Catalyst Molecules Research Articles

Effects of base catalyst on the physicochemical properties and surface reactivity of silica nanoparticles

The surface reactivity of silica particles is a key property that enhances their versatility in various industries. Therefore, it is imperative to investigate the effects of different base catalysts on the surface reactivity of silica nanoparticles. Silica nanoparticles were synthesised using potassium hydroxide (KOH) and sodium hydroxide (NaOH) as strong base catalysts, as well as ammonia (NH3) and lysine amino acid as weak base catalysts. The particle size was observed to increase with the pH of the reaction mixture. Additionally, X-ray photoelectron spectroscopy (XPS) revealed that the catalyst molecules adsorb onto the particle surface, thereby enhancing their surface reactivity. Sodium and potassium ions were found to significantly improve surface reactivity during silanisation, with KOH- and NaOH-sil-C8 samples exhibiting high silane grafting density (> 2.58 alkyl chains/nm2). These findings indicate that the type of base catalyst plays a crucial role in tailoring the properties and surface reactivity of silica nanoparticles.

Pentagon-Rich Caged Carbon Catalyst for the Oxygen Reduction Reaction in Acidic Electrolytes.

The interaction between electron spin and oxygen molecules in non-platinum catalysts, particularly carbon catalysts, significantly influences the catalytic performance of the oxygen reduction reaction (ORR). A promising approach to developing high-performance catalysts involves introducing five-membered ring structures with spin into graphitic carbons. In this study, we present the successful synthesis of cage-like cubic carbon catalysts enriched with pentagon structures using pentagon ring-containing C60 and a NaCl template. The number of pentagons contained in the structure was increased by doping with nitrogen and annealing, and the number of electron spins also increased, thereby improving catalytic activity. The prepared catalyst exhibits remarkable activity in ORR under acidic electrolytes. Furthermore, we elucidate the correlation between the pentagon structure, the number of spin, and catalytic activity, demonstrating that enhanced activity is contingent upon the presence of spin. Density functional theory (DFT) calculations support the role of spin in improving activity. The concept of spin and the introduction of pentagon structures provide new design principles for carbon catalysts.

Effect of Catalyst Concentration on Reaction Rate in Organic Synthesis in Kenya

Purpose: The aim of the study was to assess the effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low-cost advantage as compared to field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: Increased catalyst concentration typically enhances the reaction rate by providing more active sites for the reactants to interact, thereby accelerating the reaction process. This phenomenon follows the principles of collision theory, which states that a higher concentration of catalyst molecules leads to more frequent collisions with reactant molecules, thus increasing the likelihood of successful reactions. Studies have shown that in many organic syntheses, an optimal catalyst concentration exists where the reaction rate is maximized; beyond this point, further increases in catalyst concentration may result in negligible improvements or even adverse effects due to catalyst aggregation or inhibition. Additionally, the nature of the catalyst, its dispersion in the reaction medium, and the specific reaction mechanism all play significant roles in determining the overall impact of catalyst concentration on reaction kinetics. Consequently, fine-tuning the catalyst concentration is essential for optimizing reaction conditions, improving yields, and achieving desired product selectivity in organic synthesis. Implications to Theory, Practice and Policy: Transition state theory, collision theory and michaelis menten kinetics may be used to anchor future studies on assessing effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Practical guidelines are crucial for optimizing catalyst concentration in specific reaction types and industrial settings. Establishing regulatory frameworks that incentivize efficient catalyst concentration practices within industries is imperative.

On-Demand Activatable and Integrated Bioorthogonal Nanocatalyst against Biofilm-Associated Infections.

