Heterogeneous Catalytic Materials Research Articles

Redox-induced controllable engineering of MnO2-MnxCo3-xO4 interface to boost catalytic oxidation of ethane

Multicomponent oxides are intriguing materials in heterogeneous catalysis, and the interface between various components often plays an essential role in oxidations. However, the underlying principles of how the hetero-interface affects the catalytic process remain largely unexplored. Here we report a unique structure design of MnCoOx catalysts by chemical reduction, specifically for ethane oxidation. Part of the Mn ions incorporates with Co oxides to form spinel MnxCo3-xO4, while the rests stay as MnO2 domains to create the MnO2-MnxCo3-xO4 interface. MnCoOx with Mn/Co ratio of 0.5 exhibits an excellent activity and stability up to 1000 h under humid conditions. The synergistic effects between MnO2 and MnxCo3-xO4 are elucidated, in which the C2H6 tends to be adsorbed on the interfacial Co sites and subsequently break the C-H bonds on the reactive lattice O of MnO2 layer. Findings from this study provide valuable insights for the rational design of efficient catalysts for alkane combustion.

Heterogeneous Porous Synergistic Photocatalysts for Organic Transformations.

Recent interest has surged in using heterogeneous carriers to boost synergistic photocatalysis for organic transformations. Heterogeneous catalysts not only facilitate synergistic enhancement of distinct catalytic centers compared to their homogeneous counterparts, but also allow for the easy recovery and reuse of catalysts. This mini-review summarizes recent advancements in developing heterogeneous carriers, including metal-organic frameworks, covalent-organic frameworks, porous organic polymers, and others, for synergistic catalytic reactions. The advantages of porous materials in heterogeneous catalysis originate from their ability to provide a high surface area, facilitate enhanced mass transport, offer a tunable chemical structure, ensure the stability of active species, and enable easy recovery and reuse of catalysts. Both photosensitizers and catalysts can be intricately incorporated into suitable porous carriers to create heterogeneous dual photocatalysts for organic transformations. Notably, experimental evidence from reported cases has shown that the catalytic efficacy of heterogeneous catalysts often surpasses that of their homogeneous analogues. This enhanced performance is attributed to the proximity and confinement effects provided by the porous nature of the carriers. It is expected that porous carriers will provide a versatile platform for integrating diverse catalysts, thus exhibiting superior performance across a range of organic transformations and appealing prospect for industrial applications.

Electrocatalytic Properties of Electrochemically‐Polymerized Metal‐Phenolic Networks

AbstractMetal‐phenolic networks (MPNs) are a promising platform for developing new heterogeneous catalytic materials for water splitting technologies. This study systematically investigates the relationship between MPN composition and catalytic properties via electropolymerization of copper and cobalt combined with lignin, tannic acid, epigallocatechin‐3‐gallate (EGCG), and gallic acid polyphenols. We find that the choice of metal, size of polyphenol, and polymerization method have the greatest impact on the propensity of MPNs for catalyzing hydrogen evolution. For example, gallic acid‐based MPNs result in smoother surfaces with ~2 nm roughness, resulting in low surface area and lower average current densities compared to all other polyphenols tested. Cobalt‐based MPNs show higher current densities compared to copper, yet higher onset potentials. The results provide a map of design choices that can be used to increase the catalytic performance of new materials used in water electrolysis.

Synthesis, immobilization and acid‑catalyzed application of binary and ternary deep eutectic solvent: Synthesis of diphenylamine by condensation of aniline

Binary and ternary acidic deep eutectic solvents (ADES) were synthesized by using choline chloride as hydrogen bond acceptor, trifluoromethanesulfonic acid and glycerol as hydrogen bond donors, respectively. They were immobilized on β zeolite. The structure and surface morphology were characterized by FTIR, 1H NMR, XRD and SEM, which proved the successful preparation and immobilization of ADES. The catalytic performance of the materials was investigated by the reaction of aniline condensation to prepare diphenylamine. Both ADES and immobilized ADES showed extremely high catalytic activity. Among them, immobilized ADES as a new heterogeneous catalytic material, breaks through the limitation of difficult separation of homogeneous catalysts, and has high economy, high activity and environmental protection. The hydrogen bonding interaction and catalytic mechanism between the components were further discussed in combination with the reaction mechanism.

