Conversion Of Precursors Research Articles

Co-applying biochar and manganese ore can improve the formation and stability of humic acid during co-composting of sewage sludge and corn straw

This study examined the effects of corn straw biochar (CSB) and manganese ore (MO) on the abiotic formation and stability of humic acid (HA) during sewage sludge composting. Co-applying CSB and MO (106%) induced a higher increase in HA content of final compost product than those of no or single applications (32.6–85.1%). This positive change was achieved by promoting the conversion of humus precursors and fulvic acid to HA through abiotic pathway, respectively, in the early and later stages of composting. The co-application of CSB and MO also exhibited a higher capacity to improve HA stability than those of single applications. In sum, this study confirmed a clear synergistic effect of CSB and MO on improving the formation and stability of HA in compost product, which could further enhance the multi-benefits (e.g., carbon sequestration and soil quality improvement) of compost soil application.

Facile water-free synthesis of noble metal-containing hydrotalcites-derived materials and their application for hydrotreatment of anisole

A novel, solvent-free, atom-efficient, and environmentally friendly method for preparing nickel-based hydrotalcite (HT) materials containing group VIII metals was established. A series of nickel-based (NiRu, NiRh, NiIr, NiSn, NiFe, NiCo, NiIn, and NiAl) HT-type materials were successfully synthesized using a facile water-free solid-state grinding method. The precursor-gel obtained by solid-state grinding facilitates efficient hydrolysis of metal salts by the use of ammonium hydroxide and results in the formation of layered HT materials. The presence of layered HT structure was evident from the powder X-ray diffraction (XRD) analysis. The method provides the complete conversion of metal precursors into the corresponding HT materials in an atom-efficient manner. The developed nickel-based HT materials were highly efficient and reusable catalysts for the hydrotreatment of the lignin-derived model compound, anisole. Among the several catalysts prepared, the one based on nickel-ruthenium catalysts showed complete conversion of anisole with 86% selectivity toward cyclohexane under optimum reaction conditions. The presence of in-situ generated metallic nickel‒ruthenium species on the surface of the catalyst, as evident from XPS, TEM, and XRD analysis of the spent catalyst, was responsible for the observed superior catalytic activity.

Effect of Cold Stabilization Duration on Organic Acids and Aroma Compounds during Vitis vinifera L. cv. Riesling Wine Bottle Storage.

During the storage of wines in bottles, especially white wines, tartrate crystallization often occurs, which reduces the commercial value of the wines and therefore needs to be avoided by performing cold stabilization treatments before bottling. However, whether different cold treatment durations impact the quality of a wine’s aroma has not yet been of special concern. This research was conducted at an industrial scale to explore how cold treatments at −5.3 °C for 10 to 15 days impact the organic acids, aroma compounds, and sensory quality of Riesling dry white wines, and the variation was documented at the end of treatment, and at 6 and 12 months of bottle storage. The results showed that cold treatments significantly reduced tartaric acid concentrations and significantly affected the concentrations of most aroma components in the wines only after 12 months of bottle storage, including the main components of esters, norisoprenoids, terpenoids, and furfural. Moreover, the concentrations of some components showed an increasing trend with the bottle storage, especially 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), the characteristic volatile of Riesling wine, suggesting that an acidic condition resulting from cold treatment might facilitate the conversion of some aroma precursors into volatiles. In conclusion, cold stabilization treatments, within limits, can improve tartaric acid stability and could promote the conservation of aroma compounds during bottle storage without adversely affecting the aroma profile of the wines.