Bioorthogonal chemistry has emerged as a powerful tool for manipulating biological processes. However, difficulties in controlling the exact location and on-demand catalytic synthesis limit its application in biological systems. Herein, this work constructs an activatable bioorthogonal system integrating a shielded catalyst and prodrug molecules to combat biofilm-associated infections. The catalytic species is activated in response to the hyaluronidase (HAase) secreted by the bacteria and the acidic pH of the biofilm, which is accompanied by the release of prodrugs, to achieve the bioorthogonal catalytic synthesis of antibacterial molecules in situ. Moreover, the system can produce reactive oxygen species (ROS) to disperse bacterial biofilms, enabling the antibacterial molecules to penetrate the biofilm and eliminate the bacteria within it. This study promotes the design of efficient and safe bioorthogonal catalysts and the development of bioorthogonal chemistry-mediated antibacterial strategies.

Tailored Metal-Organic Frameworks for Water Purification: Perfluorinated Fe-MOFs for Enhanced Heterogeneous Catalytic Ozonation.

An industrially viable catalyst for heterogeneous catalytic ozonation (HCO) in water purification requires the characteristics of good dispersion of active species on its surface, efficient electron transfer for ozone decay, and maximum active species utilization. While metal-organic frameworks (MOFs) represent an attractive platform for HCO, the metal nodes in the unmodified MOFs exhibit low catalytic activity. Herein, we present a perfluorinated Fe-MOF catalyst by substituting H atoms on the metalated ligands with F atoms (termed 4F-MIL-88B) to induce structure evolution. The Lewis acidity of 4F-MIL-88B was enhanced via the formation of Fe nodes, tailoring the electron distribution on the catalyst surface. As a result of catalyst modification, the rate constant for degradation of the target compounds examined increased by ∼700% compared with that observed for the unmodified catalyst. Experimental evidence and theoretical calculations showed that the modulated polarity and the enhanced electron transfer between the catalyst and ozone molecules contributed to the adsorption and transformation of O3 to •OH on the catalyst surface. Overall, the results of this study highlight the significance of tailoring the metalated ligands to develop highly efficient and stable MOF catalysts for HCO and provide an in-depth mechanistic understanding of their structure-function evolution, which is expected to facilitate the applications of nanomaterial-based processes in water purification.

Complexation between butyl xanthate and Cu enhanced peroxydisulfate activation and cation redox cycle by Fe-Cu-LDH/biochar

Butyl xanthate (BX) is one of the most widely used collector in sulfide flotation. It is harmful to human health but its degradability has not been addressed in depth. In this study, Fe-Cu-Layered double hydroxides/Biochar composites (Fe-Cu-LDH/BC) were prepared and firstly used to activate peroxydisulfate (PDS) for degradation of butyl xanthate. More than 90 % of BX could be completely degraded within 10 min under conditions of 20 mg/L BX, 0.2 g/L LDH/BC and 0.1 mM PDS. The high degradation efficiency was owing to the complex formation between catalyst and contaminant molecule by a coordination bond of the Cu in Fe-Cu-LDH/BC and the S in BX. Through DFT calculations, it could be found that this complexation enhanced the adsorption efficiency of LDH/BC on PDS and the reactivity of the Cu site. EPR was applied to analyze the reactive substances in the reaction, and various reactive oxygen species such as O2•−, •OH and SO4•− were detected in the process. In addition, LC-MS was used to analyze and speculate the intermediates and degradation pathways of BX. In conclusion, this material can promote the degradation of BX in water under different conditions and has great potential in treating mine wastewater. Meanwhile, this study proposes new ideas for the synthesis of new catalysts for the efficient degradation of pollutants.

Ultrafast Electron Transfer from CuInS2 Quantum Dots to a Molecular Catalyst for Hydrogen Production: Challenging Diffusion Limitations.

