The Cu–ZnO synergy in methanol synthesis from CO2, Part 1: Origin of active site explained by experimental studies and a sphere contact quantification model on Cu + ZnO mechanical mixtures

Tuning Catalytic Activity of CO2 Hydrogenation to C1 Product via Metal Support Interaction Over Metal/Metal Oxide Supported Catalysts

The metal supported catalysts are emerging catalysts that are receiving a lot of attention in CO2 hydrogenation to C1 products. Numerous experiments have demonstrated that the support (usually an oxide) is crucial for the catalytic performance. The support metal oxides are used to aid in the homogeneous dispersion of metal particles, prevent agglomeration, and control morphology owing to the metal support interaction (MSI). MSI can efficiently optimize the structural and electronic properties of catalysts and tune the conversion of key reaction intermediates involved in CO2 hydrogenation, thereby enhancing the catalytic performance. There is an increasing attention is being paid to the promotion effects in the catalytic CO2 hydrogenation process. However, a systematically understanding about the effects of MSI on CO2 hydrogenation to C1 products catalytic performance has not been fully studied yet due to the diversities in catalysts and reaction conditions. Hence, the characteristics and modes of MSI in CO2 hydrogenation to C1 products are elaborated in detail in our work.

Confinement Effects in Well-Defined Metal-Organic Frameworks (MOFs) for Selective CO2 Hydrogenation: A Review

Decarbonization has become an urgent affair to restrain global warming. CO₂ hydrogenation coupled with H₂ derived from water electrolysis is considered a promising route to mitigate the negative impact of carbon emission and also promote the application of hydrogen. It is of great significance to develop catalysts with excellent performance and large-scale implementation. In the past decades, metal-organic frameworks (MOFs) have been widely involved in the rational design of catalysts for CO₂ hydrogenation due to their high surface areas, tunable porosities, well-ordered pore structures, and diversities in metals and functional groups. Confinement effects in MOFs or MOF-derived materials have been reported to promote the stability of CO₂ hydrogenation catalysts, such as molecular complexes of immobilization effect, active sites in size effect, stabilization in the encapsulation effect, and electron transfer and interfacial catalysis in the synergistic effect. This review attempts to summarize the progress of MOF-based CO₂ hydrogenation catalysts up to now, and demonstrate the synthetic strategies, unique features, and enhancement mechanisms compared with traditionally supported catalysts. Great emphasis will be placed on various confinement effects in CO₂ hydrogenation. The challenges and opportunities in precise design, synthesis, and applications of MOF-confined catalysis for CO₂ hydrogenation are also summarized.

Performance of Cu/ZnO Nanosheets on Electrospun Al2O3 Nanofibers in CO2 Catalytic Hydrogenation to Methanol and Dimethyl Ether

The synthesis of methanol and dimethyl ether (DME) from carbon dioxide (CO₂) and green hydrogen (H₂) offers a sustainable pathway to convert CO₂ emissions into value-added products. This heterogeneous catalytic reaction often uses copper (Cu) catalysts due to their low cost compared with their noble metal analogs. Nevertheless, improving the activity and selectivity of these Cu catalysts for these products is highly desirable. In the present study, a new architecture of Cu- and Cu/Zn-based catalysts supported on electrospun alumina nanofibers were synthesized. The catalysts were tested under various reaction conditions using high-throughput equipment to highlight the role of the hierarchical fibrous structure on the reaction activity and selectivity. The Cu or Cu/ZnO formed a unique structure of nanosheets, covering the alumina fiber surface. This exceptional morphology provides a large surface area, up to ~300 m²/g, accessible for reaction. Maximal production of methanol (~1106 g_methanolKg_Cu^-1∙h^-1) and DME (760 g_DMEKg_Cu^-1∙h^-1) were obtained for catalysts containing 7% wt. Cu/Zn with a weight ratio of 2.3 Zn to Cu (at 300 °C, 50 bar). The promising results in CO₂ hydrogenation to methanol and DME obtained here point out the significant advantage of nanofiber-based catalysts in heterogeneous catalysis.