Enhanced Catalytic Ozonation of Phenol Degradation by Mn-Loaded γ-Al2O3 Catalyst: A Facile Strategy for Treating Organic Wastewater

Heterogeneous catalysis ozonation technology can achieve efficient treatment of refractory organics in industrial wastewater due to its advantages including fast reaction speed, high ozone utilization rate, low catalyst loss and low cost and has a broad application prospect. The development of efficient and stable heterogeneous ozone catalytic materials is the key to promoting the application of this technology in industrial wastewater treatment. Based on this, an Mn/Al2O3 catalyst was successfully prepared by impregnation method using 3~5 mm γ-Al2O3 pellets as the carrier, and the surface morphology characteristics, elemental state and phase composition of the catalyst were investigated by SEM-EDX, XRD and XPS. The results showed that Mn was successfully loaded onto the surface of a γ-Al2O3 carrier. On this basis, intermittent single factor experiments were conducted to systematically investigate the effects of catalyst dosage, pH, and ozone concentration on the catalytic performance of phenol. It was found that under the optimal conditions of a catalyst dosage of 100 g (filling height of 14.2 cm), pH of 7, and ozone concentration of 4 mg/L (gas volume of 1 L/min), the removal efficiencies of 800 mL 100 mg/L of simulated phenol wastewater reached 100% after 60 min of reaction. The removal efficiencies of the catalyst still reached 95.8% within 60 min even after the fifth cycle reaction, indicating excellent reusability of the catalyst. This work provides a facile strategy for the treatment of refractory organics in industrial wastewater.

CuCo2O4@ACoNi-LDH (A=Fe, Cu, Zn, Cr) as efficient electrocatalyst for freshwater, seawater and urea oxidation reaction

Water electrolysis has a promising prospect in the production of green hydrogen energy, but its oxygen evolution reaction kinetics is relatively slow. Therefore, in this experiment, CuCo2O4@ACoNi-LDH (A = Fe, Cu, Zn, Cr) with heterogeneous core-shell catalytic material was firstly prepared by means of hydrothermal and calcination process, and its anodic oxidation reaction in freshwater, seawater and urea was investigated. In the oxygen evolution reaction (OER) of electrolytic water, CuCo2O4@CuCoNi-LDH displays the best catalytic activity. When the current density is 10 mA cm−2, only the overpotential of 199 mV is needed (potential of 1.429 V). The competitive oxidation and corrosion of chloride ions in seawater result in the decrease of catalytic activity. For urea oxidation reaction (UOR), CuCo2O4@FeCoNi-LDH displays the best catalytic performance, only potential of 1.292 V was required with the same current density, and the catalyst had good stability during the reaction for 12 h. Density functional theory calculation shows that CuCo2O4 plays an important role in the catalytic process. The synergistic catalysis of FeCoNi-LDH and CuCo2O4 results in the improvement of catalyst activity and stability. The CuCo2O4 material plays a key role in catalyzing urea splitting and the FeCoNi-LDH material protects CuCo2O4 from corrosion according to experimental results and density functional theory calculations. This experiment provides a new idea for the hydrogen production, exploration and the treatment of urea wastewater for transition metal oxides and layered hydroxides electrocatalyst with core-shell heterostructure.

Biochar catalysts from animal manure: Production and application

Biochar is a sustainable functional material rich in carbon, derived from renewable resources such as biowaste (e.g., animal manure). It has unique chemical structure, large surface area and porosity, and tailored surface functional groups via proper activation and/or functionalization, thereby having high potential as heterogeneous catalytic materials applied to different chemical processes. Therefore, using animal manure-derived biochar as catalytic materials could be key to sustainable agriculture and chemical industries. Recent recognition of animal manure-derived biochars as versatile media of catalytic applications has encouraged rudimentary studies on their catalytic capabilities; however, the use of animal manure-derived biochar as catalytic materials has not been systematically reviewed yet. This review gives an overview of recent achievements in producing biochar from animal manure and subsequent modification methods. The catalytic properties of the biochar with respect to its production/modification recipes are also discussed. Furthermore, the catalytic performances of animal manure-derived biochars for different catalytic applications, such as transesterification, hydrogen production, hydrolysis, C–C coupling reactions, and electrodes for oxygen reduction reaction, supercapacitor, and lithium-ion battery, are evaluated.