Systems integrating quantum dots with molecular catalysts are attracting ever more attention, primarily owing to their tunability and notable photocatalytic activity in the context of the hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR). CuInS2 (CIS) quantum dots (QDs) are effective photoreductants, having relatively high-energy conduction bands, but their electronic structure and defect states often lead to poor performance, prompting many researchers to employ them with a core-shell structure. Molecular cobalt HER catalysts, on the other hand, often suffer from poor stability. Here, we have combined CIS QDs, surface-passivated with l-cysteine and iodide from a water-based synthesis, with two tetraazamacrocyclic cobalt complexes to realize systems which demonstrate high turnover numbers for the HER (up to >8000 per catalyst), using ascorbate as the sacrificial electron donor at pH = 4.5. Photoluminescence intensity and lifetime quenching data indicated a large degree of binding of the catalysts to the QDs, even with only ca. 1 μM each of QDs and catalysts, linked to an entirely static quenching mechanism. The data was fitted with a Poissonian distribution of catalyst molecules over the QDs, from which the concentration of QDs could be evaluated. No important difference in either quenching or photocatalysis was observed between catalysts with and without the carboxylate as a potential anchoring group. Femtosecond transient absorption spectroscopy confirmed ultrafast interfacial electron transfer from the QDs and the formation of the singly reduced catalyst (CoII state) for both complexes, with an average electron transfer rate constant of <kET> ≈ (10 ps)-1. These favorable results confirm that the core tetraazamacrocyclic cobalt complex is remarkably stable under photocatalytic conditions and that CIS QDs without inorganic shell structures for passivation can act as effective photosensitizers, while their smaller size makes them suitable for application in the sensitization of, inter alia, mesoporous electrodes.

Study on Adsorption of Diesel Molecules on MoS&lt;sub&gt;2&lt;/sub&gt; and NiMoS Catalysts

For deep insight into complex reaction system of diesel hydrotreating, the monolayer adsorption and competitive adsorption of typical reactant molecules (phenanthrene, naphthalene, acridine, quinoline, dibenzothiophene, 4,6-dimethyldibenzothiophene and H2) on MoS2 and NiMoS catalyst models with different structures were investigated. The basal plane is discovered to be the best physical adsorption position for all molecules in MoS2 series catalysts. Following saturation of the basal plane, reactant molecules will be adsorbed at Mo edge first, and Mo edge is more prone to bimolecular or multimolecular adsorption than S-edge, implying that Mo edge active sites play an important role in diesel hydrotreating. Naphthalene has a higher adsorption capacity in the partial pressure system that simulates the actual reaction atmosphere, and it is the most likely reactant molecule to predominately occupy active sites, but 4,6-dimethyl dibenzothiophene still exhibits good competition adsorption performance due to its high adsorption capacity and heat release. Interestingly, after phenanthrene adsorption, the secondary adsorption of hydrogen decreases in all of the catalyst models studied, indicating that phenanthrene is one of the most important molecules influencing hydrogen adsorption. Furthermore, the secondary adsorption of hydrogen after phenanthrene adsorption decreased the most on Tri-S50 catalyst. It shed light on that the activity and stability of Tri-S50 catalyst was most likely to decrease during diesel hydrotreating because of the notable inhibition on adsorption of hydrogen molecules brought by phenanthrene adsorption. It presents a theoretical basis for the design and development of highly efficient diesel hydrotreating catalysts.

Stabilizing molecular catalysts on metal oxide surfaces using molecular layer deposition for efficient water oxidation.

The stabilization of metal-oxide-bound molecular catalysts is essential for enhancing their lifetime and commercial viability in heterogeneous catalysis. This is particularly relevant in dye-sensitized photoelectrochemical cells (DSPECs), where the surface-bound chromophores and catalysts exhibit instability in aqueous environments, particularly at elevated pH levels. In this work, we have successfully employed molecular layer deposition (MLD) to stabilize ruthenium-based catalysts (RuCP(OH2)2+, denoted as RuCat). The application of polyimide (PI) via MLD onto the porous nanoITO surface significantly improved the stabilization of RuCat molecules for water oxidation. Additionally, time-resolved photoluminescence (TRPL) spectroscopy and femtosecond transient absorption spectroscopy (fs-TAS) results indicated that the MLD-deposited PI effectively preserved the robust redox capacity of the photogenerated electron-hole pairs associated with the catalyst molecules, thereby facilitating more efficient charge transfer. This research presents a novel approach for stabilizing surface-bound small molecules, which may contribute to advancements in heterogeneous catalysis and enhance its commercial viability.

