复合催化剂上CO2加氢合成C2烃类

介绍了由CO₂+H₂合成C2⁺烃的几种复合催化剂体系的研究进展，比较和评价了复合催化剂体系的活性和选择性及对C2⁺烃类生成的影响。着重于复合催化剂体系对C4⁺烃的生成及产物分布的影响并简述反应机理。     

Partially Oxidized Palladium Nanodots for Enhanced Electrocatalytic Carbon Dioxide Reduction

Here we report a partially oxidized palladium nanodot (Pd/PdO_x) catalyst with a diameter of around 4.5 nm. In aqueous CO₂‐saturated 0.5 m KHCO₃, the catalyst displays a Faradaic efficiency (FE) of 90 % at −0.55 V vs. reversible hydrogen electrode (RHE) for carbon monoxide (CO) production, and the activity can be retained for at least 24 h. The improved catalytic activity can be attributed to the strong adsorption of CO₂^.− intermediate on the Pd/PdO_x electrode, wherein the presence of Pd²⁺ during the electroreduction reaction of CO₂ may play an important role in accelerating the carbon dioxide reduction reaction (CO₂RR). This study explores the catalytic mechanism of a partially oxidized nanostructured Pd electrocatalyst and provides new opportunities for improving the CO₂RR performance of metal systems.     

Carbon Dioxide as a Raw Material: The Synthesis of Formic Acid and Its Derivatives from CO2

The use of carbon dioxide as a raw material for chemical syntheses is an ecologically and economically valuable extension to the carbon sources used at the present time. In order to convert the thermodynamically stable and comparatively unreactive CO₂ molecule into the desired product in an efficient manner, suitable reaction conditions and activation mechanisms must be found. The catalytic reduction of CO₂ to formic acid and its derivatives has been intensively studied in recent years. A number of new approaches to the synthesis of formic acid from CO₂ have reached such a state of knowledge that continuing development may well lead to industrial-scale operation in the near future. This can to a large extent be attributed to the fruitful interaction between investigative work into reaction mechanisms and the development of new catalytic systems.     

Coupling Mo2C with Nitrogen‐Rich Nanocarbon Leads to Efficient Hydrogen‐Evolution Electrocatalytic Sites

In our efforts to obtain electrocatalysts with improved activity for water splitting, meticulous design and synthesis of the active sites of the electrocatalysts and deciphering how exactly they catalyze the reaction are vitally necessary. Herein, we report a one‐step facile synthesis of a novel precious‐metal‐free hydrogen‐evolution nanoelectrocatalyst, dubbed Mo₂C@NC that is composed of ultrasmall molybdenum carbide (Mo₂C) nanoparticles embedded within nitrogen‐rich carbon (NC) nanolayers. The Mo₂C@NC hybrid nanoelectrocatalyst shows remarkable catalytic activity, has great durability, and gives about 100 % Faradaic yield toward the hydrogen‐evolution reaction (HER) over a wide pH range (pH 0–14). Theoretical calculations show that the Mo₂C and N dopants in the material synergistically co‐activate adjacent C atoms on the carbon nanolayers, creating superactive nonmetallic catalytic sites for HER that are more active than those in the constituents.     

Bifunctional Onium and Potassium Iodides as Nucleophilic Catalysts for the Solvent-Free Syntheses of Carbonates,Thiocarbonates, and Oxazolidinones from Epoxides

The catalytic potential of organo-onium iodides as nucleophilic catalysts is aptly demonstrated in the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO₂), as a representative CO₂ utilization reaction. Although organo-onium iodide nucleophilic catalysts are metal-free environmentally benign catalysts, harsh reaction conditions are generally required to efficiently promote the coupling reactions of epoxides and CO₂. To solve this problem and accomplish efficient CO₂ utilization reactions under mild conditions, bifunctional onium iodide nucleophilic catalysts bearing a hydrogen bond donor moiety were developed by our research group. Based on the successful bifunctional design of the onium iodide catalysts, nucleophilic catalysis using a potassium iodide (KI)-tetraethylene glycol complex was also investigated in coupling reactions of epoxides and CO₂ under mild reaction conditions. These effective bifunctional onium and potassium iodide nucleophilic catalysts were applied to the solvent-free syntheses of 2-oxazolidinones and cyclic thiocarbonates from epoxides.     