Carbon Dioxide Conversion on Supported Metal Nanoparticles: A Brief Review

The increasing concentration of anthropogenic CO2 in the air is one of the main causes of global warming. The Paris Agreement at COP 21 aims to reach the global peak of greenhouse gas emissions in the second half of this century, with CO2 conversion towards valuable added compounds being one of the main strategies, especially in the field of heterogeneous catalysis. In the current search for new catalysts, the deposition of metallic nanoparticles (NPs) supported on metal oxides and metal carbide surfaces paves the way to new catalytic solutions. This review provides a comprehensive description and analysis of the relevant literature on the utilization of metal-supported NPs as catalysts for CO2 conversion to useful chemicals and propose that the next catalysts generation can be led by single-metal-atom deposition, since in general, small metal particles enhance the catalytic activity. Among the range of potential indicators of catalytic activity and selectivity, the relevance of NPs’ size, the strong metal–support interactions, and the formation of vacancies on the support are exhaustively discussed from experimental and computational perspective.

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides

The inevitable emission of carbon dioxide (CO₂ ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO₂ transformations into commodity chemicals are a favorable approach in the CO₂ mitigation strategy. Among these transformations, selective hydrogenation of CO₂ to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO₂ adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO₂ adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO₂ binding modes, mechanistic studies, effects of dopant on CO₂ adsorption, and carbon/metal ratio in the CO₂ hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO₂ hydrogenation reactions.

Recent Application of Core-Shell Nanostructured Catalysts for CO2 Thermocatalytic Conversion Processes

Carbon-intensive industries must deem carbon capture, utilization, and storage initiatives to mitigate rising CO₂ concentration by 2050. A 45% national reduction in CO₂ emissions has been projected by government to realize net zero carbon in 2030. CO₂ utilization is the prominent solution to curb not only CO₂ but other greenhouse gases, such as methane, on a large scale. For decades, thermocatalytic CO₂ conversions into clean fuels and specialty chemicals through catalytic CO₂ hydrogenation and CO₂ reforming using green hydrogen and pure methane sources have been under scrutiny. However, these processes are still immature for industrial applications because of their thermodynamic and kinetic limitations caused by rapid catalyst deactivation due to fouling, sintering, and poisoning under harsh conditions. Therefore, a key research focus on thermocatalytic CO₂ conversion is to develop high-performance and selective catalysts even at low temperatures while suppressing side reactions. Conventional catalysts suffer from a lack of precise structural control, which is detrimental toward selectivity, activity, and stability. Core-shell is a recently emerged nanomaterial that offers confinement effect to preserve multiple functionalities from sintering in CO₂ conversions. Substantial progress has been achieved to implement core-shell in direct or indirect thermocatalytic CO₂ reactions, such as methanation, methanol synthesis, Fischer-Tropsch synthesis, and dry reforming methane. However, cost-effective and simple synthesis methods and feasible mechanisms on core-shell catalysts remain to be developed. This review provides insights into recent works on core-shell catalysts for thermocatalytic CO₂ conversion into syngas and fuels.

Insight into the Nature of the ZnO x Promoter during Methanol Synthesis

Despite the great commercial relevance of zinc-promoted copper catalysts for methanol synthesis, the nature of the Cu-ZnO _x synergy and the nature of the active Zn-based promoter species under industrially relevant conditions are still a topic of vivid debate. Detailed characterization of the chemical speciation of any promoter under high-pressure working conditions is challenging but specifically hampered by the large fraction of Zn spectator species bound to the oxidic catalyst support. We present the use of weakly interacting graphitic carbon supports as a tool to study the active speciation of the Zn promoter phase that is in close contact with the Cu nanoparticles using time-resolved X-ray absorption spectroscopy under working conditions. Without an oxidic support, much fewer Zn species need to be added for maximum catalyst activity. A 5-15 min exposure to 1 bar H₂ at 543 K only slightly reduces the Zn(II), but exposure for several hours to 20 bar H₂/CO and/or H₂/CO/CO₂ leads to an average Zn oxidation number of +(0.5-0.6), only slightly increasing to +0.8 in a 20 bar H₂/CO₂ feed. This means that most of the added Zn is in a zerovalent oxidation state during methanol synthesis conditions. The Zn average coordination number is 8, showing that this phase is not at the surface but surrounded by other metal atoms (whether Zn or Cu), and indicating that the Zn diffuses into the Cu nanoparticles under reaction conditions. The time scale of this process corresponds to that of the generally observed activation period for these catalysts. These results reveal the speciation of the relevant Zn promoter species under methanol synthesis conditions and, more generally, present the use of weakly interacting graphitic supports as an important strategy to avoid excessive spectator species, thereby allowing us to study the nature of relevant promoter species.