DFT study on zeolites’ intrinsic Brønsted acidity: The case of BEA

Since Brønsted acidity is a crucial aspect for the applications of zeolitic materials in heterogeneous catalysis, great effort was devolved to characterize the number, strength and location of the potentially active acidic sites. Quantum chemical calculations can turn out essential in estimating the intrinsic acidity by computing deprotonation energy (DPE) values, although each method comes with its own difficulties. In this context, three approaches within density functional theory were employed to study the intrinsic acidity of 30 topologically distinct Brønsted sites in the β-zeolite framework. Advantages and disadvantages of the three methods were outlined and the acidity order between the sites was assessed, being the DPE range 59 kJ mol−1 wide, with the proposed best approach. By dividing the range into three portions, the sites were classified as having high, medium and low acidity. Hydrogen bonds formation was found to be a contributing factor in determining a low Brønsted acidity.

Diamide-linked imidazolyl Poly(dicationic ionic liquid)s for the conversion of CO2 to cyclic carbonates under ambient pressure

The ionic active centers and hydrogen-bond donors (HBDs) in heterogeneous catalytic materials are highly beneficial for enhancing the interaction between solid–liquid-gas three-phase interfaces and promoting effective fixation of carbon dioxide (CO2). Diamide-linked imidazolyl poly(dicationic ionic liquid)s catalysts PIMDILs (PMAIL-x and PBAIL-2) were synthesized through the copolymerization of diamide-linked imidazolyl dicationic ionic liquids (IMDILs) with divinylbenzene (DVB), which successfully enable the simultaneous construction of high-density and uniformly distributed ionic active centers (2.014–4.883 mmol g−1) and hydrogen-bond donors (HBDs). The as-synthesized PIMDILs present excellent catalytic activity in promoting the cycloaddition of CO2 with epoxides. PMAIL-2 could convert epichlorohydrin (ECH) with a quantitative conversion of 99.8 % (selectivity > 99 %) under ambient pressure. Furthermore, only a decrease in activity of 5 % was observed even after six cycles of recycling. The excellent conversions (>97.3 %) were achieved for various terminal substituted epoxides. The experimental and characterization results reveal that the high-density ionic active centers and amide HBDs can effectively activate the reaction substrates, their synergistic effect plays a crucial role at the catalyst interface. This work is expected to provide some useful insights for the rational construction of heterogeneous catalysts for CO2 conversion.

Effect of morphology and their oxygen vacancies of nanostructured CeO2 catalyst for carboxymethylation of biomass-derived alcohols

An effective and highly selective protocol has been realized for the synthesis of asymmetric organic carbonates using dimethyl carbonate (DMC) as a reactant and solvent. Herein, the performance of CeO2 nanostructures with different morphology was explored in the carbonate interchange reaction (CIR) of alcohols to synthesize asymmetric organic carbonates. The CeO2 nano-catalyst with rod morphology having the highest oxygen vacancy enabled remarkable enhancement in the conversion, to our knowledge this is superior to most of the reported heterogeneous catalytic materials. The CeO2-r (r-rods) is used as low as <0.8 mol% with respect to the limiting reagent (alcohol). The CeO2 characterization data revealed the intriguing properties such as exposed active sites, defect density, coordination state of surface atoms, and reducibility of the catalytic materials are the contributing factors in realizing the highest catalytic activity. The CeO2 was recovered by a simple centrifugation and used in more than four recycles with consistent catalytic activity. The work conducted herein intensifies the utilization of bio-alcohols and CO2 derived DMC for the sustainable synthesis of organic carbonates that have immense applications in various sectors.