Photoreduction of carbon dioxide by hydrogen and methane

Zirconium oxide is active for photoreduction of gaseous carbon dioxide to carbon monoxide with hydrogen. A stable surface species arises under the photoreduction of CO₂ on zirconium oxide, and it is identified as surface formate by infrared spectroscopy. Adsorbed CO₂ is converted to formate by photoreaction with hydrogen. The surface formate is a true reaction intermediate since CO is formed by the photoreaction of formate and CO₂; surface formate works as a reductant of carbon dioxide to yield carbon monoxide. The dependence on the wavelength of irradiation light shows that a bulk ZrO₂ is not a photoactive species. When ZrO₂ adsorbs CO₂ a new band appears in photoluminescence excitation spectrum. The photoactive species in the reaction that CO₂+H₂ yields HCOO⁻ is presumably formed by the adsorption of CO₂ on ZrO₂ surface. Hydrogen molecules play a role to supply an atomic hydrogen. Therefore, methane molecules can also be used as a reductant of carbon dioxide.     

Ruthenium-Catalyzed Synthesis of Cyclic and Linear Acetals by the Combined Utilization of CO2, H2, and Biomass Derived Diols

Herein a transition-metal catalyst system for the selective synthesis of cyclic and linear acetals from the combined utilization of carbon dioxide, molecular hydrogen, and biomass derived diols is presented. Detailed investigations on the substrate scope enabled the selectivity of the reaction to be largely guided and demonstrated the possibility of integrating a broad variety of substrate molecules. This approach allowed a change between the favored formation of cyclic acetals and linear acetals, originating from the bridging of two diols with a carbon-dioxide based methylene unit. This new synthesis option paves the way to novel fuels, solvents, or polymer building blocks, by the recently established “bio-hybrid” approach of integrating renewable energy, carbon dioxide, and biomass in a direct catalytic transformation.     

The phase behavior of fluorinated diols,divinyl adipate and a fluorinated polyester in supercritical carbon dioxide

The use of supercritical carbon dioxide as a reaction medium for polyester synthesis is hindered by the low solubility of diols in CO₂. However, it has been previously demonstrated that fluorinated compounds can exhibit greater miscibility with carbon dioxide than their hydrocarbon analogs. Therefore, the phase behavior of fluorinated diols and divinyl adipate (DVA), an activated diester, in supercritical carbon dioxide has been investigated at 323 K. The phase behavior of equimolar mixtures of DVA with the most carbon dioxide-soluble diol, 3,3,4,4,5,5,6,6-octafluorooctan-1,8-diol (OFOD), was also determined. The solubility of a polyester synthesized from DVA and 2,2,3,3-tetrafluoro-1,4-butanediol (TFBD) was found to be less CO₂-soluble than its monomers. DVA was much more soluble in CO₂ than any of the fluorinated diols, therefore, no attempt was made to fluorinate the DVA structure. Because both substrates and polyester product were soluble in carbon dioxide, the enzymatic synthesis of a fluorinated polyester from DVA and octafluorooctandiol was performed in supercritical carbon dioxide, resulting in a polymer with a weight average molecular weight of 8232 Da.     

Effect of a modifying additive to a rhodium-containing catalyst on the kinetics of CO<Subscript>2</Subscript> hydrogenation

A study was carried out on the kinetics of the hydrogenation of carbon dioxide to give methane in the presence of supported rhodium catalysts with additives of Cr, Fe, Co, Mo, Pt, Sn, and Pb compounds. The modifying additives were shown to have a significant effect on the energy characteristics of the carbon dioxide hydrogenation reaction. The introduction of a metal additive into Rh/Al₂O₃ leads to an increase in the bond energy of the rhodium 3d_5/2 electrons and, thus, to a positive charge on the rhodium particles and increase in the heat of hydrogen adsorption. In turn, the change in the heat of hydrogen adsorption significantly affects the specific catalytic activity of the catalysts studied.     

Role of Ligand in the Selective Production of Hydrogen from Formic Acid Catalysed by the Mononuclear Cationic Zinc Complexes [(L)Zn(H)]+ (L=tpy,phen, and bpy)

