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The fabrication of noble metal free catalysts with excellent performance and high stability by a simple, efficient, general and low-cost approach remains an urgent task for solving the problem of resource shortage. Herein, Cu-based metal organic frameworks (MOFs) immobilized on commercial filter papers were used as pyrolysis precursors to synthesize CuxO@C at various calcination temperatures. Notably, the resultant CuxO@C-400 exhibits an excellent catalytic performance toward the reaction of reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). By virtue of the large specific surface area, well-developed porosity, good stability and high dispersity of CuxO nanoparticles, the obtained CuxO@C-400 could complete the reduction reaction within 11 min with a large apparent rate constant κapp value (4.8 × 10−3 s−1). Our strategy therefore opens a new avenue for the preparation of low-cost and high-performance noble metal free catalysts. [ABSTRACT FROM AUTHOR]

CuO/CeO2 catalysts were widely studied as an alternative to precious metal catalysts, and the Cu–Ce synergy was essential to improve the catalytic performance. In this paper, the effects of CuO loading on Cu–Ce synergy in CuO/CeO2 nanorod catalysts and their performance in toluene combustion were systematically investigated. It was found that non-equilibrium plasma facilitated the dispersion of CuO active species on the CeO2 surface. With the increase of the CuO loading from 1 wt% to 4 wt%, the Cu–Ce synergistic effect was gradually improved, which generated Cu+/Cu2+ and Ce3+/Ce4+ redox electron pairs. The highest oxygen vacancy concentration and Cu+ content of CuCe-4 (4 wt%) resulting from strong Cu–Ce synergy accelerated the activation of chemisorbed oxygen and consequently improved the efficiency of toluene catalytic combustion. [ABSTRACT FROM AUTHOR]

The development of a bifunctional ruthenium-based electrocatalyst that can efficiently and economically drive both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains challenging because ruthenium species can undergo severe agglomeration during preparation which can significantly reduce the catalytic activity. Constructing supported metal catalysts can not only improve the stability of Ru but also improve the catalytic performance by adjusting the electronic structure, which is an effective way to solve the current challenges. In this paper, Ru-loaded MoO2/MoO3 heterostructures (Ru–MoOx) with oxygen vacancies were successfully synthesized by controlling the annealing temperature. This special structure can effectively tune the electronic structure, enhance the electrical conductivity and increase the active sites, thus improving the catalytic activity of the catalyst. Performance studies have shown that Ru–MoOx exhibits excellent HER and OER performance in alkaline media. And it is not surprising that the overall water decomposition performance of Ru–MoOx is also excellent, requiring only a cell voltage of 1.54 V to reach 10 mA cm−2. [ABSTRACT FROM AUTHOR]

The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol has recently attracted much attention because such a process would allow the application of green chemistry principles. However, its major drawbacks lie in the high stability of CO2 and in the thermodynamic equilibrium of the reaction. The present review aims to discuss strategies that have been explored by researchers recently to improve the yield of DMC. Elaborate catalysts for the activation of CO2 and methanol, such as organometallic catalysts, ionic liquids, alkali metal catalysts, heteropolyacid catalysts, metal-supported catalysts, metal organic frameworks (MOFs) and metal oxide catalysts, are summarized and discussed in this review paper. Moreover, the significance of using a dehydrating agent for in situ water trapping during the reaction (and concomitant thermodynamic equilibrium shift), such as molecular sieves, ionic liquids, acetals, esters and nitriles, is also considered and the detailed roles of dehydrating agents in the formation of DMC are analyzed in this review. [ABSTRACT FROM AUTHOR]

The synthesis of propargylamines by traditional methods is limited by several drawbacks such as anhydrous conditions, low temperatures and by-products. A3-coupling reactions (aldehydes, amines, and alkynes), that involve a catalytic amount of metal complexes, have been recently recognized as a powerful alternative for the synthesis of these important scaffolds. In this paper, four new silver and gold complexes (3a, 4a, 3b and 4b), bearing N-heterocyclic carbene (NHC) ligands, were tested in A3-coupling reactions, combining the use of harmless metals as catalysts with sustainable reaction conditions (neat conditions or water as solvent). NHC silver(I) and gold(I) complexes were synthesized and characterized by 1H and 13C NMR spectroscopy, ESI-MS and elemental analysis. The molecular structure of the NHC gold(I) complex 4b was determined by single crystal X-ray diffraction. A comparison of the catalytic behavior in A3-coupling reactions among the synthesized complexes disclosed the higher efficiency of gold catalysts. Computational studies shed light on species possibly involved in the catalytic mechanism. [ABSTRACT FROM AUTHOR]

