis of the BAS in the 12-MR and 8-MR identifies the optimum template for maximizing the BAS in the 8-MR. It is shown that the enhanced activity of the H-MOR for the DME carbonylation to methyl acetate correlates with the increase in the BAS in the 8-MR. Our finding thus provides a facile strategy to direct Al location within different channels of the zeolite, which must benefit spatially confined reaction systems.

Morphology-Dependent Catalytic Performance of Mordenite in Carbonylation of Dimethyl Ether: Enhanced Activity with High c/b Ratio.

The morphology of zeolite often plays an important role in catalytic performance. Controllable synthesis of zeolite with special morphology and elucidating the structure-performance relationship of microporous zeolite are significant to its application. In this work, rod-assembled H-MOR with a controllable c/b ratio was successfully fabricated via template-free hydrothermal methods. NH3 adsorption IR and pyridine-adsorbed IR were employed to quantify the amount of acid sites in 8-MR and 12-MR of MOR. By excluding the influence of acidic properties on activity, the rate of methyl acetate formation via dimethyl ether carbonylation has been proved proportionally dependent on c/b ratio. Pressure-composition-temperature measurements revealed that the reactant, CO, readily enriches in the longer channels in the c-axis direction, resulting in an enhanced methyl acetate formation. Meanwhile, a higher concentration of CO in channels as well as severer diffusion limitation in the H-MOR with a higher c/b ratio results in a faster deactivation rate.

Preferential synthesis of ethanol from syngas via dimethyl oxalate hydrogenation over an integrated catalyst.

An integrated catalyst that contains Fe5C2 and CuZnO-SiO2 with a dual-bed configuration was designed for the preferential synthesis of ethanol via dimethyl oxalate hydrogenation. The cooperation of the two catalyst components remarkably inhibited the formation of various byproducts, resulting in a significantly high ethanol yield of about 98%.