КИНЕТИЧЕСКИЙ АНАЛИЗ ТЕХНОЛОГИЧЕСКИХ КРИТЕРИЕВ ЭФФЕКТИВНОСТИ ПРОЦЕССА ОКИСЛЕНИЯ ЭТИЛБЕНЗОЛА В ПРИСУТСТВИИ КОМПЛЕКСОВ ДИБЕНЗО-18-КРАУН-6 ЭФИРА С ХЛОРИДАМИ CA, SR, BA

A kinetic scheme is proposed that is common to the processes of ethylbenzene oxidation and ethylbenzene hydroperoxide decomposition in the presence of dibenzo-18-crown-6 ether complexes with Ca, Sr, and Ba chlorides. The scheme includes reactions of the formation of intermediate adducts from components of the reaction mixture and catalyst molecules, classical reactions of initiation, propagation and termination of the chain, reactions of initiation and propagation of the chain with the participation of intermediate adducts, and molecular reactions (includingthose with the participation of intermediate adducts).Basedonexperimentaldataandtheproposedscheme, akineticmodelwasmade.The kinetic model, written in the form of nonlinear differential equations according to the mass action law describes in time the rate of change of the concentrations of all components of reaction mixtures for ethylbenzene oxidation and ethylbenzene hydroperoxide decomposition in the presence of dibenzo-18-crown-6 ether complexes with Ca, Sr, Ba chlorides. As a result of solving the inverse kinetic problem using the zero-order direct search method, the values of reaction rate coefficients were found where the kinetic model reproduces the experimental values of the concentrations of all components of the reaction mixtures of the processes under consideration within the average relative error of 25%.As a result of the analysis based on the kinetic model, it was established that the conversion of ethylbenzene in the process of its oxidation is most affected by the reaction of ethylbenzene with the ethylbenzene peroxyl radical (target reaction).Using the kinetic model, the following was shown: 1) the values of the conversion of ethylbenzene, depending on the nature of the catalyst, line up in a row that corresponds to a number of values of the reaction rates of ethylbenzene with ethylbenzene peroxyl radical; 2) the model qualitatively reproduces the trend of selectivity changes when changing the catalyst.

The role of surface functionalization in quantum dot-based photocatalytic CO2 reduction: balancing efficiency and stability.

Photocatalytic CO2 reduction offers a promising strategy to produce hydrocarbons without reliance on fossil fuels. Visible light-absorbing colloidal nanomaterials composed of earth-abundant metals suspended in aqueous media are particularly attractive owing to their low-cost, ease of separation, and highly modifiable surfaces. The current study explores such a system by employing water-soluble ZnSe quantum dots and a Co-based molecular catalyst. Water solubilization of the quantum dots is achieved with either carboxylate (3-mercaptopropionic acid) or ammonium (2-aminoethanethiol) functionalized ligands to produce nanoparticles with either negatively or positively-charged surfaces. Photocatalysis experiments are performed to compare the effectiveness of these two surface functionalization strategies on CO2 reduction and ultrafast spectroscopy is used to reveal the underlying photoexcited charge dynamics. We find that the positively-charged quantum dots can support sub-picosecond electron transfer to the carboxylate-based molecular catalyst and also produce >30% selectivity for CO and >170 mmolCO gZnSe-1. However, aggregation reduces activity in approximately one day. In contrast, the negatively-charged quantum dots exhibit >10 ps electron transfer and substantially lower CO selectivity, but they are colloidally stable for days. These results highlight the importance of the quantum dot-catalyst interaction for CO2 reduction. Furthermore, multi-dentate catalyst molecules create a trade-off between photocatalytic efficiency from strong interactions and deleterious aggregation of quantum dot-catalyst assemblies.