Precious metal nanoparticles (NPs) are attractive for use in the field of catalysis because of their precisely controlled sizes and shapes. However, NPs exhibit insufficient anti-sintering properties under common operating conditions due to their poor thermal stability at elevated temperatures. In this paper, the preparation of noble metallic NPs (Pd and Au) incorporated inside the pores of an SBA-15 support via a sol-immobilization method, which prevents their aggregation, is reported. The Pd NPs retain their size of ∼5 nm within the channels of SBA-15, even after aging at 800 °C for three days under an air atmosphere. However, Au NPs aggregated at a temperature of calcination above 500 °C. Using a set of characterization methods comprising XRD, STEM, HRTEM, TPR, and DRIFTS analysis, it is revealed that Pd on SBA-15 exhibits better anti-sintering properties than the Au supported system. The catalytic activity and durability of M/SBA-15 (M: Pd or Au) catalysts were studied using CO oxidation with and without steam (10 vol%). Interestingly, a hydrothermally treated (Pd/SBA-15-750-H2O-3d) catalyst leads to the partial re-dispersion of Pd. This helps to attain smaller particles of ∼1.6 nm, which play a prominent role in the catalytic performance. This work provides insight into the design of sintering-resistant metal catalysts, which would be suitable for industrial applications under harsh conditions. [ABSTRACT FROM AUTHOR]

Graphdiyne (GDY), a novel two-dimensional (2D) carbon material with sp- and sp2-hybridized carbon atoms, has earned a lot of attention in recent years. Owing to its low reduction potential and highly conjugated electronic structure, it can be used as a reducing agent and stabilizer for the electroless deposition of highly dispersed Au nanoparticles. In this paper, we observe that exfoliated GDY (eGDY), the exfoliation of bulk GDY into single- or few-layered GDY in aqueous solution, can be used as an excellent substrate for the electroless deposition of very small Au nanoparticles to form a Au/eGDY nanocomposite that exhibits higher catalytic performance for the reduction of 4-nitrophenol. The higher catalytic performance is considered to arise from the high specific surface area of eGDY and the electroless deposition of active metal catalysts with eGDY as the support. Our results inspired the present investigation into the use of eGDY for the development of highly efficient catalysts. [ABSTRACT FROM AUTHOR]

para-Xylene (PX) is a basic building block of polyethylene terephthalate, which is currently produced from petroleum resources. Developing a renewable route to PX is highly desirable to address both economic and environmental concerns. Several attempts used noble metal catalysts, e.g. Pd/Al2O3, to synthesize PX from biomass-derived 4-methyl-3-cyclohexene-1-carboxaldehyde (4-MCHCA), but suffered from a severe decarbonylation reaction, resulting in toluene as the main product. In this paper, we report an FeOx modification strategy to suppress the decarbonylation reaction on a Pd/Al2O3 catalyst, leading to a drastic shift in selectivity towards PX with a yield up to 81% via a cascade dehydroaromatization–hydrodeoxygenation (DHA–HDO) pathway. Characterization and control experiments revealed that the electron density of Pd sites decreased in an FeOx-modified Pd/Al2O3 catalyst compared to Pd/Al2O3, thus tuning the preferential adsorption mode of the substrate from η2-(C,O), the key transition state of the decarbonylation reaction, to the η1-(O) mode that favors the hydrodeoxygenation process. Notably, this designed catalyst is highly stable and is readily applicable in the selective synthesis of a broad range of desired aromatic chemicals via the same DHA–HDO pathway from cyclohex-3-enecarbaldehyde derivatives. Overall, this work develops a controllable catalyst modification strategy that tailors an efficient catalyst for petroleum-independent bio-PX synthesis. [ABSTRACT FROM AUTHOR]

MoS2-based nanomaterials are considered promising effective electrocatalysts to replace precious metal catalysts for hydrogen evolution reaction. However, understanding the effect of MoO2 in MoS2-based catalysts for hydrogen evolution reaction is ambiguous. In this paper, MoS2 nanoflowers of 210–430 nm in diameter were hydrothermally synthesized by the reduction of α-MoO3 particles with KSCN in a hydrochloric acid medium. Similarly, MoO2–MoS2-B nanoflowers and MoO2–MoS2-R nanoflowers were fabricated using α-MoO3 nanobelts and h-MoO3 microrods as Mo sources, respectively. Systematic studies on synthetic parameters verified that the formation of MoS2 nanoflowers is favored with high acidity, low MoO3/KSCN ratio and high temperature. The resultant nanoflowers served as electrocatalysts to drive hydrogen evolution in acidic solution. The MoS2 nanoflowers showed a relatively higher activity with a potential of 256 mV at 10 mA cm−2 compared to MoO2–MoS2-B nanoflowers (283 mV) and MoO2–MoS2-R nanoflowers (305 mV). Furthermore, MoS2 nanoflower catalysts maintained high stability after 1000 cycles and long-term durability for 5 h. The high catalytic activity could be ascribed to the large exposure of the Mo–S species and small amounts of Mo–O species on the MoS2-based catalyst surface. [ABSTRACT FROM AUTHOR]

This paper demonstrated the feasibility of conducting an enzymatic ring-opening polymerisation by reactive extrusion (REX) at high shear and temperature conditions. Using immobilized Candida antarctica Lipase B (CALB) as catalyst at temperatures ranging from 90 to 130 °C, ̉-pentadecalactone (PDL) was converted (＞99%) by REX at 60 RPM for 15 min to PPDL with ≥Mw 163 000 g mol−1. [ABSTRACT FROM AUTHOR]