Alkali ions secure hydrides for catalytic hydrogenation

Tuning the Electronic Structures of Anchor Sites to Achieve Zero-Valence Single-Atom Catalysts for Advanced Hydrogenation

Single-atom catalysts (SACs) have recently become highly attractive for selective hydrogenation reactions owing to their remarkably high selectivity. However, compared to their nanoparticle counterparts, atomically dispersed metal atoms in SACs often show inferior activity and are prone to aggregate under reaction conditions. Here, by theoretical calculations, we show that tuning the local electronic structures of metal anchor sites on g-C3N4 by doping B atoms (BCN) with relatively lower electronegativity allows achieving zero-valence Pd SACs with reinforced metal-support orbital hybridizations for high stability and upshifted Pd 4d orbitals for high activity in H2 activation. The precise synthesis of Pd SACs on BCN supports with varied B contents substantiated the theoretical prediction. A zero-valence Pd1/BCN SAC was achieved on a BCN support with a relatively low B content. It exhibited much higher stability in a H2 reducing environment, and more strikingly, a hydrogenation activity, approximately 10 and 34 times greater than those high-valence Pd1/g-C3N4 and Pd1/BCN with a high B content, respectively.

Promoted hydrogenation of CO2 to methanol over single-atom Cu sites with Na+-decorated microenvironment

Although single-atom Cu sites exhibit high efficiency in CO2 hydrogenation to methanol, they are prone to forming Cu nanoparticles due to reduction and aggregation under reaction conditions, especially at high temperatures. Herein, single-atom Cu sites stabilized by adjacent Na+ ions have been successfully constructed within a metal-organic framework (MOF)-based catalyst, namely MOF-808-NaCu. It is found that the electrostatic interaction between the Na+ and Hδ- species plays a pivotal role in upholding the atomic dispersion of Cu in MOF-808-NaCu during CO2 hydrogenation, even at temperatures of up to 275°C. This exceptional stabilization effect endows the catalyst with excellent activity (306 g·kgcat-1·h-1), high selectivity to methanol (93%) and long-term stability at elevated reaction temperatures, far surpassing the counterpart in the absence of Na+ (denoted as MOF-808-Cu). This work develops an effective strategy for the fabrication of stable single-atom sites for advanced catalysis by creating an alkali-decorated microenvironment in close proximity.

Structural Design of Single-Atom Catalysts for Enhancing Petrochemical Catalytic Reaction Process

Petroleum, as the "lifeblood" of industrial development, is the important energy source and raw material. The selective transformation of petroleum into high-end chemicals is of great significance, but still exists enormous challenges. Single-atom catalysts (SACs) with 100% atom utilization and homogeneous active sites, promise a broad application in petrochemical processes. Herein, the research systematically summarizes the recent research progress of SACs in petrochemical catalytic reaction, proposes the role of structural design of SACs in enhancing catalytic performance, elucidates the catalytic reaction mechanisms of SACs in the conversion of petrochemical processes, and reveals the high activity origins of SACs at the atomic scale. Finally, the key challenges are summarized and an outlook on the design, identification of active sites, and the appropriate application of artificial intelligence technology is provided for achieving scale-up application of SACs in petrochemical process.

Element-dependent effects of alkali cations on nitrate reduction to ammonia

Catalytic conversion of nitrate (NO3-) pollutants into ammonia (NH3) offers a sustainable and promising route for both wastewater treatment and NH3 synthesis. Alkali cations are prevalent in nitrate solutions, but their roles beyond charge balance in catalytic NO3- conversion have been generally ignored. Herein, we report the promotion effect of K+ cations in KNO3 solution for NO3- reduction over a TiO2-supported Ni single-atom catalyst (Ni1/TiO2). For photocatalytic NO3- reduction reaction, Ni1/TiO2 exhibited a 1.9-fold NH3 yield rate with nearly 100% selectivity in KNO3 solution relative to that in NaNO3 solution. Mechanistic studies reveal that the K+ cations from KNO3 gradually bonded with the surface of Ni1/TiO2, in situ forming a K-O-Ni moiety during reaction, whereas the Na+ ions were unable to interact with the catalyst in NaNO3 solution. The charge accumulation on the Ni sites induced by the incorporation of K atom promoted the adsorption and activation of NO3-. Furthermore, the K-O-Ni moiety facilitated the multiple proton-electron coupling of NO3- into NH3 by stabilizing the intermediates.