External [1 1 1] facets on nanorod gamma alumina boosts catalytic reductive amination of carbonyl compound to primary amine

Hydrogen spillover had played a significant role in catalytic processes involving reducible oxide supported metal catalyst and hydrogen molecule. Herein, crystal plane regulative hydrogen spillover strategy for the effective reductive amination on Ni/Al2O3 was developed. A rod-like alumina supported Ni catalyst with primarily external (111) facets was prepared. In the presence of NH3 and H2, Ni/Al2O3 (111) exhibited a turnover number of 30.4 h−1, which was 136-fold higher than that of Ni/Al2O3 (110) in the reductive amination of furfural to furfuryl amine. For the Ni/Al2O3 (111) catalyst, Al2O3 (111) facets exhibited strong Lewis acidity, resulting in an enhanced H affinity of Al2O3 (111) and a positively charged of Ni through electronic interaction. It was revealed that strong H affinity of Al2O3 (111) and positively charged Ni sites significantly promoted hydrogen migration from Ni surface to Al2O3 (111) facets, which effectively prevented the Ni sites from hydrogen poisoning and enhanced the adsorption and activation of NH3 and intermediates for reductive amination. Consequently, the activation energy of Schiff base reductive ammonolysis was obviously reduced, resulting in high inherent activity for furfural reductive amination to furfuryl amine. This work developed a new strategy for high efficiency reductive amination catalyst in terms of hydrogen spillover effect.

A Multi-Pyridine-Anchored and -Linked Bilayer Photocathode for Water Reduction.

The development of efficient photocathodes is of critical importance for the constructions of promising tandem photo-electrochemical cells. Most known dye-sensitized photocathodes are prepared with the conventional carboxylic or phosphonic acid anchors and require the presence of other terminal linking groups to connect catalysts; they suffer from high synthetic difficulty and low adsorption stability in aqueous media. Here, a compact bilayer photocathode has been prepared by using a pyrene-based photosensitizer with multiple terminal pyridine moieties as both the anchoring and linking groups to connect a Co hydrogen-evolution catalyst to the NiO substrate. The catalyst and dye molecule are assembled in a layer-by-layer manner on NiO through the metal-pyridine coordination. This photocathode exhibits good dye adsorption stability in aqueous media. A stable cathodic photocurrent of 70 μA cm-2 was achieved, with H2 being generated at the photocathode under the visible-light irradiation. The Faraday efficiency of H2 evolution was estimated to be 9.1 %. Transient absorption spectral studies suggest that the interfacial hole transfer occurs within a few picoseconds. The integration of the organic photosensitizer with pyridine anchoring and linking groups is expected to provide a simple method for the fabrication of stable and efficient photocathodes.

A One‐Pot Three‐In‐One Synthetic Strategy to Immobilize Cobalt Corroles on Carbon Nanotubes for Oxygen Electrocatalysis

AbstractMolecular electrocatalysis requires the immobilization of molecular catalysts on electrode materials for practical uses. Direct adsorption of catalyst molecules on electrode materials is simple, but grafting molecules through chemical bonds can significantly improve electrocatalytic efficiency and durability. However, designing and synthesizing catalyst molecules to simultaneously improve catalytic activities and realize easy grafting on electrodes is challenging. The study herein reports on a one‐pot strategy to graft Co corroles on pyridine‐modified carbon nanotubes (CNTs) for oxygen electrocatalysis. By modifying CNTs with pyridines, the resulting pyridine‐modified CNTs can function as platforms to grab in situ generated Co corroles through the axial pyridine ligation on Co. Such an immobilization strategy combines three effects for the regulation of electrocatalysis, including the axial ligand effect, the electron transfer effect, and the chemical bond effect. The resulting hybrid materials show high efficiency for oxygen electrocatalysis, and the Zn–air battery assembled using these materials displays comparable performance as the Pt/Ir‐based battery. Moreover, the electrocatalytic efficiency of these hybrid materials can be systematically tuned by using different pyridines, highlighting the controllable feature of this strategy. Therefore, this work is significant to present a one‐pot three‐in‐one strategy to immobilize catalyst molecules on CNTs for electrocatalysis.