Combustion-assisted low-temperature solution process for high-performance SnO2 thin-film transistors

In this study, high-performance SnO2 thin-film transistors (TFTs) were fabricated at temperatures below 300 °C using the combustion-assisted sol-gel method. The internal energy induced by the exothermic reaction of the fuel and the oxidizer in the combustion precursors facilitates precursor conversion even at low processing temperatures, leading to the development of crystalline SnO2. Compared to the conventional solution process, it was confirmed that the precursor was converted to crystalline SnO2 at below 300 °C through thermogravimetric analysis, differential scanning calorimetry, and grazing incidence X-ray diffraction. In addition, X-ray photoelectron spectroscopy spectra indicate the formation of complete metal-oxygen-metal networks with an increase in the oxygen corresponding to the lattice, as well as a decrease in hydroxyl groups. As a result, compared with the conventional SnO2 TFTs, the field-effect mobility of combustion-assisted SnO2 TFTs increased significantly from 0.014 ± 0.01 to 2.43 ± 0.22 cm2/Vs at 250 °C (by ∼ 170 times) and from 0.38 ± 0.15 to 6.53 ± 0.41 cm2/Vs at 300 °C (by ∼ 17 times). Therefore, the combustion-assisted solution process is expected not only to realize fully low-cost solution-processed electronics by fabricating high-quality SnO2 at low temperatures, but also to be combined with plastic substrates to fabricate flexible electronics.

Transient expansion and myofibroblast conversion of adipogenic lineage precursors mediate bone marrow repair after radiation.

Radiation causes a collapse of bone marrow cells and elimination of microvasculature. To understand how bone marrow recovers after radiation, we focused on mesenchymal lineage cells that provide a supportive microenvironment for hematopoiesis and angiogenesis in bone. We recently discovered a nonproliferative subpopulation of marrow adipogenic lineage precursors (MALPs) that express adipogenic markers with no lipid accumulation. Single-cell transcriptomic analysis revealed that MALPs acquire proliferation and myofibroblast features shortly after radiation. Using an adipocyte-specific Adipoq-Cre, we validated that MALPs rapidly and transiently expanded at day 3 after radiation, coinciding with marrow vessel dilation and diminished marrow cellularity. Concurrently, MALPs lost most of their cell processes, became more elongated, and highly expressed myofibroblast-related genes. Radiation activated mTOR signaling in MALPs that is essential for their myofibroblast conversion and subsequent bone marrow recovery at day 14. Ablation of MALPs blocked the recovery of bone marrow vasculature and cellularity, including hematopoietic stem and progenitors. Moreover, VEGFa deficiency in MALPs delayed bone marrow recovery after radiation. Taken together, our research demonstrates a critical role of MALPs in mediating bone marrow repair after radiation injury and sheds light on a cellular target for treating marrow suppression after radiotherapy.

ZIF-8/GO sandwich composite membranes through a precursor conversion strategy for H2/CO2 separation

It is difficult to control the heterogeneous nucleation and growth of crystals on porous supports, the preparation of thin ZIF-8 membranes is still extremely challenging. Herein, a two-dimensional transformation strategy is demonstrated for constructing a ZIF-8/GO ‘sandwich’ composite membrane with a thickness of ∼0.9 μm, which was prepared from Zn-EG-AC (EG: ethylene glycol, AC: CH3COO-groups, abbreviated as ZnEG) on alumina hollow fiber support for the first time by precursor conversion method in 2-methylimidazole methanol solution. The effects of the amount of precursor, reaction time and membrane thickness on the membrane structure and H2/CO2 separation performance are explored. The sieving effect of ZIF-8 and the adsorption effect of 2-methylimidazole rings on CO2, as well as the strong interaction between GO and CO2 hinder the permeation of CO2 into the membrane, thus exhibiting a good H2/CO2 ideal separation selectivity of 30.8 with the H2 permeance of 1.36 × 10−7 mol·Pa−1·m−2·s−1 under the optimized preparation conditions. The separation factor of the equimolar H2/CO2 binary-mixture gases stabilizes to ∼25 after 30 h. This precursor conversion strategy is expected to be extended to other MOF/graphene oxide (GO) composite membrane systems.

