Catalyst-Free Selective Oxidation of Diverse Olefins to Carbonyls in High Yield Enabled by Light under Mild Conditions

The selective oxidation of olefins, in particular, aromatic olefins to carbonyls, is of significance in organic synthesis. In general, stoichiometric toxic oxidants or a high-cost catalyst is required. Herein we report a novel and practical light-enabled protocol for the synthesis of carbonlys in high yield through a catalyst-free oxidation of olefins using H2O2 as a clean oxidant. A broad scope of carbonyls can be synthesized in high yield, and no catalyst or toxic oxidant is required

Ni Nanoparticles Grown on SiO₂ Supports Using a Carbon Interlayer Sacrificial Strategy for Chemoselective Hydrogenation of Nitrobenzene and <i>m</i>‑Cresol

To efficiently increase the dispersity of metal nanoparticles (NPs) of the supported-type catalyst is crucial for promoting their catalytic performance owing to the enlarged amount of exposed active sites and the strengthened metal–support interaction. Therefore, to develop a facile and practical method for preparing a supported-type catalyst with high dispersity is of great significance, but remains a challenge. In this work, inspired by the previously reported non-noble metal sacrificial approach, we report a facile and practical carbon interlayer sacrificial (CIS) strategy for preparing supported Ni NP catalysts on silica rod (10%Ni/r-SiO2-CIS) with high dispersity. This strategy involves two steps: one is depositing carbon on silica rod (r-SiO2) to form the corresponding carbon-coated silica (r-SiO2@C) carrier through a hydrothermal process in the presence of glucose; the other is loading metal precursor on r-SiO2@C through an incipient wetness impregnation (IWI) process followed by hydrogenation for carbon elimination. The method has been extended to the preparation of supported Ni NPs on the silica sphere (10%Ni/s-SiO2-CIS) with high Ni dispersity by using the silica sphere (s-SiO2) as the carrier. For comparison, the conventional-supported Ni NP catalysts (10%Ni/r-SiO2 and 10%Ni/s-SiO2) were also prepared by using a similar method to that for 10%Ni/r-SiO2-CIS and 10%Ni/s-SiO2-CIS except for absence of the carbon-coating process. Owing to the more exposed active sites and the strengthened metal–support resulting from the higher Ni dispersity, both 10%Ni/r-SiO2-CIS and 10%Ni/s-SiO2-CIS catalysts show much superior catalytic properties for the chemoselective hydrogenation of nitrobenzene and m-cresol to their corresponding 10%Ni/r-SiO2 and 10%Ni/s-SiO2. This work opens up an avenue for designing and preparing other outstanding supported metal NP catalysts with high metal dispersity for diverse catalytic transformations

Computational Design of a CoCu-Modified Indium Oxide Catalyst Promoting CO₂ Activation and Hydrogenation through Electronic Regulation

Density functional theory calculations identified a CoCu3-cluster-modified In2O3 catalyst promoting CO2 activation and hydrogenation through electronic regulation. The introduction of CoCu3 into In2O3 facilitated the formation of oxygen vacancy and provided new active sites for CO2 activation and hydrogenation, resulting in a small barrier (0.28 eV) for the key HCOO* intermediate formation over the Co–Cu site on the D4 surface of CoCu3/In2O3(110)

NiPN/Ni Nanoparticle-Decorated Carbon Nanotube Forest as an Efficient Bifunctional Electrocatalyst for Overall Water Splitting in an Alkaline Electrolyte