Enhancing Metallocene Catalyst Activity: Utilizing Layered Double Hydroxide for Ethylene–Propylene Copolymerization

AbstractThis study reports the heterogenization of metallocene catalysts on sodium dodecyl sulfate (DDS)‐modified layered double hydroxides (LDHs) for efficient ethylene–propylene (EP) slurry‐phase copolymerization. The LDH support offers considerable compositional tunability. NiFe LDHs with different anions () and metallic compositions are applied as support for the metallocene catalysts; these significantly influence the catalytic properties of the heterogenized catalyst system. The supported‐catalyst intercalating DDS− anion in the galleries of NiFe and ZnAl LDHs demonstrates a high catalytic activity. They produce EP copolymers with high molecular weights (Mw) and wide polydispersity, compared with the homogeneous Zr catalyst. Further, the supported catalyst complex containing anion produces EP with a tenfold high Mw and demonstrate subdued catalytic activity. The higher basicity of the support is associated with the enhanced activity and the wider polydispersity of the EP pertaining to the different interactions of the catalyst molecule with the support. Overall, Ni‐containing LDH favors a higher activity, whereas Fe‐containing LDH favors a higher Mw. Therefore, NiFe‐based LDH results in both higher activity and molecular weight. 13C and 27Al magnetic angle spinning solid‐state nuclear magnetic resonance confirm the formation of the supported catalyst complex.

Mechanistic Elucidation of a Radical‐Promoted Hydrogenation Relevant to Borrowing Hydrogen Catalysis

AbstractIn the borrowing hydrogen catalysis, hydrogenation of an in situ generated imine or olefinic bond is a crucial step. There is a growing body of literature in olefinic hydrogenation promoted by metal hydride of Earth‐abundant metals, where radical mechanism is followed. This report presents a thorough study of the mechanistic details of a nickel catalyzed α‐alkylation of ketones with secondary alcohols and showcases that the olefinic hydrogenation of an enone happens, completely bypassing the involvement of a metal hydride. This pathway is radical promoted, where a single electron reduction of the substrate olefin and a subsequent hydrogen atom transfer step are most critical. A series of control reactions, detection of critical reaction intermediates, and radical probe experiments provide compelling proofs for such radical‐promoted olefinic hydrogenation. The experimental clues, further aided by DFT calculations altogether suggest the precise one‐electron chemistry where the involvement of metal‐hydride is not required. Notably, the redox non‐innocence of the azophenolate backbone, as well as imposed noninnocence of the substrate olefin, when bound to the catalyst molecule makes such mechanism feasible.

Boosting Fenton's Oxidation Reaction by a Food Waste-Derived Catalyst for Oxidizing Organic Dyes: Synergistic Effect of Complex Iron Oxides and the Layer Carbon Structure.

The constant increase in the human population drives the demand for food supply and thereby increasing the food wastage dramatically all over the world. Especially, around 60% of banana biomass has been generated as inedible domestic waste. Herein, we successfully employed banana waste as a catalyst for Fenton's oxidation reaction. The biomass-derived catalysts were subjected to various characterization techniques such as XRD, ATR-FTIR, confocal Raman spectroscopy, and XPS, XRF, BET, SEM, and TEM analyses. The XRD results revealed that, after carbonization of the dried banana bract material, a perloffite-like metal oxide phase was formed due to the aerial oxidation reaction. Characterization results of Raman and ATR-FTIR confirm that the carbonized catalyst possesses a layer-like structure with different types of functional groups. The calcium, magnesium, potassium, sodium, and iron are the dominating metal species in the resultant material, which was evident from the XRF and EDAX analyses. The carbonized banana bract catalyst is successfully utilized for the Fenton's oxidation reaction at neutral pH. The experimental results showed that the degradation efficiency of the fresh catalyst was 95% in 4 h of reaction time, and the stability of the catalyst was retained up to nine consecutive cycles. The high activity of MB, methylene blue, is mainly attributed to the strong interaction between oxy functional groups of the catalyst and MB molecule as compared to RhB. Further, the calculated efficiency of the hydrogen peroxide was found to be 99% and the self-decomposition of hydrogen peroxide by the formed metal oxides was highly limited.

Integration of Single-Atom Catalyst with Z-Scheme Heterojunction for Cascade Charge Transfer Enabling Highly Efficient Piezo-Photocatalysis.