A carlactonoic acid methyltransferase that contributes to the inhibition of shoot branching in Arabidopsis

SignificanceStrigolactones (SLs) are a group of apocarotenoid hormones, which regulates shoot branching and other diverse developmental processes in plants. The major bioactive form(s) of SLs as endogenous hormones has not yet been clarified. Here, we identify an Arabidopsis methyltransferase, CLAMT, responsible for the conversion of an inactive precursor to a biologically active SL that can interact with the SL receptor invitro. Reverse genetic analysis showed that this enzyme plays an essential role in inhibiting shoot branching. This mutant also contributed to specifying the SL-related metabolites that could move from root to shoot in grafting experiments. Our work has identified a key enzyme necessary for the production of the bioactive form(s) of SLs.

Aerosol formation pathways from aviation emissions

Aviation emissions are responsible for an estimated 24,000 premature mortalities annually and 3.5% of anthropogenic radiative forcing (RF). Emissions of nitrogen and sulfur oxides (NOx and SOx) contribute to these impacts. However, the relative contributions and mechanisms linking these emissions to formation and impacts of secondary aerosols (as opposed to direct aerosol emissions) have not been quantified, including how short-lived aerosol precursors at altitude can increase surface-level aerosol concentrations. We apply global chemistry transport modeling to identify and quantify the different chemical pathways to aerosol formation from aviation emissions, including the resulting impact on radiative forcing. We estimate a net aerosol radiative forcing of –8.3 mWm−2, of which –0.67 and –7.8 mWm−2 result from nitrate and sulfate aerosols respectively. We find that aviation NOx causes –1.7 mWm−2 through nitrate aerosol forcing but also –1.6 mWm−2 of sulfate aerosol forcing by promoting oxidation of SO2 to sulfate aerosol. This accounts for 21% of the total sulfate forcing, and oxidation of SO2 due to aviation NOx is responsible for 47% of the net aviation NOx attributable RF. Aviation NOx emissions in turn account for 41% of net aviation-aerosol-attributable RF (non-contrail). This is due to ozone-mediated oxidation of background sulfur and the ‘nitrate bounce-back’ effect, which reduces the net impact of sulfur emissions. The ozone-mediated mechanism also explains the ability of cruise aviation emissions to significantly affect surface aerosol concentrations. We find that aviation NOx emissions cause 72% of aviation-attributable, near-surface aerosol loading by mass, compared to 27% from aviation SOx emissions and less than 0.1% from direct emission of black carbon. We conclude that aviation NOx and SOx emissions are the dominant cause of aviation-attributable secondary inorganic aerosol radiative forcing, and that conversion of background aerosol precursors at all altitudes is amplified by enhanced production of aviation attributable oxidants at cruise altitudes.

Abiraterone switches castration-resistant prostate cancer dependency from adrenal androgens towards androgen receptor variants and glucocorticoid receptor signalling.

IntroductionCastration‐resistant prostate cancer (CRPC) remains dependent on androgen receptor (AR) signalling, which is largely driven by conversion of adrenal androgen precursors lasting after castration. Abiraterone, an inhibitor of the steroidogenic enzyme CYP17A1, has been demonstrated to reduce adrenal androgen synthesis and prolong CRPC patient survival. To study mechanisms of resistance to castration and abiraterone, we created coculture models using human prostate and adrenal tumours.Materials and MethodsCastration‐naïve and CRPC clones of VCaP were incubated with steroid substrates or cocultured with human adrenal cells (H295R) and treated with abiraterone or the antiandrogen enzalutamide. Male mice bearing VCaP xenografts with and without concurrent H295R xenografts were castrated and treated with placebo or abiraterone. Response was assessed by tumour growth and PSA release. Plasma and tumour steroid levels were assessed by LC/MS‐MS. Quantitative polymerase chain reaction determined steroidogenic enzyme, nuclear receptor and AR target gene expression.ResultsIn vitro, adrenal androgens induced castration‐naïve and CRPC cell growth, while precursors steroids for de novo synthesis did not. In a coculture system, abiraterone blocked H295R‐induced growth of VCaP cells. In vivo, H295R promoted castration‐resistant VCaP growth. Abiraterone only inhibited VCaP growth or PSA production in the presence of H295R. Plasma steroid levels demonstrated CYP17A1 inhibition by abiraterone, whilst CRPC tumour tissue steroid levels showed no evidence of de novo intratumoural androgen production. Castration‐resistant and abiraterone‐resistant VCaP tumours had increased levels of AR, AR variants and glucocorticoid receptor (GR) resulting in equal AR target gene expression levels compared to noncastrate tumours.ConclusionsIn our model, ligand‐dependent AR‐regulated regrowth of CRPC was predominantly supported via adrenal androgen precursor production while there was no evidence for intratumoural androgen synthesis. Abiraterone‐resistant tumours relied on AR overexpression, expression of ligand‐independent AR variants and GR signalling.