Frustrated Lewis pairs on pentacoordinated Al3+-enriched Al2O3 promote heterolytic hydrogen activation and hydrogenation

As an emerging class of metal-free catalysts, frustrated Lewis pairs (FLPs) catalysts have been greatly constructed and applied in many fields. Homogeneous FLPs have witnessed significant development, while limited heterogeneous FLPs catalysts are available. Herein, we report that heterogeneous FLPs on pentacoordinated Al3+-enriched Al2O3 readily promote the heterolytic activation of H2 and thus hydrogenation catalysis. The defect-rich Al2O3 was prepared by simple calcination of a carboxylate-containing Al precursor. Combinatorial studies confirmed the presence of rich FLPs on the surface of the defective Al2O3. In contrast to conventional alumina (γ-Al2O3), the FLP-containing Al2O3 can activate H2 in the absence of any transition metal species. More importantly, H2 was activated by surface FLPs in a heterolytic pathway, leading to the hydrogenation of styrene in a stepwise process. This work paves the way for the exploration of more underlying heterogeneous FLPs catalysts and further understanding of accurate active sites and catalytic mechanisms of heterogeneous FLPs at the molecular level.

Potassium regulating electronic state of zirconia supported palladium catalyst and hydrogen spillover for improved acetylene hydrogenation

High-selectivity acetylene hydrogenation to produce ethylene is an important issue of removing acetylene impurity in ethylene for industrial polyethylene production. Developing high-efficiency catalyst with excellent ethylene selectivity and catalytic durability is desirable but still challenging. In this work, potassium doped palladium catalysts supported on zirconia with different K contents (Pd/ZrO2-xK) have been developed to catalyze acetylene hydrogenation, the Pd/ZrO2-16K exhibits impressive catalytic performance with acetylene conversion of 100 %, ethylene selectivity of 81 % and high catalytic durability. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), in situ synchrotron radiation photoionization mass spectrometry (SR-PIMS) and density functional theory (DFT) calculations reveal that K doping effectively weakens the adsorption of ethylene by regulating the electronic state of catalyst to improve ethylene selectivity and substantially lowers the barriers of hydrogen activation and transfer reactions to favor hydrogen spillover, thus conferring a remarkably improved durability on the Pd/ZrO2-16K catalysts.

Conductive catalysis by subsurface transition metals

The nature of catalysis has been hotly pursued for over a century, and current research is focused on understanding active centers and their electronic structures. Herein, the concept of conductive catalysis is proposed and verified by theoretical simulations and experimental observations. Metallic systems containing buried catalytically active transitional metals and exposed catalytically inert main group metals are constructed, and the electronic interaction between them via metallic bonding is disclosed. Through the electronic interaction, the catalytic properties of subsurface transitional metals (Pd or Rh) can be transferred to outermost main group metals (Al or Mg) for several important transformations like semi-hydrogenation, Suzuki-coupling and hydroformylation. The catalytic force is conductive, in analogy with the magnetic force and electrostatic force. The traditional definition of active centers is challenged by the concept of conductive catalysis and the electronic nature of catalysis is more easily understood. It might provide new opportunities for shielding traditional active centers against poisoning or leaching and allow for precise regulation of their catalytic properties by the conductive layer.

First-principles study of CO2 hydrogenation on Cd-doped ZrO2: Insights into the heterolytic dissociation of H2

Cd-doped ZrO2 catalyst has been found to have high selectivity and activity for CO2 hydrogenation to methanol. In this work, density functional theory calculations were carried out to investigate the microscopic mechanism of the reaction. The results show that Cd doping effectively promotes the generation of oxygen vacancies, which significantly activate the CO2 with stable adsorption configurations. Compared with CO2, gaseous H2 adsorption is more difficult, and it is mainly dissociated and adsorbed on the surface as [HCd-HO]* or [HZr-HO]* compact ion pairs, with [HCd-HO]* having the lower energy barrier. The reaction pathways of CO2 to methanol has been investigated, revealing the formate path as the dominated pathway via HCOO* to H2COO* and to H3CO*. The hydrogen anions, HCd* and HZr*, significantly reduce the energy barriers of the reaction.