The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst

The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO₂/CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO₂/CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO₂ gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO₂ methanol synthesis.

CO2 Conversion to Alcohols over Cu/ZnO Catalysts: Prospective Synergies between Electrocatalytic and Thermocatalytic Routes

The development of efficient catalysts is one of the main challenges in CO₂ conversion to valuable chemicals and fuels. Herein, inspired by the knowledge of the thermocatalytic (TC) processes, Cu/ZnO and bare Cu catalysts enriched with Cu⁺¹ were studied to convert CO₂ via the electrocatalytic (EC) pathway. Integrating Cu with ZnO (a CO-generation catalyst) is a strategy explored in the EC CO₂ reduction to reduce the kinetic barrier and enhance C-C coupling to obtain C₂₊ chemicals and energy carriers. Herein, ethanol was produced with the Cu/ZnO catalyst, reaching a productivity of about 5.27 mmol·g_cat^-1·h^-1 in a liquid-phase configuration at ambient conditions. In contrast, bare copper preferentially produced C₁ products like formate and methanol. During CO₂ hydrogenation, a methanol selectivity close to 100% was achieved with the Cu/ZnO catalysts at 200 °C, a value that decreased at higher temperatures (i.e., 23% at 300 °C) because of thermodynamic limitations. The methanol productivity increased to approximately 1.4 mmol·g_cat^-1·h^-1 at 300 °C. Ex situ characterizations after testing confirmed the potential of adding ZnO in Cu-based materials to stabilize the Cu¹⁺/Cu⁰ interface at the electrocatalyst surface because of Zn and O enrichment by an amorphous zinc oxide matrix; while in the TC process, Cu⁰ and crystalline ZnO prevailed under CO₂ hydrogenation conditions. It is envisioned that the lower *CO binding energy at the Cu⁰ catalyst surface in the TC process than in the Cu¹⁺ present in the EC one leads to preferential CO and methanol production in the TC system. Instead, our EC results revealed that an optimum local CO production at the ZnO surface in tandem with a high amount of superficial Cu¹⁺ + Cu⁰ species induces ethanol formation by ensuring an appropriate local amount of *CO intermediates and their further dimerization to generate C₂₊ products. Optimizing the ZnO loading on Cu is proposed to tune the catalyst surface properties and the formation of more reduced CO₂ conversion products.

Copper–zinc oxide interface as a methanol-selective structure in Cu–ZnO catalyst during catalytic hydrogenation of carbon dioxide to methanol

The proper contact of zinc oxide and copper phases is essential achieving high activity/selectivity toward methanol in the Cu–ZnO system.

Understanding of the Key Factors Determining the Activity and Selectivity of CuZn Catalysts in Hydrogenolysis of Alkyl Esters to Alcohols

CuZn catalysts are perspective catalysts for esters hydrogenolysis, but more knowledge is needed to optimize their catalytic performance. In this work, we consider the impact of CuZn catalysts composition on their structure, activity, selectivity, and stability in esters hydrogenolysis. Four catalysts with various Cu/Zn ratio were synthesized by a co-precipitation and characterized in as-prepared, calcined, reduced, and spent state by XRF, XRD, N2 physisorption, CO2-TPD, NH3-TPD, and N2O chemisorption. XRD data revealed the effect of the composition on the size of Cu and ZnO particles. The catalytic performance was investigated using an autoclave. All catalysts exhibited high methyl hexanoate conversion about 48–60% after 3 h but their activity and selectivity were found to be dependent on Cu/Zn ratio. The conversion of methyl hexanoate and hexyl hexanoate was compared to explain the observed product selectivity. Moreover, the catalysts stability was investigated in three consecutive reaction cycles and correlated with changes in the size of constituent particles. Moreover, when different esters were tested, a slight decrease in conversion and increase in alcohol selectivity with a growth in molecule size was observed. Obtained results allow making a conclusion about the optimal composition that provides the good performance of CuZn catalysts in ester hydrogenolysis.