Physiological Aspects of Germination and Early Seedling Establishment of Pleurotus sajor-caju Glyceraldehyde-3-Phosphate Dehydrogenase Expressing Transgenic Rice in Saline Environment.

GPD encodes glyceraldehyde-3-phosphate dehydrogenase enzyme involved in sugar mobilization, particularly glycolysis and gluconeogenesis. The objective of this study was to determine physiological aspects of germination and early seedling establishment of PsGPD (Pleurotus sajor-caju glyceraldehyde-3-phosphate dehydrogenase) expressing transgenic rice (T5) against different salt concentrations. The T5 line that carried 2 copies of T-DNA and had the highest level of PsGPD expression was used in the investigation. Final germination percentage, amylase activity, reducing sugar accumulation, and chlorophyll biosynthesis were comparatively higher in PsGPD expressing transgenic rice against elevating saline conditions. A slow-paced conversion of porphyrin's precursors was seen through the matrix model and further elaborated by a graphical model. A sustained level of porphyrin was observed in PsGPD expressing transgenic rice. These data were concurrent with the relative gene expression and thermal imaging (thermography) of PsGPD expressing transgenic rice against salt stress. Morphological attributes also favored the salt tolerance exhibited by PsGPD-transformed rice.

Indium(II) Chloride as a Precursor in the Synthesis of Ternary (Ag-In-S) and Quaternary (Ag-In-Zn-S) Nanocrystals.

A new indium precursor, namely, indium(II) chloride, was tested as a precursor in the synthesis of ternary Ag–In–S and quaternary Ag–In–Zn–S nanocrystals. This new precursor, being in fact a dimer of Cl2In–InCl2 chemical structure, is significantly more reactive than InCl3, typically used in the preparation of these types of nanocrystals. This was evidenced by carrying out comparative syntheses under the same reaction conditions using these two indium precursors in combination with the same silver (AgNO3) and zinc (zinc stearate) precursors. In particular, the use of indium(II) chloride in combination with low concentrations of the zinc precursor yielded spherical-shaped (D = 3.7–6.2 nm) Ag–In–Zn–S nanocrystals, whereas for higher concentrations of this precursor, rodlike nanoparticles (L = 9–10 nm) were obtained. In all cases, the resulting nanocrystals were enriched in indium (In/Ag = 1.5–10.3). Enhanced indium precursor conversion and formation of anisotropic, longitudinal nanoparticles were closely related to the presence of thiocarboxylic acid type of ligands in the reaction mixture. These ligands were generated in situ and subsequently bound to surfacial In(III) cations in the growing nanocrystals. The use of the new precursor of enhanced reactivity facilitated precise tuning of the photoluminescence color of the resulting nanocrystals in the spectral range from ca. 730 to 530 nm with photoluminescence quantum yield (PLQY) varying from 20 to 40%. The fabricated Ag–In–S and Ag–In–Zn–S nanocrystals exhibited the longest, reported to date, photoluminescence lifetimes of ∼9.4 and ∼1.4 μs, respectively. It was also demonstrated for the first time that ternary (Ag–In–S) and quaternary (Ag–In–Zn–S) nanocrystals could be applied as efficient photocatalysts, active under visible light (green) illumination, in the reaction of aldehydes reduction to alcohols.

Synthesis of flexible Co nanowires from bulk precursors.