In this work, a multi-interfacial nickel phosphide-nitride/nickel (NiPN/Ni) nanoparticle (NP)-decorated P,N-doped carbon nanotube (CNT) forest on carbon cloth (NiPN/Ni/CC-CNT2) with a high electrochemical active surface area was synthesized by a facile two-step approach involving the CNT forest growth with a subsequent controlled phosphorization/nitridation procedure, in which the initially loaded Ni species (active sites for growing CNT forest) serve as a precursor for synthesizing NiPN/Ni NP active species on CNT forest for water electrolysis. This is the first example that the loaded Ni sites for CNT forest growth were directly converted to active species for water electrolysis rather than be removed by acid treatment, which fully utilizes Ni resources and simultaneously avoids the waste acid environmental pollution. Thanks to the promoted mass/electron transfer by the CNT forest structure and the improved intrinsic activity by the multi-interfacial synergistic effect of nickel phosphide-nitride and nickel, the resultant NiPN/Ni/CC-CNT2 shows high activity toward hydrogen evolution reaction (HER, η10 = 56 mV and η100 = 186 mV) and oxygen evolution reaction (OER, η10 = 204 mV and η100 = 266 mV) in an alkaline medium. In addition, the assembled two-electrode electrolyzer with NiPN/Ni/CC-CNT2 as both the anode and cathode delivers low cell voltages of 1.49 and 1.74 V for 10 and 100 mA cm–2, respectively, associated with an excellent electrocatalytic durability for overall water splitting. The developed low-cost bifunctional NiPN/Ni/CC-CNT2 outperforms most of the reported electrocatalysts in literature and performs even better than the Pt and RuO2 benchmark electrocatalysts for HER and OER, respectively, at a large current density. Therefore, the fabricated NiPN/Ni/CC-CNT2 has shown great potential for large-scale commercial production of green hydrogen as a clean and renewable fuel to support the carbon neutralization strategy

Glucose-Assisted Preparation of a Nickel–Molybdenum Carbide Bimetallic Catalyst for Chemoselective Hydrogenation of Nitroaromatics and Hydrodeoxygenation of <i>m</i>‑Cresol

Developing a safe, facile, clean, low-cost, and scalable new method to replace the conventional methane reductive carburization process for preparing carbon-nanotube, coverage-free, highly dispersed, metal carbide based bimetallic catalysts without a sacrificial metal loading is of great significance but remains a challenge. In this work, we develop a facile and robust strategy for successfully preparing a highly dispersed supported nickel–molybdenum carbide (NiMo₂C) bimetallic catalyst on mesoporous silica [NiMo₂C/SBA-15­(Glu.)], in which the renewable glucose is employed to serve as an assisting agent for high metal dispersion within the mesoporous channels of SBA-15 in the impregnation process and as a carbon source to replace flammable methane for metal carbide formation through a reductive carburization process. From diverse characterization results, the as-prepared NiMo₂C/SBA-15­(Glu.) catalyst demonstrates a much higher metal dispersion (ca. 4.1 nm in this work vs ca. 80 nm aggregates by the conventional method, as proven by transmission electron microscopy, X-ray diffraction, CO chemosorption, etc.) and promoted synergy effect between Ni and Mo₂C than the NiMo₂C/SBA-15­(Ref.) prepared by a conventional impregnation method, followed by methane reductive carburization (as proven by X-ray photoelectron spectroscopy and H₂ temperature-programmed reduction); besides, the growth of carbon nanotubes is eliminated. As a consequence, the NiMo₂C/SBA-15­(Glu.) catalyst shows unexpectedly 18 times higher catalytic specific activity for chemoselective hydrogenation of nitrobenzene and 12 times higher for the hydrodeoxygenation of <i>m</i>-cresol than conventional NiMo₂C/SBA-15­(Ref.). Moreover, NiMo₂C/SBA-15­(Glu.) shows a notably different product distribution for the hydrodeoxygenation of <i>m</i>-cresol owing to the bifunctional effect of Mo₂C. The as-prepared supported NiMo₂C catalyst can be extended to other transformations, and also the developed method in this work can be extended for the preparation of other metal carbide catalysts toward diverse applications

Reconstructing Supramolecular Aggregates to Nitrogen-Deficient g‑C₃N₄ Bunchy Tubes with Enhanced Photocatalysis for H₂ Production