Hydride species on oxide catalysts

Hydride species on oxide catalysts are widely involved in oxide-catalyzed reactions, and relevant fundamental understanding is important to establish reaction mechanisms and structure-performance relations of oxide catalysts. In this topical review, recent progresses on the formation and reactivity of hydride species on the surface or in the bulk of oxides are briefly summarized. Firstly, characterization techniques for hydride species are introduced. Secondly, formation of hydride species on the surface or in the bulk of various oxides and their reactivity in oxide-catalyzed hydrogenation and dehydrogenation reactions are reviewed. Finally, short summary and outlook are given.

Highlights and challenges in the selective reduction of carbon dioxide to methanol

Carbon dioxide (CO₂) is the iconic greenhouse gas and the major factor driving present global climate change, incentivizing its capture and recycling into valuable products and fuels. The 6H⁺/6e^- reduction of CO₂ affords CH₃OH, a key compound that is a fuel and a platform molecule. In this Review, we compare different routes for CO₂ reduction to CH₃OH, namely, heterogeneous and homogeneous catalytic hydrogenation, as well as enzymatic catalysis, photocatalysis and electrocatalysis. We describe the leading catalysts and the conditions under which they operate, and then consider their advantages and drawbacks in terms of selectivity, productivity, stability, operating conditions, cost and technical readiness. At present, heterogeneous hydrogenation catalysis and electrocatalysis have the greatest promise for large-scale CO₂ reduction to CH₃OH. The availability and price of sustainable electricity appear to be essential prerequisites for efficient CH₃OH synthesis.

Influence of a Cu-zirconia interface structure on CO2 adsorption and activation

CO₂ adsorption and activation on a catalyst are key elementary steps for CO₂ conversion to various valuable products. In the present computational study, we screened different Cu-ZrO₂ interface structures and analyzed the influence of the interface structure on CO₂ binding strength using density functional theory calculations. Our results demonstrate that a Cu nanorod favors one position on both tetragonal and monoclinic ZrO₂ surfaces, where the bottom Cu atoms are placed close to the lattice oxygens. In agreement with previous calculations, we find that CO₂ prefers a bent bidentate configuration at the Cu-ZrO₂ interface and the molecule is clearly activated being negatively charged. Straining of the Cu nanorod influences CO₂ adsorption energy but does not change the preferred nanorod position on zirconia. Altogether, our results highlight that CO₂ adsorption and activation depend sensitively on the chemical composition and atomic structure of the interface used in the calculations. This structure sensitivity may potentially impact further catalytic steps and the overall computed reactivity profile.

Tuning CuZn interfaces in metal–organic framework-derived electrocatalysts for enhancement of CO2 conversion to C2 products

CuZn alloy derived from a metal–organic framework shows a 5-fold enhancement in faradaic efficiency for CO2 reduction to C2 products compared to Cu alone. Density functional theory calculation provides important mechanistic insights.

Approaching full-range selectivity control in CO2 hydrogenation to methanol and carbon monoxide with catalyst composition regulation

P-Modified In₂O₃ with composition regulation for approaching full-range selectivity control in CO₂ hydrogenation to methanol and carbon monoxide.

Engineering Heterostructured Nanocatalysts for CO2 Transformation Reactions: Advances and Perspectives

As a conceivable route to achieving anthropological carbon looping, carbon capture and utilization (CCU) technologies employ waste CO₂ as an accessible C1 building block to generate upgraded chemicals or fuels, thereby simultaneously remedying environmental issues and energy crises. However, efficient CO₂ conversion is disfavored by both its thermodynamics and its kinetics. Heterostructured materials with well-controlled interfaces have great potential for enhanced catalytic performance in various CO₂ transformation reactions, owing to the synergistic effects among components, numerous interfacial and/or surface active sites, increased CO₂ adsorption capacity, promoted charge transfer efficiency, and unique physicochemical properties. This Review highlights the state of the art in typical heterostructures, such as core-shell, yolk-shell, Janus, hierarchical (branched and hollow), and 2D/2D layered structures, applied for CO₂ conversion with various energy inputs (radiation, electricity, heat). Fabrication methods of different heterostructures and structure-composition-performance relationships are also discussed concisely. Finally, a brief summary and prospective research directions are provided. The motivation of this Review is to offer instructive information on the applicability of inorganic heterostructures for CO₂ transformation reactions, and it is hoped that further enlightening studies in this field could emerge in the future.