This work reports a method of producing flexible cobalt nanowires (NWs) directly from the chemical conversion of bulk precursors at room temperature. Chemical reduction of Li6CoCl8 produces a nanocomposite of Co and LiCl, of which the salt is subsequently removed. The dilute concentration of Co in the precursor combined with the anisotropic crystal structure of the hcp phase leads to 1D growth in the absence of any templates or additives. The Co NWs are shown to have high saturation magnetization (130.6 emu g−1). Our understanding of the NW formation mechanism points to new directions of scalable nanostructure generation.

7,8-Dihydroxyflavone alleviates apoptosis and inflammation induced by retinal ischemia-reperfusion injury via activating TrkB/Akt/NF-kB signaling pathway.

Retinal ischemia-reperfusion injury (RIRI) is of common occurrence in retinal and optic nerve diseases. The BDNF/TrkB signaling pathway has been examined to be neuroprotective in RIRI. In this study, we investigated the role of a potent selective TrkB agonist 7,8-dihydroxyfavone (DHF) in rat retinas with RIRI. Our results showed that RIRI inhibited the conversion of BDNF precursor (proBDNF) to mature BDNF (mBDNF) and increased the level of neuronal cell apoptosis. Compared with RIRI, DHF+RIRI reduced proBDNF level and at the same time increased mBDNF level. Moreover, DHF administration effectively activated TrkB signaling and and downstream Akt and Erk signaling pathways which increased nerve cell survival. The combined effects of mBDNF/proBDNF increase and TrkB signaling activation lead to reduction of apoptosis level and protection of retinas with RIRI. Moreover, it was also found that astrocytes labeled by GFAP were activated in RIRI and NF-kB mediated the increased expressions of inflammatory factors and these effects were partially reversed by DHF administration. Besides, we also used RNA sequencing to analyze the differently expressed genes (DEGs) and their enriched (Kyoto Encyclopedia of Genes and Genomes) KEGG pathways between Sham, RIRI, and DHF+RIRI. It was found that 1543 DEGs were differently expressed in RIRI and 619 DEGs were reversed in DHF+RIRI. The reversed DEGs were typically enriched in PI3K-Akt signaling pathway, Jak-STAT signaling pathway, NF-kB signaling pathway, and Apoptosis. To sum up, the DHF administration alleviated apoptosis and inflammation induced by RIRI via activating TrkB signaling pathway and may serve as a promising drug candidate for RIRI related ophthalmopathy.

Interaction between polyphenols and amyloids: from the view of prevention of protein misfolding disorders related diseases

Amyloid is the term usually used to describe a particular type of elongated, unbranched protein fibril with cross-<i>β</i>-sheet characteristics, formed through the ordered aggregation of peptides or denatured proteins. Amyloids show high association with many severe neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's diseases. Unfortunately, there are still no effective medical treatments to cure these neurodegenerative diseases, including the failure of pharmaceutical approaches with amyloids as the targets. Polyphenols, the major phytochemicals in fruits, vegetables, tea and coffee have many beneficial functional properties, such as antioxidant, antimicrobial and anticancer properties. Polyphenols can interact with proteins through non-covalent interactions, including hydrophobic interaction, hydrogen bonding and electrostatic interaction. Polyphenols can also covalently interact with proteins mainly via the interaction between quinones, the oxidized products of polyphenols, and the nucleophilic residues (thiol, amino, guanidine, or imidazole) in protein side chains or peptides. Evidence from previous studies have indicated that polyphenols could reduce amyloid-formation via inhibiting fibril aggregation or steering oligomer formation into unstructured, nontoxic pathways. This effect was realized mainly through: (1) preventing conformational changes of precursor native proteins into amyloidogenic forms, (2) inhibiting the conversion of amyloidogenic precursors to amyloid fibrils, or (3) disrupting preformed fibrils meanwhile destructing the aggregation conditions. These findings imply that polyphenols could play a vital role in inhibiting protein misfolding, which might be useful for the prevention of various neurodegenerative diseases.