A series of zinc-based catalysts was evaluated for their efficiency in decomposing formic acid into molecular hydrogen and carbon dioxide in the gas phase using quadrupole ion trap mass spectrometry experiments. The effectiveness of the catalysts in the series [(L)Zn(H)]⁺, where L=2,2′:6′,2′′-terpyridine (tpy), 1,10-phenanthroline (phen) or 2,2′-bipyrydine (bpy), was found to depend on the ligand used, which turned out to be fundamental in tuning the catalytic properties of the zinc complex. Specifically, [(tpy)Zn(H)]⁺ displayed the fastest reaction with formic acid proceeding by dehydrogenation to produce the zinc formate complex [(tpy)Zn(O₂CH)]⁺ and H₂. The catalysts [(L)Zn(H)]⁺ are reformed by decarboxylating the zinc formate complexes [(L)Zn(O₂CH)]⁺ by collision-induced dissociation, which is the only reaction channel for each of the ligands used. The decarboxylation reaction was found to be reversible, since the zinc hydride complexes [(L)Zn(H)]⁺ react with carbon dioxide yielding the zinc formate complex. This reaction was again substantially faster for L=tpy than L=phen or bpy. The energetics and mechanisms of these processes were modelled using several levels of density functional theory (DFT) calculations. Experimental results are fully supported by the computational predictions.     

Cesium carbonate catalyzed efficient synthesis of quinazoline-2,4(1H,3H)-diones using carbon dioxide and 2-aminobenzonitriles

Abstract

An efficient protocol for the synthesis of quinazoline-2,4(1H,3H)-diones derivatives from 2-aminobenzonitriles with carbon dioxide using catalytic amount of cesium carbonate has been developed. 6,7-Dimethoxyquinazoline-2,4(1H,3H)-dione, which is one of the key intermediate for the synthesis of several drugs (Prazosin, Bunazosin and Doxazosin) was synthesized. The effect of different reaction parameters like influences of bases, solvent, temperature, CO₂ pressure and reaction time were investigated for the title reaction.     

Solvent Impedes CO2 Cycloaddition on Metal–Organic Frameworks

The catalytic performance of metal–organic frameworks (MOFs) for the synthesis of cyclic carbonate from carbon dioxide and epoxides has been explored under solvent and solvent‐free conditions, respectively. It was found that MOF catalysts have significantly improved catalytic activities in solvent‐free CO₂ cycloaddition reactions than those in solvent. The mechanism was discussed with regard to the competition of solvent with substrate to adhere MOF catalysts during the reaction process.     

A Bimetallic Zn/Fe Polyphthalocyanine‐Derived Single‐Atom Fe‐N4 Catalytic Site:A Superior Trifunctional Catalyst for Overall Water Splitting and Zn–Air Batteries

Developing an efficient single‐atom material (SAM) synthesis and exploring the energy‐related catalytic reaction are important but still challenging. A polymerization–pyrolysis–evaporation (PPE) strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N₄ catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe‐N₄ site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn–air battery devices containing the Fe‐N₄ SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.     

Bimetallic systems containing Fe, Co, Ni, and Mn nanoparticles as catalysts for the hydrogenation of carbon oxides

The hydrogenation reaction of carbon dioxide and a mixture of carbon oxides on bimetallic catalytic systems containing nanoparticles of Fe, Ni, Co, and Mn supported on an inert carrier is studied. It is found that the ratio of saturated and unsaturated hydrocarbons in the hydrogenation products and the synergistic effect are determined mainly by the number of hydrogen atoms that are capable of migrating from one active center to another and by composition of those centers. Differences in the catalytic activity and selectivity of the bimetallic samples are explained by different rates of the spillover of weakly bound hydrogen (H_I) and the different rates of the jumpover of CH _x radicals from one center to another at which their further hydrogenation takes place.     

Contribution of the ligand to the electroreduction of CO2 catalyzed by a cobalt(II) macrocyclic complex

The electrochemical reduction of carbon dioxide using hexa-aza-macrocycles derived from the condensation of 1,10-phenanthroline and its Co(II) complex as an electrocatalyst dissolved in dimethylformamide has been studied by cyclic voltammetry and UV-visible spectroscopy. The ligand does not show catalytic activity and only generates hydrogen when it is reduced under carbon dioxide. The cobalt complex shows electrocatalytic activity toward the reduction of carbon dioxide, generating carbon monoxide and formic acid. Cyclic voltammetry and UV-visible spectroscopy show that the active site for the reduction is the metal center in oxidation state (I), although the reduced cobalt center alone is not enough to promote reduction of the carbon dioxide. Electrolysis at controlled potential shows that only at potentials corresponding to reduction of the ligand (second reduction) does carbon dioxide reduction occur. Cobalt(I) probably reacts with CO₂ forming a non-isolated intermediate which, when reduced, gives CO and formic acid. The second reduction that takes place on the ligand regenerates the catalyst and gives products, thus becoming the rate-determining step of the reaction.     