Investigation of Ni-Cu-acid multifunctional synergism in NiCu-phyllosilicate catalysts toward the 1,4-butynediol hydrogenation to 1,4-butanediol

We studied the Ni-Cu-acid multifunctional synergism in NiCu-phyllosilicate catalysts toward 1,4-butynediol hydrogenation to 1,4-butanediol by varying the reduction temperature, which can activate different bimetal and support interactions. Compared with a monometallic Ni phyllosilicate (phy), which only showed one type of metal species when reduced at ∼750 °C, there are three types of metal species for the bimetallic Ni-Cu-phyllosilicate derived catalysts, namely Cuphy, differentiated Ni, and Niphy. Thorough structure-activity/selectivity correlation investigations showed that, although the Ni9Cu1-P catalyst matrix can produce tiny amounts of differentiated Ni0 species under the induction of reduced Cu0 at R250 condition, it could not form Ni-Cu bimetallic interactions for the collaborative hydrogenation of 1,4-butynediol, and the product stays in the semi hydrogenated state. When the reduction temperature is raised to 500 °C, stable Ni-Cu alloy active sites exist, accompanied by the strong metal support interaction and metal acid effect derived from the intimate contact between the extracted metal sites and the surviving functional phyllosilicate support; these functionalities yield a supreme hydrogenation performance of the R500 sample with a 1,4-butanediol yield larger than 91.2%.

Highly Enhancing CO2 Photoreduction by Metallization of an Imidazole-linked Robust Covalent Organic Framework

Converting CO2 into value-added chemicals to solve the issues caused by carbon emission is promising but challenging. Herein, by embedding metal ions (Co2+ , Ni2+ , Cu2+ , and Zn2+ ) into an imidazole-linked robust photosensitive covalent organic framework (PyPor-COF), effective photocatalysts for CO2 conversion are rationally designed and constructed. Characterizations display that all of the metallized PyPor-COFs (M-PyPor-COFs) display remarkably high enhancement in their photochemical properties. Photocatalysis reactions reveal that the Co-metallized PyPor-COF (Co-PyPor-COF) achieves a CO production rate as high as up to 9645 µmol g-1 h-1 with a selectivity of 96.7% under light irradiation, which is more than 45 times higher than that of the metal-free PyPor-COF, while Ni-metallized PyPor-COF (Ni-PyPor-COF) can further tandem catalyze the generated CO to CH4 with a production rate of 463.2 µmol g-1 h-1 . Experimental analyses and theory calculations reveal that their remarkable performance enhancement on CO2 photoreduction should be attributed to the incorporated metal sites in the COF skeleton, which promotes the adsorption and activation of CO2 and the desorption of generated CO and even reduces the reaction energy barrier for the formation of different intermediates. This work demonstrates that by metallizing photoactive COFs, effective photocatalysts for CO2 conversion can be achieved.

New Function of Metal-Organic Framework: Structurally Ordered Metal Promoter

The remarkable roles of metal promoters have been known for nearly a century, but it is still a challenge to find a suitable structure model to reveal the action mechanism behind metal promoters. Herein, a new function of metal-organic frameworks (MOFs) is developed as an ideal model to construct structurally ordered metal promoters by a targeted post-modification strategy. MOFs as model not only favor clearing the real action mechanism behind metal promoters, but also can anchor one or multiple kinds of metal promoters especially noble metal promoters. Typically, the as-prepared Pd/bpy-UiO-Cu catalysts show high selectivity (>99%) toward 4-nitrophenylethane in 4-nitrostyrene hydrogenation, mainly due to the enhanced interaction between Pd nanoparticles and MOF carriers induced by Cu promoters, thus inhibiting the hydrogenation of 4-nitrophenylethane. This strategy with flexibility and universality will open up a new route to synthesize efficient catalysts with structurally ordered metal promoters.

Regulating the Pt1-CeO2 interaction via alkali modification for boosting the catalytic performance of single-atom catalysts

With the introduction of potassium species, the catalytic oxidation performance over the Pt₁/CeO₂ catalyst was significantly enhanced, where potassium ions acted as structural and electronic promoters, and formed Pt-O-K interactions with Pt to directly regulate the coordination environment and electronic state of Pt and the metal-support interaction between Pt and CeO₂.