Electrocatalysts for direct methanol fuel cells to demonstrate China's renewable energy renewable portfolio standards within the framework of the 13th five-year plan

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Methanol synthesis via carbon dioxide hydrogenation is reviewed.

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Up to date review on high yield catalysts for methanol synthesis are discussed.

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Catalytic performance parameters (temperature, Pressure, Support) are reviewed.

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Policy framework towards renewable energy for China is extensively reviewed.

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The catalytic mechanism and the role of promoters, bi-metallic catalyst is also discussed.

A unified treatment of the renewable portfolio standards is given concerning direct methanol fuel. The current mechanism of electrocatalysis of methanol oxidation on platinum and non-platinum-containing alloys is summarized for the systematic improvement of the rate of electro-oxidation of methanol are discussed. Policy realignment under the five-year plan is discussed in length to demonstrate how policy, markets, and engineering designs contribute towards the development of model direct methanol fuel cells operational enhancement, and factors that affect critical performance parameters for commercial exploitation are summarized for catalytic formulations and cell design within the context of why this investment in technology, education, and finances is required within the global context of sustainable energy and energy independence as exposed by thirteenth the five-year plan. The prolog focuses on the way, whereas the section on methanol fuel cells on the how and the post log on what is expected post-COVID-19 era in science and technology as China pivots to a post-fossil fuel economy.

China's industrial growth has been through internal market reforms and supplies side economics from the Chinese markets for fossil fuels except for petroleum. The latest renewable portfolio standards adopted have common elements as adopted from North American and the United Kingdom in terms of adaptation of obligation in terms of renewable portfolio standards as well as a realization that the necessity for renewables standards for the thirteen five year plan (from 2016 to 2020) need to less rigorously implemented due to performance targets that were met during the eleventh (06–10) and twelfth five-year plans (11–15) in terms of utilization of small coal-ire power plants, development of newer standards, led to an improvement of energy efficiency of 15 %, reduction of SO_x/NO_x by an average of 90 % and PM2.5 by 96 % over the last two five-year plans.

The current phase of the plan has a focus on energy generation from coal and a slowing down of renewables or Renewable energy curtailment of approximately 400 T Wh renewables including 300 T Wh of non-hydro power, principally from Guangdong, and Jiangsu for transfer of hydropower and Zhejiang, Tianjin, Henan for non-hydro power transfer with Beijing and Shanghai playing important roles in renewables energy curtailment and realignment using an integrated approach to optimize each provinces energy portfolio. The realignment of the renewable energy portfolio indicates that the newly installed capacity in Sichuan, Yunnan, Inner Mongolia, and Zhejiang will account for less than 20 % of the current renewable energy portfolio but with the NO_x SO_x and PM_2.5 savings already accrued.

The catalytic reduction of carbon dioxide to methanol (70 / 110 million metric tons from all sources in 2019 for China/world) is one technological approach to reduce global carbon dioxide emissions and suggests that catalytic methanol synthesis by CO₂ hydrogenation may be a plausible approach, even if it is more expensive economically than methanol synthesis by the syngas approach. This is because the CO₂ emissions of the synthesis are lower than other synthesis methodologies. The Chinese government has placed a premium on cleaner air and water and may view such an approach as solving the dual issues of fuel substitution and reduction of CO₂. Thus, the coupling of hydrogen generation from sustainable energies sources (Solar 175 / 509 GW) or wind (211/591.5 GW in 2019) may be an attractive approach, as this requires slightly less water than coal gasification. Due to the thermodynamic requirement of lower operating pressure and higher operating pressure, currently, there is no single operational approach, although some practice approaches (220 °C at 48 atm using copper) and zinc oxide/alumina are suggested for optimal performance.