Hierarchical porous structure of urushiol mediated Fe3O4/three-dimensional graphene composites towards enhanced Fenton degradation of tetracycline

The Fenton like catalyst Fe3O4 is still limited in wastewater treatment due to its narrow pH range, metal shedding and low catalytic efficiency. Here, a robust urushiol mediated Fe3O4/three-dimensional (3D) graphene was proposed to tackle these challenges. Fe3O4/3D-PU-G (H) was established by loading dense Fe3O4 nanoparticles onto urushiol functionalized 3D graphene via simple solvothermal and mild post-heating. It exhibited rapid degradation (50.3% in 10 s, 97.3% in 10 mins) and reusability (86.8% after 7 cycles) of tetracycline (TC) in a wide pH range (3–11) and various waste water samples. Such excellent performance was attributed to the formation of a stable and compact 3D porous conductive network, which promotes the electron transfer between Fe species and H2O2, the activation of H2O2 to generate OH and the reaction between OH and TC. This work provides a feasible approach for the preparation of efficient heterogeneous catalytic materials.

Degradation of Lignin Pollutants by Persulfate Activated with a Graphene Oxide Loaded Cu2(OH)3NO3 Composite

AbstractGraphene oxide (GO)‐Cu2(OH)3NO3 composite was prepared by a thermal calcination process and evaluated as an effective heterogeneous catalytic material. The composite displayed prominent activated performance to persulfate, which was influenced by preparation condition and the reaction parameters in catalytic system. Under optimal reactive conditions, the GO‐Cu2(OH)3NO3 composite yielded rapid degradation of ferulic acid, which the corresponding apparent rate constant was 1.12×10−1 min−1. Catalytic mechanism analysis showed that the main oxygen species were ⋅SO4− and ⋅OH. Among them, ⋅OH made the main contribution in the catalytic system. The analysis of degradation intermediates of ferulic acid showed that the compound could be mineralized to small molecules. The remarkable enhanced heterogeneous catalytic performance of GO‐Cu2(OH)3NO3 was due to a larger specific surface area, high adsorption capacity and a high mass transfer efficiency of oxidizing radicals in the reactive system.

Intermetallic Pd-Sn Nanoparticles on Supports with High Metal Loading Facilitated by the Metal-Metal Bond for High-Performance Cooperative Catalysis.

Atomically monodispersed intermetallic catalysts comprising highly accessible active sites are ideal heterogeneous catalytic materials. Designing such types of nanocatalysts on carbonaceous supports with high loading, however, remains a formidable challenge. Demonstrated herein is an effective synthetic strategy to produce highly dispersed intermetallic Pd-Sn nanoparticles on various supports with high catalyst loading (upto 24 wt % Pd and 18 wt % Sn) using a discrete bimetallic Pd-Sn complex, which in turn is highly superior as compared to conventionally used methods using individual metal salts. Synergistic cooperative interaction between sub-5 nm Pd-rich particles, supports, and large intermetallic Pd-Sn particles allowed their electronic cross-talk, displaying a much higher reaction efficiency with an entirely different selectivity toward a product, which is highly unlikely in the case of comparable individual components or sequentially impregnated bimetallic materials involving in a catalytic/photocatalytic dehydrogenation, hydrogenation, tandem (de)hydrogenation, and amidation reaction. The designed synthetic strategy has the potential to contribute to the development of atomically monodispersed intermetallic high-loading functional materials for advanced electro- and photocatalytic applications.

PtFeCoNiCu High-Entropy Alloy Catalyst for Aqueous-Phase Hydrogenation of Maleic Anhydride

High-entropy alloys (HEAs), as new heterogeneous catalytic materials, possess remarkable catalytic performance in numerous reactions. However, rational and controllable synthesis of these complex structures remains a challenge. In this work, bulk and carbon nanotube (CNT)-supported ultrasmall PtFeCoNiCu HEA nanoparticles with an average particle size of 1.58 nm are prepared by lithium naphthalenide-driven reduction under mild conditions. The supported PtFeCoNiCu/CNT catalyst exhibits high catalytic activity in the aqueous-phase hydrogenation of maleic anhydride to succinic acid with a selectivity of 98% at full conversion of maleic acid (the hydrolysis product of maleic anhydride), a low apparent activation energy (Ea = 49 kJ mol-1), and excellent stability. Moreover, a much higher mass-specific activity of Pt in the catalyst is displayed over PtFeCoNiCu/CNT (1515.4 mmolmaleicacid gPt-1 h-1) than that of 5 wt % Pt/CNT (388.0 mmolmaleicacid gPt-1 h-1). This work provides a strong support for HEAs as advanced heterogeneous catalysts and will be of great significance for promoting the research and application of HEAs in the field of selective hydrogenation.