The stochastic wave function method for diffusion of alkali atoms on metallic surfaces

The stochastic wave function method is proposed to study the diffusion regimes of alkali atoms on metallic surfaces. The Lindblad approach, based on the microscopic Hamiltonian information in the Caldeira-Leggett model, is presented and numerical calculations of the dynamics are carried out to characterize surface diffusion for two different systems: Na-Cu(111) and Li-Cu(111). Calculations of the intermediate scattering function for an isolated adsorbate are compared, in the Brownian limit, with results deduced from helium spin-echo (HeSE) experiments after reducing them to single adsorbate dynamics. To illustrate the method we present the dependence on momentum transfer and the temperature dependency. Results show that the experiment can be described at a quantitative level by the 1-D quantum model (reduced dimensionality).

Tuning the CO2 Hydrogenation Selectivity of Rhodium Single-Atom Catalysts on Zirconium Dioxide with Alkali Ions

Tuning the coordination environments of metal single atoms (M₁ ) in single-atom catalysts has shown large impacts on catalytic activity and stability but often barely on selectivity in thermocatalysis. Here, we report that simultaneously regulating both Rh₁ atoms and ZrO₂ support with alkali ions (e.g., Na) enables efficient switching of the reaction products from nearly 100 % CH₄ to above 99 % CO in CO₂ hydrogenation in a wide temperature range (240-440 °C) along with a record high activity of 9.4 mol_CO  g_Rh ^-1  h^-1 at 300 °C and long-term stability. In situ spectroscopic characterization and theoretical calculations unveil that alkali ions on ZrO₂ change the surface intermediate from formate to carboxy species during CO₂ activation, thus leading to exclusive CO formation. Meanwhile, alkali ions also reinforce the electronic Rh₁ -support interactions, endowing the Rh₁ atoms more electron deficient, which improves the stability against sintering and inhibits deep hydrogenation of CO to CH₄ .

Co-Dissolved Isostructural Polyoxovanadates to Construct Single-Atom-Site Catalysts for Efficient CO2 Photoreduction

We explored a co-dissolved strategy to embed mono-dispersed Pt center into V₂ O₅ support via dissolving [PtV₉ O₂₈ ]^7- into [V₁₀ O₂₈ ]^6- aqueous solution. The uniform dispersion of [PtV₉ O₂₈ ]^7- in [V₁₀ O₂₈ ]^6- solution allows [PtV₉ O₂₈ ]^7- to be surrounded by [V₁₀ O₂₈ ]^6- clusters via a freeze-drying process. The V centers in both [PtV₉ O₂₈ ]^7- and [V₁₀ O₂₈ ]^6- were converted into V₂ O₅ via a calcination process to stabilize Pt center. These double separations can effectively prevent the Pt center agglomeration during the high-temperature conversion process, and achieve 100 % utilization of Pt in [PtV₉ O₂₈ ]^7- . The resulting Pt-V₂ O₅ single-atom-site catalysts exhibit a CH₄ yield of 247.6 μmol g^-1  h^-1 , 25 times higher than that of Pt nanoparticle on the V₂ O₅ support, which was accompanied by the lactic acid photooxidation to form pyruvic acid. Systematical investigations on this unambiguous structure demonstrate an important role of Pt-O atomic pair synergy for highly efficient CO₂ photoreduction.

Surface Spin Enhanced High Stable NiCo2 S4 for Energy-Saving Production of H2 from Water/Methanol Coelectrolysis at High Current Density

Nickel based materials are promising electrocatalysts to produce hydrogen from water in alkaline media. However, the stability is of great challenge, limiting its practical material functions. Herein, a new technique for electro-deposition flower-like NiCo₂ S₄ nanosheets on carbon-cloth (CC@NiCo₂ S₄ ) is proposed for energy-saving production of H₂ from water/methanol coelectrolysis at high current density by constructing array architectures and regulating surface magnetism. The optimized and fine-tuned magnetism on the surface of the electrochemical in situ grown CC@NiCo₂ S₄ nanosheet array result in (0 1 -1) surface universally exposed, high catalytic activity for methanol electrooxidation, and long-term stability at high current density. X-ray photoelectron spectroscopy in combination of density functional theory calculations confirm the valence electron states and spin of d electrons for the surface of NiCo₂ S₄ , which enhance the surface stability of catalysts. This technology may be utilized to alter the surface magnetism and increase the stability of Ni-based electrocatalytic materials in general.