The Study of Reverse Water Gas Shift Reaction Activity over Different Interfaces: The Design of Cu-Plate ZnO Model Catalysts

CO2 hydrogenation to methanol is one of the main and valuable catalytic reactions applied on Cu/ZnO-based catalysts; the interface formed through Zn migration from ZnO support to the surface of Cu nanoparticle (ZnOx-Cu NP-ZnO) has been reported to account for methanol synthesis from CO2 hydrogenation. However, the accompanied reverse water gas shift (RWGS) reaction significantly decreases methanol selectivity and deactivates catalysts soon. Inhibition of RWGS is thus of great importance to afford high yield of methanol. The clear understanding of the reactivity of RWGS reaction on both the direct contact Cu-ZnO interface and ZnOx-Cu NP-ZnO interface is essential to reveal the low methanol selectivity in CO2 hydrogenation to methanol and look for efficient catalysts for RWGS reaction. Cu doped plate ZnO (ZnO:XCu) model catalysts were prepared through a hydrothermal method to simulate direct contact Cu-ZnO interface and plate ZnO supported 1 wt % Cu (1Cu/ZnO) catalyst was prepared by wet impregnation for comparison in RWGS reaction. Electron paramagnetic resonance (EPR), XRD, SEM, Raman, hydrogen temperature-programmed reduction (H2-TPR) and CO2 temperature-programmed desorption (CO2-TPD) were employed to characterize these catalysts. The characterization results confirmed that Cu incorporated into ZnO lattice and finally formed direct contact Cu-ZnO interface after H2 reduction. The catalytic performance revealed that direct contact Cu-ZnO interface displays inferior RWGS reaction reactivity at reaction temperature lower than 500 °C, compared with the ZnOx-Cu NP-ZnO interface; however, it is more stable at reaction temperature higher than 500 °C, enables ZnO:XCu model catalysts superior catalytic activity to that of 1Cu/ZnO. This finding will facilitate the designing of robust and efficient catalysts for both CO2 hydrogenation to methanol and RWGS reactions.

Ultrasmall Ni-ZnO/SiO2 Synergistic Catalyst for Highly Efficient Hydrogenation of NaHCO3 to Formic Acid

Conversion of CO₂ into fuels and chemicals has been considered to be an important strategy to reduce greenhouse gas emissions and alleviate the energy crisis. Bicarbonate as a CO₂ source is convenient for experimental operation. Herein, based on the synergistic effect of Ni and ZnO benefitting from the electronic transfer, ultrasmall Ni-ZnO clusters (∼2 nm) stabilized by microporous silica nanoparticles were designed and prepared for catalyzing the hydrogenation of sodium bicarbonate to formic acid. The yield of formic acid reached up to 97.0% at 260 °C/3 MPa for 2 h, which is higher than those reported non-noble metal-based catalysts. The good performance of Ni-ZnO/SiO₂ can be attributed to the ultrasmall active component size and the synergy effect based on electron transfer between Ni and ZnO.

Enhanced CH3OH selectivity in CO2 hydrogenation using Cu-based catalysts generated via SOMC from GaIII single-sites

Small and narrowly distributed nanoparticles of copper alloyed with gallium supported on silica containing residual Ga^III sites can be obtained via surface organometallic chemistry in a two-step process: (i) formation of isolated Ga^III surface sites on SiO₂ and (ii) subsequent grafting of a Cu^I precursor, [Cu(O ^t Bu)]₄, followed by a treatment under H₂ to generate CuGa _x alloys. This material is highly active and selective for CO₂ hydrogenation to CH₃OH. In situ X-ray absorption spectroscopy shows that gallium is oxidized under reaction conditions while copper remains as Cu⁰. This CuGa material only stabilizes methoxy surface species while no formate is detected according to ex situ infrared and solid-state nuclear magnetic resonance spectroscopy.

Self-tuned properties of CuZnO catalysts for hydroxymethylfurfural hydrodeoxygenation towards dimethylfuran production

CuZnO is used as robust, efficient and self-tuned catalyst for the conversion of 5-hydroxymethylfurfural (5-HMF) into 2,5-dimethylfuran (DMF) or 2,5-bishydroxymethylfuran (BHMF) depending on the preparation method and the reaction environment.

Transformation of γ-valerolactone into 1,4-pentanediol and 2-methyltetrahydrofuran over Zn-promoted Cu/Al2O3 catalysts

The presence of Zn can promote the activity and stability as well as adjust the product selectivity due to the formation of ZnCu alloy and the reduction of acidic sites, which prevents the deactivation of the catalyst and dehydration of 1,4-PDO.