MOF-5@Ni Derived ZnO@Ni3ZnC0.7/PMS System for Organic Matter Removal: A Thorough Understanding of the Adsorption–Degradation Process

• ZnO@Ni 3 ZnC 0.7 was successfully synthesized as an effective adsorbent and oxidation catalyst. • Surface hydroxyl groups are the key active sites of both adsorption and degradation. • The degradation process regenerates the adsorption capacity of the catalyst. • Non-radical pathway is the main pathway of degradation in ZN-CS/PMS system. • The magnetic composite can be easily separated and the reusability was verified excellent. The heterogeneous catalytic activation of peroxymonosulfate for wastewater treatment is attracting increased research interest. Therefore, it is essential to find a sustainable, economical, and effective activated material for wastewater treatment. In this study, metal–organic frameworks (MOF)-5 was used as the precursor, and a stable and recyclable material ZnO@Ni 3 ZnC 0.7 that exhibited good adsorption and catalytic properties, was obtained by the addition of nickel and subsequent calcination. To investigate and optimize the practical application conditions, the elimination of rhodamine B (RhB) in water was selected as the model process. This study demonstrated that the degradation of organic matter in the system involved a coupling of the adsorption and degradation processes. Based on this, the mechanism of the entire process was proposed. The results of scanning electron microscopy, infrared spectrum analysis, and theoretical analysis confirmed that the van der Waals forces, electrostatic attraction, and hydrogen bonding influenced the adsorption process. Electron paramagnetic resonance analysis, masking experiments, and electrochemical tests conducted during the oxidative degradation process confirmed that the degradation mechanism of RhB included both radical and non-free radical pathways, and that the surface hydroxyl group was the key active site. The degradation of the adsorbed substrates enabled the regeneration of the active sites. The material regenerated using a simple method exhibited good efficiency for the removal of organic compounds in four-cycle tests. Moreover, this material can effectively remove a variety of organic pollutants, and can be easily recovered owing to its magnetic properties. The results demonstrated that the use of heterogeneous catalytic materials with good adsorption capacity could be an economical and beneficial strategy.

Molecular Views on Mechanisms of Brønsted Acid-Catalyzed Reactions in Zeolites.

The Brønsted acidity of proton-exchanged zeolites has historically led to the most impactful applications of these materials in heterogeneous catalysis, mainly in the fields of transformations of hydrocarbons and oxygenates. Unravelling the mechanisms at the atomic scale of these transformations has been the object of tremendous efforts in the last decades. Such investigations have extended our fundamental knowledge about the respective roles of acidity and confinement in the catalytic properties of proton exchanged zeolites. The emerging concepts are of general relevance at the crossroad of heterogeneous catalysis and molecular chemistry. In the present review, emphasis is given to molecular views on the mechanism of generic transformations catalyzed by Brønsted acid sites of zeolites, combining the information gained from advanced kinetic analysis, in situ, and operando spectroscopies, and quantum chemistry calculations. After reviewing the current knowledge on the nature of the Brønsted acid sites themselves, and the key parameters in catalysis by zeolites, a focus is made on reactions undergone by alkenes, alkanes, aromatic molecules, alcohols, and polyhydroxy molecules. Elementary events of C-C, C-H, and C-O bond breaking and formation are at the core of these reactions. Outlooks are given to take up the future challenges in the field, aiming at getting ever more accurate views on these mechanisms, and as the ultimate goal, to provide rational tools for the design of improved zeolite-based Brønsted acid catalysts.