Developing a facile method to overcome the intrinsic shortcomings of g-C₃N₄ photocatalyst concerning its insufficient visible light absorption and dissatisfactory separation efficiency of charge carriers is of great significance but remains a challenge. In this work, we report, for the first time, a sapiential strategy for preparing highly efficient nitrogen-deficient g-C₃N₄ featuring bunchy microtubes [R-tubular carbon nitride (TCN)] via a KOH-assisted hydrothermal treatment of rodlike melamine–cyanuric acid (RMCA) supramolecular aggregates followed by heating the reconstructed RMCA, in which KOH serves as an all-rounder for breaking hydrogen bonds, accelerating hydrolysis of melamine and nitrogen defects forming. This approach endows R-TCN with unique bunchy microtube morphology, enriched nitrogen defects, textural properties, and electronic structure, which result in narrower band gap, higher electric conductivity, more active sites, more negative conductive band, significantly increased visible light harvesting capability, and improved separation efficiency of charge carriers. As a consequence, R-TCN shows 2.44 and 39 times higher hydrogen evolution rate (8.19 μmol h^–1) than that of the pristine TCN from RMCA and bulk g-C₃N₄ from melamine. This new discovery may open a new avenue to fabricate highly efficient g-C₃N₄ catalysts

Highly-Ordered Mesoporous Carbon Nitride with Ultrahigh Surface Area and Pore Volume as a Superior Dehydrogenation Catalyst

In this work, a highly ordered mesoporous carbon nitride nanorods with 971–1124 m² g^–1 of superhigh specific surface area, 1.31–1.79 cm³ g^–1 of ultralarge pore volume, bimodal mesostructure, and 9.3–23 wt % of high N content was prepared via a facile nanocasting approach using SBA-15 as template and hexamethylenetetramine as carbon nitride precursor, and the specific surface area and pore volume as well as N content are strongly dependent on the chosen precursor and pyrolysis temperature. The as-prepared materials were well characterized by HRTEM, FESEM, XRD, BET, Raman, FT-IR, XPS, and the textural structure and morphology were confirmed. The finding breaks through the bottleneck problems for fabricating mesoporous carbon nitride with both ultrahigh surface area and super large pore volume by employing an unexplored hexamethylenetetramine as carbon nitride precursor. The current synthetic strategy can be extended to the preparation of various mesoporous carbon nitride with different textural characteristics by using diverse templates under changeable preparation conditions. The developed mesoporous carbon nitride material with 750 °C of pyrolysis temperature exhibits high superior catalytic performance, ascribed to the promoting effect of nitrogen within the carbon matrix, the rich CO group and defect/edge feature on the surface, small size of graphitic crystallite, as well as the ultrahigh surface area and pore volume. It can also be concluded that the microstructures including bulk and surface structure features and surface chemical properties of the carbon-based materials have a decisive influence on their catalytic performance. The developed material can be employed in various organic transformations such as the base-catalyzed reactions, selective oxidation, dehydrogenation, photocatalysis, and electrocatalysis as well as acting as a novel and efficient candidate for CO₂ capture, supercapacitor, purification of contaminated water, and future drug-delivery systems

Coupling Conversion of CO₂ and <i>n</i>‑Butane Over Modified ZSM-5: Incorporation of the Carbon from CO₂ into Hydrocarbon Products

The coupling reaction of CO2 and n-butane was conducted over different metal-modified (Mn, Zr, Ni, Ti, Zn) ZSM-5 catalysts. A high CO2 conversion of 26.5% and n-butane conversion of 100% with the aromatics selectivity of 69.1% was achieved at a CO2 to n-butane ratio of 0.95 over Zn/ZSM-5. CO2 addition promoted BTX & olefin selectivity, while it inhibited alkane & A9+ formation. A detailed analysis showed that 13% of the carbon atoms from CO2 were incorporated in the generation of aromatic hydrocarbons. Oxygenated intermediates, such as aliphatic alcohol, aliphatic ketones, and substituted cyclopentenones, were detected sequentially with the increase of the reaction temperature. In addition, reverse Boudouard reaction, water gas shift reaction, and dry reforming also participated in the formation of CO over Zn/ZSM-5. Based on these findings and the detailed characterization results, a plausible mechanism of direct and indirect incorporation of carbon from CO2 into aromatics was proposed for the coupling reaction