Potassium Titanate Supported Atomically Dispersed Palladium for Catalytic Oxidation

Single-atom catalysts based on noble metals provide efficient atomic utilization along with enhanced reactivity. Herein, a convenient strategy to construct atomically dispersed palladium catalyst on layered potassium titanate (KTO), which has enhanced interaction between the TiO₆ layer and the palladium atoms, is presented. Due to the presence of K⁺ ions in the interlayers of KTO, the TiO₆ octahedron layers have negative charge, which increases the interaction between Pd atoms and the substrate, thus preventing their agglomeration. In addition, the provision of charge of K⁺ ion makes the molecular oxygen in the system easier to be activated and promotes catalytic oxidation activity.

Surface and Interface Coordination Chemistry Learned from Model Heterogeneous Metal Nanocatalysts: From Atomically Dispersed Catalysts to Atomically Precise Clusters

The surface and interface coordination structures of heterogeneous metal catalysts are crucial to their catalytic performance. However, the complicated surface and interface structures of heterogeneous catalysts make it challenging to identify the molecular-level structure of their active sites and thus precisely control their performance. To address this challenge, atomically dispersed metal catalysts (ADMCs) and ligand-protected atomically precise metal clusters (APMCs) have been emerging as two important classes of model heterogeneous catalysts in recent years, helping to build bridge between homogeneous and heterogeneous catalysis. This review illustrates how the surface and interface coordination chemistry of these two types of model catalysts determines the catalytic performance from multiple dimensions. The section of ADMCs starts with the local coordination structure of metal sites at the metal-support interface, and then focuses on the effects of coordinating atoms, including their basicity and hardness/softness. Studies are also summarized to discuss the cooperativity achieved by dual metal sites and remote effects. In the section of APMCs, the roles of surface ligands and supports in determining the catalytic activity, selectivity, and stability of APMCs are illustrated. Finally, some personal perspectives on the further development of surface coordination and interface chemistry for model heterogeneous metal catalysts are presented.

The Progress and Outlook of Metal Single-Atom-Site Catalysis

Single-atom-site catalysts (SASCs) featuring maximized atom utilization and isolated active sites have progressed tremendously in recent years as a highly prosperous branch of catalysis research. Varieties of SASCs have been developed that show excellent performance in many catalytic applications. The major goal of SASC research is to establish feasible synthetic strategies for the preparation of high-performance catalysts, to achieve an in-depth understanding of the active-site structures and catalytic mechanisms, and to develop practical catalysts with industrial value. This Perspective describes the up-to-date development of SASCs and related catalysts, such as dual-atom-site catalysts (DASCs) and nano-single-atom-site catalysts (NSASCs), analyzes the current challenges encountered by these catalysts for industrial applications, and proposes their possible future development path.

In Situ Chalcogen Leaching Manipulates Reactant Interface toward Efficient Amine Electrooxidation

Engineering the reaction interface is necessary for advancing various electrocatalytic processes. However, most designed catalysts tend to be ineffective due to the inevitable structural reconstruction. Here we utilize that operando electrocatalysis variations (i.e., chalcogen leaching) manipulate the reactant interface toward amine electrooxidation. Taking chalcogen-doped Ni(OH)₂ as an example, operando techniques uncover that chalcogens leach from the matrix and then adsorb on the surface of NiOOH as chalcogenates during the electrooxidation process. The charged chalcogenates will induce the local electric field that pushes the polar amines through the inner Helmholtz plane to enrich on the catalyst surface. Meanwhile, the polarization effect of chalcogenates and amines boost amino C-N bond activation for dehydrogenation into nitrile C≡N bonds. Under the promotion effect of surface-adsorbed chalcogenate ions, our catalysts display over 99.5% propionitrile selectivity at the low potential of 1.317 V with an ultrahigh current density. This finding highlights the use of operando changes of catalysts to rationally design efficient catalysts and further clarifies the underlying role of chalcogen atoms in the electrooxidation process.