Cyclic extrusion synthesis of mesoporous carbon‐supported metal catalysts for selective hydrogenation

AbstractThe mesoporous carbon‐supported metal catalysts are important materials in heterogeneous catalysis. From the standpoint of process intensification, the current synthesis methods still suffer from several issues, such as the excessive use of toxic solvents, the time‐consuming self‐assembly process, and the difficulty of continuous production. Herein, we report a solvent‐free and continuous route to synthesize mesoporous carbon‐supported metal catalysts. Interestingly, the use of cyclic extrusion could promote mixing, coordination, and assembly of catalyst precursors (tannin‐metal salts‐additives) by shearing and squeeze force. The as‐made mesoporous carbon‐supported nickel materials showed high surface areas (up to 512 m2 g−1), narrow pore size distribution (~10 nm), and good performance in the selective hydrogenation of nitrobenzene to aniline (Conv. &gt;99%; Sel. &gt;99%). In addition, the fluid property of catalyst precursors and the geometry of the twin‐screw extrusion channel were studied, and the essence of this cyclic extrusion process is also discussed.

Homogeneous versus MOF-supported catalysis: a direct comparison of catalytic hydroboration with Ni tripodal P3E (E = Si, Ge) complexes.

The MOF material NU-1000 was employed to host Ni tripodal complexes prepared from new organometallic precursors [HNi(κ4(E,P,P,P)-E(o-C6H4CH2PPh2)3], E = Si (Ni-1), Ge (Ni-2). The new heterogeneous catalytic materials, Ni-1@NU-1000 and Ni-2@NU-1000, show the advantages of both homogeneous and heterogeneous catalysts. They catalyze the hydroboration of aldehydes and ketones more efficiently than the homogeneous Ni-1 and Ni-2, under aerobic conditions and show recyclability.

Biomass-Derived Carbon Materials in Heterogeneous Catalysis: A Step towards Sustainable Future

Biomass-derived carbons are emerging materials with a wide range of catalytic properties, such as large surface area and porosity, which make them ideal candidates to be used as heterogeneous catalysts and catalytic supports. Their unique physical and chemical properties, such as their tunable surface, chemical inertness, and hydrophobicity, along with being environmentally friendly and cost effective, give them an edge over other catalysts. The biomass-derived carbon materials are compatible with a wide range of reactions including organic transformations, electrocatalytic reactions, and photocatalytic reactions. This review discusses the uses of materials produced from biomass in the realm of heterogeneous catalysis, highlighting the different types of carbon materials derived from biomass that are potential catalysts, and the importance and unique properties of heterogeneous catalysts with different preparation methods are summarized. Furthermore, this review article presents the relevant work carried out in recent years where unique biomass-derived materials are used as heterogeneous catalysts and their contribution to the field of catalysis. The challenges and potential prospects of heterogeneous catalysis are also discussed.

Toward Sabatier Optimal for Ammonia Synthesis with Paramagnetic Phase of Ferromagnetic Transition Metal Catalysts.

The Sabatier principle defines the essential criteria for being an ideal catalyst in heterogeneous catalysis, while approaching the Sabatier optimal is a major pursuit in catalyst design. The Haber-Bosch (H-B) process, converting nitrogen (N2) and hydrogen (H2) to ammonia (NH3), is a holy grail reaction for humans and also a great model reaction for fundamental research, where the established volcano plot between ammonia synthesis activity and nitrogen binding energy among metals has successfully guided new catalyst design. However, reaching the top of the activity volcano is still very challenging. Herein, we identify an elegant strategy to promote the ferromagnetic (FM) catalysts to be the Sabatier optimal of ammonia synthesis via a second-order ferromagnetic-paramagnetic phase transition, which represents an ideal and novel interdisciplinary of the aforementioned century-old classic principle, reaction, and theory in chemistry, physics, and material science. The paramagnetic (PM) Co and Ni metals could have 2-4 orders of magnitude higher ammonia synthesis activity than their ferromagnetic counterparts, holding the potential to achieve a near-ambient H-B process. We believe that our discovery will open a novel avenue for revisiting the catalytic performances of paramagnetic phases of ferromagnetic materials in heterogeneous catalysis.