Design and preparation of hollow SiO2 nanospheres/SiC-based nanocomposite fiber membrane for high temperature thermal insulators

Silicon carbide (SiC) fibers are attractive for their thermal stability and chemical erosion resistance. However, the practical application of SiC fiber in the fields of thermal insulation is limited owing to its high intrinsic thermal conductivity. Herein, a novel closed cell structured SiC-based nanocomposite fiber (NCF) using hollow SiO 2 nanospheres (HSNSs) as pore forming agent were designed by precursor conversion method combined with electrospinning technology. According to the content and size of HSNSs, NCFs with different pore size and porosity could be obtained. When the content of HSNSs reached 15%, a large number of closed cells were constructed inside the fiber, which broke the continuity of solid heat transfer and endowed it with excellent thermal insulation performance (∼0.105 W m −1 K −1 at 1000 °C). Meanwhile, the NCFs showed excellent high-temperature resistance and mechanical properties, which makes it have a wide application prospect as a high temperature thermal insulator. This research also offers a new insight for the development of SiC-based fiber with multiple functions to meet various applications, such as catalyst supporters and microwave absorbers. • A new type of porous insulation material with closed cell structure is designed. • Multiple phases enhance interface thermal resistance and infrared shielding performance. • Hollow SiO 2 spheres significantly reduces the thermal conductivity of the fibers. • The nanocomposite fibers show great application prospects as high temperature thermal insulators.

Photoluminescence mechanism of carbon dots: triggering high-color-purity red fluorescence emission through edge amino protonation

Due to complex structure and surface functionalities, photoluminescence mechanisms of Carbon Dots are unknown, and it is challenging to synthesize Carbon Dots to achieve the desired optical properties. Herein, Carbon Dots simultaneously exhibiting high-color-purity (FWHM~24 nm) long wavelength one-photon fluorescence emission at 620 nm and NIR induced two-photon fluorescence emission at 630 and 680 nm are prepared by edge amino protonation treatment. Systematic analysis reveals that the protonation of 2,3-diaminophenazine changes the molecular state of Carbon Dots, decreases the photon transition band gap, and triggers red fluorescence emission with the dramatically narrowed peak width. As the oxidation products of reactant o-phenylendiamine, the emergence of 2,3-diaminophenazine as a photoluminescence determiner suggests that fluorophore products of precursor conversion are viable determinants of the desired luminescence properties of Carbon Dots. This work shows a new way for predicting and controlling photoluminescence properties of Carbon Dots, and may guide the development of tunable Carbon Dots for a broad range of applications.

Co-electrolysis toward value-added chemicals

Current major electrocatalytic reactions, such as hydrogen evolution reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction, focus on single-target chemical production, which suffers from strong competitive reactions at the same electrodes and/or high energy barrier reactions at the counterpart electrodes. The co-electrolysis of more than one kind, typically two kinds, of chemical precursors in one electrolytic system is therefore a highly attractive strategy for both energy input reduction and concurrent production of double value-added chemicals. Exciting progress has been achieved in this area recently, and a timely review on this specific topic will be highly desired. In this review, the reported co-electrolysis systems are classified into four categories: (1) agent sacrificing at one electrode promoting electrochemical precursor conversion at the other; (2) parallel electrochemical precursor conversions, i.e., electrosyntheses, simultaneously at both sides; (3) electrochemical conversions of two precursors at both sides into one/the same product; (4) double/multiple electrochemical conversions at one side. The current challenges and future opportunities of co-electrolysis toward high value-added products are discussed at the end.

Research on the composition of UV curing modified compounds for 3D printing based on HyperChem simulation

The precursor conversion method provides the possibility of 3D printing ceramic materials, and the resin system with polysilazane as the precursor is expected to prepare high-performance ceramic materials for aviation. In this paper, the UV curing reaction system of polysilazane for 3D printing is taken as the research object, and hyperchem8.0 software is used as the research means. The model construction, chemical bond energy calculation, reaction enthalpy calculation and other modules in the software are used to simulate and predict the reaction process and mechanism of UV curing, which provides a theoretical basis for the selection and optimization of the subsequent UV curing reaction system for 3D printing.

