Single-Pd-Site Catalyst Induced by Different Dimensional Nitrogen of N-Doping Carbon for Efficient Hydroaminocarbonylation of Alkynes.

The unsaturated amides are traditionally synthesized by acylation of carboxylic acids or hydration of nitrile compounds but are rarely investigated by hydroaminocarbonylation of alkynes using heterogeneous single-metal-site catalysts (HSMSCs). Herein, single-Pd-site catalysts supported on N-doping carbon (NC) with different nitrogen dimensions inherited from corresponding metal-organic-framework precursors are successfully synthesized. 2D NC-supported single-Pd-site (Pd1/NC-2D) exhibited the best performance with near 100% selectivity and 76% yield of acrylamide for acetylene hydroaminocarbonylation with better stability, superior to those of Pd1/NC-3D, single-metal-site/nanoparticle coexisting catalyst, and nanoparticle catalyst. The coordination environment and molecular evolution of the single-Pd-site during the process of acetylene hydroaminocarbonylation on Pd1/NC-2D are detailly illuminated by various characterizations and density functional theoretical calculations (DFT). DFT also showed the energy barrier of rate-determining step on Pd1/NC-2D is lower than that of Pd1/NC-3D. Furthermore, Pd1/NC-2D catalyst illustrated the general applicability of the hydroaminocarbonylation for various alkynes.

Water-participated mild oxidation of ethane to acetaldehyde.

The direct conversion of low alkane such as ethane into high-value-added chemicals has remained a great challenge since the development of natural gas utilization. Herein, we achieve an efficient one-step conversion of ethane to C2 oxygenates on a Rh1/AC-SNI catalyst under a mild condition, which delivers a turnover frequency as high as 158.5 h-1. 18O isotope-GC-MS shows that the formation of ethanol and acetaldehyde follows two distinct pathways, where oxygen and water directly participate in the formation of ethanol and acetaldehyde, respectively. In situ formed intermediate species of oxygen radicals, hydroxyl radicals, vinyl groups, and ethyl groups are captured by laser desorption ionization/time of flight mass spectrometer. Density functional theory calculation shows that the activation barrier of the rate-determining step for acetaldehyde formation is much lower than that of ethanol, leading to the higher selectivity of acetaldehyde in all the products.

Palladium and Ruthenium Dual-Single-Atom Sites on Porous Ionic Polymers for Acetylene Dialkoxycarbonylation: Synergetic Effects Stabilize the Active Site and Increase CO Adsorption.

Heterogeneous single-metal-site catalysts usually suffer from poor stability, thereby limiting industrial applications. Dual Pd1 -Ru1 single-atom-sites supported on porous ionic polymers (Pd1 -Ru1 /PIPs) were constructed using a wetness impregnation method. The two isolated metal species in the form of a binuclear complex were immobilized on the cationic framework of PIPs through ionic bonds. Compared to the single Pd- or Ru-site catalyst, the dual single-atom system exhibits higher activity with 98 % acetylene conversion and near 100 % selectivity to dialkoxycarbonylation products, as well as better cycling stability for ten cycles without obvious decay. Based on DFT calculations, it was found that the single-Ru site exhibited a strong CO adsorption energy of -1.6 eV, leading to an increase in the local CO concentration of the catalyst. Notably, the Pd1 -Ru1 /PIPs catalyst had a much lower energy barrier of 2.49 eV compared to 3.87 eV of Pd1 /PIPs for the rate-determining step. The synergetic effect between neighboring single sites Pd1 and Ru1 not only enhanced the overall activity, but also stabilized PdII active sites. The discovery of synergetic effects between single sites can deepen our understanding of single-site catalysts at the molecular level.

Sulfur Poisoning and Self-Recovery of Single-Site Rh1 /Porous Organic Polymer Catalysts for Olefin Hydroformylation.

Sulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single-metal-site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self-recovery are first presented on an industrialized single-Rh-site catalyst (Rh1 /POPs). A decreased turnover frequency of Rh1 /POPs from 4317 h-1 to 318 h-1 was observed in a 1000 ppm H2 S co-feed for ethylene hydroformylation, but it self-recovered to 4527 h-1 after withdrawal of H2 S, whereas the rhodium nanoparticles demonstrated poor activity and self-recovery ability. H2 S reduced the charge density of the single Rh atom and lowered its Gibbs free energy with the formation of inactive (SH)Rh(CO)(PPh3 -frame)2 , which could be regenerated to active HRh(CO)(PPh3 -frame)2 after withdrawing H2 S. The mechanism and the sulfur-related structure-activity relationship were highlighted. This work provides an understanding of heterogeneous ethylene hydroformylation and sulfur-poisoned regeneration in the science of single-atom catalysts.

An efficient and ultrastable single-Rh-site catalyst on a porous organic polymer for heterogeneous hydrocarboxylation of olefins.

A heterogeneous hydrocarboxylation process of olefins to obtain carboxylic acids with one more carbon was first realized using a single-Rh-site catalyst formed on porous organic polymer (Rh1/POPs). The in situ formation of hydrophilic porous ionic polymer from hydrophobic POPs with the help of CH3I led to high activity and superb stability.

In situ formation of mononuclear complexes by reaction-induced atomic dispersion of supported noble metal nanoparticles.

Supported noble metal nanoclusters and single-metal-site catalysts are inclined to aggregate into particles, driven by the high surface-to-volume ratio. Herein, we report a general method to atomically disperse noble metal nanoparticles. The activated carbon supported nanoparticles of Ru, Rh, Pd, Ag, Ir and Pt metals with loading up to 5 wt. % are completely dispersed by reacting with CH3I and CO mixture. The dispersive process of the Rh nanoparticle is investigated in depth as an example. The in-situ detected I• radicals and CO molecules are identified to promote the breakage of Rh-Rh bonds and the formation of mononuclear complexes. The isolated Rh mononuclear complexes are immobilized by the oxygen-containing functional groups based on the effective atomic number rule. The method also provides a general strategy for the development of single-metal-site catalysts for other applications.

[Chemical constituents from the seed coat of Juglans regia].

Fifteen compounds were isolated from the seed coat of Juglans regia by silica gel, MCI gel and Sephadex LH-20 gel column chromatography, as well as high preparative performance liquid chromatography. Their structures were identified as salidroside (1), (6S, 9S)-roseoside (2), (6S, 9R)-roseoside (3), blumenol C glucoside (4), byzantionoside B (5), 5-hydroxy-2-methoxy-1, 4-naphthoquinone (6), gallic acid (7), glycerol 1-(9Z-octadecenoate)-2-(9Z, 12Z-octadecadienoate)-3-(9Z, 12Z, 15Z-octadecatrienoate) (8), glycerol 1, 2, 3-tri-(9Z, 12Z-octadecadienoate) (9), glycerol 1, 2, 3-tri-(9Z, 12Z, 15Z-octadecatrienoate) (10), glycerol 1-hexadecanoate-2, 3-di-(9Z, 12Z-octadecadienoate) (11) on the basis of EI-MS, FAB-MS and NMR spectra. Moreover, 35 volatile compounds were identified by GC-MS.