Elucidating the Roles of Amorphous Alumina Overcoat in Palladium-Catalyzed Selective Hydrogenation

Amorphous alumina overcoats generated by atomic layer deposition (ALD) have been shown to improve the selectivity and durability of supported metal catalysts in many reactions. Several mechanisms have been proposed to explain the enhanced catalytic performance, but the accessibilities of reactants through the amorphous overcoats remain elusive, which is crucial for understanding reaction mechanisms. Here, we show that an AlOx ALD overcoat is able to improve the alkene product selectivity of a supported Pd catalyst in acetylene (C2H2) hydrogenation. We further demonstrate that the AlOx ALD overcoat blocks the access of C2H2 (kinetic diameter of 0.33 nm), O2 (0.35 nm), and CO (0.38 nm) but allows H2 (0.29 nm) to access Pd surfaces. A H-D exchange experiment suggests that H2 might dissociate heterolytically at the Pd-AlOx interface. These findings are in favor of a hydrogen spillover mechanism.

Programmable heating and quenching for efficient thermochemical synthesis

Conventional thermochemical syntheses by continuous heating under near-equilibrium conditions face critical challenges in improving the synthesis rate, selectivity, catalyst stability and energy efficiency, owing to the lack of temporal control over the reaction temperature and time, and thus the reaction pathways^1-3. As an alternative, we present a non-equilibrium, continuous synthesis technique that uses pulsed heating and quenching (for example, 0.02 s on, 1.08 s off) using a programmable electric current to rapidly switch the reaction between high (for example, up to 2,400 K) and low temperatures. The rapid quenching ensures high selectivity and good catalyst stability, as well as lowers the average temperature to reduce the energy cost. Using CH₄ pyrolysis as a model reaction, our programmable heating and quenching technique leads to high selectivity to value-added C₂ products (>75% versus <35% by the conventional non-catalytic method and versus <60% by most conventional methods using optimized catalysts). Our technique can be extended to a range of thermochemical reactions, such as NH₃ synthesis, for which we achieve a stable and high synthesis rate of about 6,000 μmol g_Fe^-1 h^-1 at ambient pressure for >100 h using a non-optimized catalyst. This study establishes a new model towards highly efficient non-equilibrium thermochemical synthesis.

Atomically Dispersed Zn-Stabilized Niδ+ Enabling Tunable Selectivity for CO2 Hydrogenation

For a heterogeneous catalytic process, the performance of catalysts could be improved by modifying the active metal with a second element. Determining the enhanced mechanism of the second element is essential to the rational design of catalysts. In this work, Zn was introduced as a second element into Ni/ZrO₂ for CO₂ hydrogenation. In contrast to Ni/ZrO₂ , the selectivity of NiZn/ZrO₂ is observed to shift from CH₄ to CO. A series of structural characterization results reveals that Zn is atomically dispersed in the NiO and ZrO₂ phases as NiZnO_x and ZnZrO_x , respectively during CO₂ hydrogenation, stabilizing a higher valence state of Ni (Ni^δ+ ) under a hydrogenation atmosphere over Ni-O-Zn site and thus promoting the generation of CO. These findings shed light on the O-mediated bimetallic effect of NiZn/ZrO₂ and bring new insight into the rational design of more efficient heterogeneous catalysts.

The promotion effect of π-π interactions in Pd NPs catalysed selective hydrogenation

The utilization of weak interactions to improve the catalytic performance of supported metal catalysts is an important strategy for catalysts design, but still remains a big challenge. In this work, the weak interactions nearby the Pd nanoparticles (NPs) are finely tuned by using a series of imine-linked covalent organic frameworks (COFs) with different conjugation skeletons. The Pd NPs embedded in pyrene-COF are ca. 3 to 10-fold more active than those in COFs without pyrene in the hydrogenation of aromatic ketones/aldehydes, quinolines and nitrobenzene, though Pd have similar size and surface structure. With acetophenone (AP) hydrogenation as a model reaction, systematic studies imply that the π-π interaction of AP and pyrene rings in the vicinity of Pd NPs could significantly reduce the activation barrier in the rate-determining step. This work highlights the important role of non-covalent interactions beyond the active sites in modulating the catalytic performance of supported metal NPs.