Syngas Production via Steam–CO₂ Dual Reforming of Methane over LA-Ni/ZrO₂ Catalyst Prepared by l‑Arginine Ligand-Assisted Strategy: Enhanced Activity and Stability

A highly dispersed supported nickel catalyst (LA-Ni/ZrO₂), synthesized by a facile l-arginine ligand-assisted incipient wetness impregnation (LA-IWI) approach, demonstrates much superior catalytic activity and exceptional stability for steam–CO₂ dual reforming of methane in comparison with the classical Ni/ZrO₂ catalyst by the IWI method. The origin of the enhanced activity and stability of the developed LA-Ni/ZrO₂ catalyst as well as the role of the Ni–{(l-Arg)} complex as the Ni precursor is revealed by employing diverse characterization techniques including X-ray diffraction (XRD), N₂ adsorption (BET), transmission electron microscopy (TEM), H₂ temperature-programmed reduction (H₂-TPR), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), CO chemisorption, temperature-programmed hydrogenation (TPH), and thermogravimetric analysis (TGA). The superior catalytic activity of the developed LA-Ni/ZrO₂ catalyst to the classical Ni/ZrO₂ can be ascribed to the higher Ni dispersion, intensified Ni–support interaction, the enlarged oxygen vacancies, as well as the increased <i>t</i>-ZrO₂ content and enhanced reducibility of NiO led by oxygen vacancies. More interestingly, although a larger amount of coke depositing on the spent LA-Ni/ZrO₂ catalyst in comparison with that on the spent Ni/ZrO₂ can be observed by TGA and TPH measurement, the developed LA-Ni/ZrO₂ illustrates much higher catalytic stability to Ni/ZrO₂, ascribed to the superior thermal sintering resistance of Ni nanoparticles and the different coke morphologies confirmed by TEM images led by intensified interaction of Ni and the ZrO₂ support. The much superior catalytic activity and stability of the developed LA-Ni/ZrO₂ catalyst endows it to be a promising candidate for syngas production with diverse H₂/CO ratios via steam–CO₂ dual reforming of methane

Fabrication of Isolated VO_<i>x</i> Sites on Alumina for Highly Active and Stable Non-Oxidative Dehydrogenation

The vanadium catalyst is a promising alternative to the Pt–Sn catalyst for non-oxidative dehydrogenation, but developing a highly active and stable vanadium catalyst remains a huge challenge. Herein, we report a single-site vanadium catalyst with isolated VOx species on commercial Al2O3 (0.5VOx-iso/Al2O3–salen) prepared with the salen–V complex as a precursor with the subsequential alkali washing process, showing unexpectedly high catalytic stability for non-oxidative propane dehydrogenation to propylene compared to the polyvanadium catalyst in the absence of H2 in the feed, while this process over metal catalysts is often carried out in the presence of H2 gas to mitigate catalyst deactivation. It can be found that the isolated dispersed VOx species is responsible for the surprising catalytic stability owing to its unexpectedly high coke resistance. Furthermore, through alkali washing of the supported monolayer VOx prepared by the traditional oxalic acid (OA)-assisted method, the isolated 0.5VOx-iso/Al2O3–OA can also be achieved. However, the 0.5VOx-iso/Al2O3–salen catalyst prepared by a salen-assisted method shows 4.0 times the turnover frequency value compared to 0.5VOx-iso/Al2O3–OA prepared by the OA-assisted method, ascribed to the readily reduced V5+ to low-valance V3+ and V4+ by carbon species. This work not only generates a unique single-site vanadium catalyst for propane non-oxidative dehydrogenation to propylene but also opens a new avenue for designing other promising catalysts