Tailor‐made Molecular Cobalt Catalyst System for the Selective Transformation of Carbon Dioxide to Dialkoxymethane Ethers

Herein a non‐precious transition‐metal catalyst system for the selective synthesis of dialkoxymethane ethers from carbon dioxide and molecular hydrogen is presented. The development of a tailored catalyst system based on cobalt salts in combination with selected Triphos ligands and acidic co‐catalysts enabled a synthetic pathway, avoiding the oxidation of methanol to attain the formaldehyde level of the central CH₂ unit. This unprecedented productivity based on the molecular cobalt catalyst is the first example of a non‐precious transition‐metal system for this transformation utilizing renewable carbon dioxide sources.     

Carbon monoxide and hydrogen (syngas) as a C1-building block for selective catalytic methylation

A catalytic reaction using syngas (CO/H₂) as feedstock for the selective β-methylation of alcohols was developed whereby carbon monoxide acts as a C1 source and hydrogen gas as a reducing agent. The overall transformation occurs through an intricate network of metal-catalyzed and base-mediated reactions. The molecular complex [Mn(CO)₂Br[HN(C₂H₄PⁱPr₂)₂]] 1 comprising earth-abundant manganese acts as the metal component in the catalytic system enabling the generation of formaldehyde from syngas in a synthetically useful reaction. This new syngas conversion opens pathways to install methyl branches at sp³ carbon centers utilizing renewable feedstocks and energy for the synthesis of biologically active compounds, fine chemicals, and advanced biofuels.

A broadly applicable catalytic process for the selective β-methylation of alcohols is presented using syngas (CO/H₂) directly as a C1 building block and the shown manganese complex in the presence of a base as the catalytic system.     

Remarkable carbon dioxide catalytic capture (CDCC) leading to solid-form carbon material via a new CVD integrated process (CVD-IP): An alternative route for CO2 sequestration

Through our newly-developed “chemical vapor deposition integrated process (CVD-IP)” using carbon dioxide (CO₂) as the raw material and only carbon source introduced, CO₂ could be catalytically activated and converted to a new solid-form product, i.e., carbon nanotubes (CO₂-derived) at a quite high yield (the single-pass carbon yield in the solid-form carbon-product produced from CO₂ catalytic capture and conversion was more than 30% at a single-pass carbon-base). For comparison, when only pure carbon dioxide was introduced using the conventional CVD method without integrated process, no solid-form carbon-material product could be formed. In the addition of saturated steam at room temperature in the feed for CVD, there were much more end-opening carbon nano-tubes produced, at a slightly higher carbon yield. These inspiring works opened a remarkable and alternative new approach for carbon dioxide catalytic capture to solid-form product, comparing with that of CO₂ sequestration (CCS) or CO₂ mineralization (solidification), etc. As a result, there was much less body volume and almost no greenhouse effect for this solid-form carbon-material than those of primitive carbon dioxide.     

The Origin of the Catalytic Activity of a Metal Hydride in CO2 Reduction

Atomic hydrogen on the surface of a metal with high hydrogen solubility is of particular interest for the hydrogenation of carbon dioxide. In a mixture of hydrogen and carbon dioxide, methane was markedly formed on the metal hydride ZrCoH_x in the course of the hydrogen desorption and not on the pristine intermetallic. The surface analysis was performed by means of time‐of‐flight secondary ion mass spectroscopy and near‐ambient pressure X‐ray photoelectron spectroscopy, for the in situ analysis. The aim was to elucidate the origin of the catalytic activity of the metal hydride. Since at the initial stage the dissociation of impinging hydrogen molecules is hindered by a high activation barrier of the oxidised surface, the atomic hydrogen flux from the metal hydride is crucial for the reduction of carbon dioxide and surface oxides at interfacial sites.     

Mesoporous Rh Emerging from Nanophase‐separated Rh‐Y Alloy

Mesoporous precious metals with abundant active sites and high surface area have been widely recognized as high‐performance catalytic materials. However, the templated synthesis is complex and costly. Herein, we report a mesoporous rhodium (m‐Rh) that can be readily synthesized from entangled nanofibres of Rh and Y₂O₃ without templates. The entangled nanofibres, prepared from uniform Rh‐Y alloys under redox atmosphere, were the key precursor in the synthesis processes. Moreover, the m‐Rh efficiently catalyzed carbon dioxide reforming of methane (DRM) at a low reaction temperature of 683 K. Further, electrochemical methods of CO electro‐oxidation were innovatively used to demonstrate the stability of CO and oxygen species for the DRM reaction.