Unprecedentedly high activity and selectivity for hydrogenation of nitroarenes with single atomic Co1-N3P1 sites

Transition metal single atom catalysts (SACs) with M1-Nx coordination configuration have shown outstanding activity and selectivity for hydrogenation of nitroarenes. Modulating the atomic coordination structure has emerged as a promising strategy to further improve the catalytic performance. Herein, we report an atomic Co1/NPC catalyst with unsymmetrical single Co1-N3P1 sites that displays unprecedentedly high activity and chemoselectivity for hydrogenation of functionalized nitroarenes. Compared to the most popular Co1-N4 coordination, the electron density of Co atom in Co1-N3P1 is increased, which is more favorable for H2 dissociation as verified by kinetic isotope effect and density functional theory calculation results. In nitrobenzene hydrogenation reaction, the as-synthesized Co1-N3P1 SAC exhibits a turnover frequency of 6560 h-1, which is 60-fold higher than that of Co1-N4 SAC and one order of magnitude higher than the state-of-the-art M1-Nx-C SACs in literatures. Furthermore, Co1-N3P1 SAC shows superior selectivity (>99%) toward many substituted nitroarenes with co-existence of other sensitive reducible groups. This work is an excellent example of relationship between catalytic performance and the coordination environment of SACs, and offers a potential practical catalyst for aromatic amine synthesis by hydrogenation of nitroarenes.

Single Atom Sites Catalysts based on High Specific Surface Area Supports

Catalysis is the heart of modern chemical industry. Supports with high specific surface area are crucial for the fabrication of efficient catalysts with elevated metal dispersion. Single atom sites catalysts...

Kilo-scale synthesis and purification of 4,4′-[di-t-butyldibenzo]-18-crown-6 and its catalytic reduction to 4,4′-[di-t-butyldicyclohexano]-18-crown-6

This article reports the large scale synthesis, scale up chromatographic purification and Rh catalyzed hydrogenation of DTBDB18C6. Confirmation of molecular structure was done by SCXRD and complete hydrogenation was achieved with the use of K+ ions.

The mechanism of alkali promoting water splitting on g-C3N4

Alkali promotes H+ to obtain electrons and turn into H2.

Towards the development of the emerging process of CO2 heterogenous hydrogenation into high-value unsaturated heavy hydrocarbons

The emerging process of CO₂ hydrogenation through heterogenous catalysis into important bulk chemicals provides an alternative strategy for sustainable and low-cost production of valuable chemicals, and brings an important chance for mitigating CO₂ emissions. Direct synthesis of the family of unsaturated heavy hydrocarbons such as α-olefins and aromatics via CO₂ hydrogenation is more attractive and challenging than the production of short-chain products to modern society, suffering from the difficult control between C-O activation and C-C coupling towards long-chain hydrocarbons. In the past several years, rapid progress has been achieved in the development of efficient catalysts for the process and understanding of their catalytic mechanisms. In this review, we provide a comprehensive, authoritative and critical overview of the substantial progress in the synthesis of α-olefins and aromatics from CO₂ hydrogenation via direct and indirect routes. The rational fabrication and design of catalysts, proximity effects of multi-active sites, stability and deactivation of catalysts, reaction mechanisms and reactor design are systematically discussed. Finally, current challenges and potential applications in the development of advanced catalysts, as well as opportunities of next-generation CO₂ hydrogenation techniques for carbon neutrality in future are proposed.

Embedding ruthenium nanoparticles in the shell layer of titanium zirconium oxide hollow spheres to catalyze the degradation of alkali lignin under mild condition

To catalyze the degradation of lignin in refractory wastewater efficiently, a new nanocomposite with Ru nanoparticles embedded on the surface of TiZrO₄ hollow spheres was fabricated with three method a "sol-gel + calcination + vacuum-impregnation" template method, and the unique binary composition of TiZrO₄/Ru prevented the aggregation of Ru and keep its high activity. During 3-h catalytic-oxidation at 160 °C and 2.0 MPa O₂, 98% alkali lignin was degraded and 70% organic carbon was mineralized with the catalysis of TiZrO₄/Ru, while the values were only 50% and 25% without analysts. The catalyst increased the catalytic-oxidation rate constant k₁ (h^-1) of alkali lignin from 0.282 h^-1 to 1.175 h^-1 because of high-efficiency hydroxyl radical production, as determined by EPR. LC-OCD showed that the catalyst decomposed alkali lignin with molecular weight 1-2 kDa to small molecules. Butyl acetate was the main intermediate product, which should be derived from the auto synthesis of butanol and acetic acid. In addition to high conversion efficiency, the catalyst had good stability with 95% capability after five cycles. In real biogas slurry treatment, an increase of biochemical to COD ratio from 0.28 to 0.51, with obvious decoloration, indicated TiZrO₄/Ru enhanced the biodegradability of the refractory wastewater significantly.