Tailoring Distinct Reactive Environments in Lewis Acid Zeolites for Liquid Phase Catalysis

ConspectusLewis acidic zeolites are microporous crystalline materials that offer promise as catalysts for the activation and conversion of biomass-derived precursors in the liquid phase due to their unique water tolerance and synthetic versatility. The active site environment in zeolite catalysts is multifaceted in nature and is composed of a primary catalytic binding site, the secondary pore structure that confines such binding sites, and occluded solvent and reactant molecules that interact with adsorbed species. Moreover, Lewis acidic heteroatoms can adopt structurally diverse coordination that selectively catalyze different classes of chemical transformations and can be difficult to control synthetically or characterize spectroscopically. Thus, precise mechanistic interpretation of liquid-phase zeolite catalysis necessitates the development of synthetic, spectroscopic, and kinetic methods that can decouple such complex active site structures and probe the interactions that occur between confined active sites, solvent and reactant molecules, and adsorbed intermediates and transition states.In this Account, we describe the development and application of synthetic, spectroscopic, and kinetic methods to investigate chemically distinct Lewis acid zeolite environments in siliceous zeolites for liquid-phase catalysis. Identification of unique Lewis acidic active site structures relied on the development of direct and indirect solid-state nuclear magnetic resonance (NMR) methods that probe the number and connectivity of framework Lewis acid sites for a diverse range of metal heteroatoms. Such methods enabled the quantitative comparison of catalytic turnover rates, on a per active site basis, measured on different catalysts in order to establish structure–function relationships between active site structure and reactivity. Rigorous normalization of turnover rate further permits comparison of catalytic turnover rates across materials of varying topology, metal heteroatom identity, solvent, and framework polarity to extract salient thermodynamic descriptors of catalysis through kinetic probes. Ex situ interrogation of alcohols adsorbed within hydrophobic and hydrophilic Sn-containing zeolites revealed that hydrophobic voids induce structural order on confined alcohol hydrogen-bonding networks, which give rise to enhanced turnover rates of liquid-phase transfer hydrogenation catalysis. This acceleration of turnover rates arises because ordered alcohol networks occluded within the pores of hydrophobic zeolites stabilize adsorbed transfer hydrogenation intermediates and transition states to a greater extent than liquidlike solvent networks observed in hydrophilic zeolites. The effects of confined solvent molecules can also influence catalysis, independent of framework polarity, due to differences in solvent polarity and substituent effects, which alter turnover rates via changes in how different solvent molecules interact with adsorbed intermediates and transition states. These observations underscore new opportunities to leverage specific interactions between active sites and solvent molecules to influence solvent organization and transition state stability at confined solid–liquid interfaces.This work illustrates the importance of quantitative methods that count distinct active site structures in order to compare catalytic materials on a per active site basis. This information can be used to develop new synthetic procedures that predictably manipulate the functionalization of both the primary binding site and the secondary reaction environment to tailor catalytic function for a desired chemistry. Collectively, these advances highlight strategies to engineer and characterize microporous catalysts with unique reaction environments in order to capture salient mechanistic features and navigate the complex free energy landscape of catalysis in condensed solvent systems.

B4C/SiC ceramic hollow microspheres prepared by slurry-coating and precursor conversion method

In this work, a new approach to fabricate B4C/SiC ceramic hollow microsphere was established through combination of slurry-coating and precursor conversion method. Firstly, different slurries were prepared using modified B4C powder with addition of PCS and LPCS. Subsequently, slurry was coated on a POM microsphere, followed by crosslinking, POM decomposition and heat-treatment at 1100 °C. Finally, the B4C/SiC hollow microspheres with average diameter of 1.6–1.9 mm and thickness of 10–60 μm were obtained. The roughness (Ra) of outer surface was as low as 40.3 nm with high sphericity of 99.6%. Deoxidation was also explored by heat treatment at 1700 °C. The oxygen content was decreased from 11.06 wt.% to 0.37 wt.%, and crush load was promoted from 1.73 N to 4.50 N. The preparative method of B4C/SiC ceramic hollow microspheres in this work can be easily extended for large-scale production.