Piezo-assisted photocatalysis (namely, piezo-photocatalysis), which utilizes mechanical energy to modulate spatial and energy distribution of photogenerated charge carriers, presents a promising strategy for molecule activation and reactive oxygen species (ROS) generation toward applications such as environmental remediation. However, similarly to photocatalysis, piezo-photocatalysis also suffers from inferior charge separation and utilization efficiency. Herein, a Z-scheme heterojunction composed of single Ag atoms-anchored polymeric carbon nitride (Ag-PCN) and SnO2- x is developed for efficient charge carrier transfer/separation both within the catalyst and between the catalyst and surface oxygen molecules (O2 ). As revealed by charge dynamics analysis and theoretical simulations, the synergy between the single Ag atoms and the Z-scheme heterojunction initiates a cascade electron transfer from SnO2- x to Ag-PCN and then to O2 adsorbed on Ag. With ultrasound irradiation, the polarization field generated within the piezoelectric hybrid further accelerates charge transfer and regulates the O2 activation pathway. As a result, the Ag-PCN/SnO2- x catalyst efficiently activates O2 into ·O2 - , ·OH, and H2 O2 under co-excitation of visible light and ultrasound, which are consequently utilized to trigger aerobic degradation of refractory antibiotic pollutants. This work provides a promising strategy to maneuver charge transfer dynamics for efficient piezo-photocatalysis by integrating single-atom catalysts (SACs) with Z-scheme heterojunction.

Ir0/graphdiyne atomic interface for selective epoxidation.

The development of catalysts that can selectively and efficiently promote the alkene epoxidation at ambient temperatures and pressures is an important promising path to renewable synthesis of various chemical products. Here we report a new type of zerovalent atom catalysts comprised of zerovalent Ir atoms highly dispersed and anchored on graphdiyne (Ir0/GDY) wherein the Ir0 is stabilized by the incomplete charge transfer effect and the confined effect of GDY natural cavity. The Ir0/GDY can selectively and efficiently produce styrene oxides (SO) by electro-oxidizing styrene (ST) in aqueous solutions at ambient temperatures and pressures with high conversion efficiency of ∼100%, high SO selectivity of 85.5%, and high Faradaic efficiency (FE) of 55%. Experimental and density functional theory (DFT) calculation results show that the intrinsic activity and stability due to the incomplete charge transfer between Ir0 and GDY effectively promoted the electron exchange between the catalyst and reactant molecule, and realized the selective epoxidation of ST to SO. Studies of the reaction mechanism demonstrate that Ir0/GDY proceeds a distinctive pathway for highly selective and active alkene-to-epoxide conversion from the traditional processes. This work presents a new example of constructing zerovalent metal atoms within the GDY matrix toward selective electrocatalytic epoxidation.

Dual-Site Polymeric Heterogeneous α-Diimine Ni Catalysts with Tailored Spatial Distribution for Ethylene Polymerization

Dual-site molecular heterogeneous catalysts for synthesizing polyolefin in-reactor blends have received increasing attention in academia and industry. It is hypothesized that the mesoscopic spatial distribution of different catalyst molecules in dual-site catalyst particles will have significant impacts on the superstructures and properties of polyolefin in-reactor blending products. It is difficult for typical heterogenization to tune the spatial distribution of different molecular catalyst components in the particles. In this contribution, a self-supporting strategy based on nickel-catalyzed precipitation coordination polymerization of a polar monomer was used to achieve not only heterogenization of the catalysts but also spatial distribution tuning of different catalytic components in the polymeric particles. These polymeric heterogeneous dual-site catalysts led to higher activities compared with homogeneous molecular catalysts. Moreover, they resulted in high molecular weights, good morphological control, and improved compatibility with polar materials. The composition and physical properties of the blend can be controlled by the molar ratio of the two catalytic components. Interestingly, it was shown that the different spatial distribution types can result in great differences in thermal, mechanical, and rheological properties and applications of the obtained blends.