MOF-derived ceria-zirconia supported Co3O4 catalysts with enhanced activity in CO2 methanation

Research progress on metal-organic framework compounds (MOFs) in electrocatalysis

Metal-organic frameworks (MOFs) have favorable characteristics such as large specific surface area, high porosity, structural diversity, and pore surface modification, giving them great potential for development and attractive prospects in the research area of modern materials electrocatalysis. However, unsatisfactory catalytic activity and poor electronic conductivity are the main challenges facing MOFs. This review focuses on MOF-based materials used in electrocatalysis, based on the types of catalytic reactions that have used MOF-based materials in recent years along with their applications, and also looks at some new electrocatalytic materials and their future development prospects.

Bimetallic Copper-Cerium-Based Metal-Organic Frameworks for Selective Carbon Dioxide Capture

Metal-organic frameworks (MOFs) are highly regarded as valuable adsorbent materials in materials science, particularly in the field of CO2 capture. While numerous single-metal-based MOFs have demonstrated exceptional CO2 adsorption capabilities, recent advancements have explored the potential of bimetallic MOFs for enhanced performance. In this study, a CuCe-BTC MOF was synthesized through a straightforward hydrothermal method, and its improved properties, such as high surface area, smaller pore size, and larger pore volume, were compared with those of the bare Ce-BTC. The impact of the Cu/Ce ratio (1:4, 1:2, 1:1, and 3:2) was systematically investigated to understand how adding a second metal influences the CO2 adsorption performance of the Ce-BTC MOF. Various characterization techniques, including scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and N2 BET surface area analysis, were employed to assess the physical and chemical properties of the bare Ce-BTC and CuCe-BTC samples. Notably, CuCe-BTC-1:2 exhibited superior surface area (133 m2 g-1), small pore size (3.3 nm), and large pore volume (0.14 cm3 g-1) compared to the monometallic Ce-BTC. Furthermore, CuCe-BTC-1:2 demonstrated a superior CO2 adsorption capacity (0.74 mmol g-1), long-term stability, and good CO2/N2 selectivity. This research provides valuable insights into the design of metal-BTC frameworks and elucidates how introducing a second metal enhances the properties of the monometallic Ce-BTC-MOF, leading to improved CO2 capture performance.

Synthesis of Cobalt-Based Nanoparticles as Catalysts for Methanol Synthesis from CO2 Hydrogenation

The increasing emission of carbon dioxide into the atmosphere has urged the scientific community to investigate alternatives to alleviate such emissions, being that they are the principal contributor to the greenhouse gas effect. One major alternative is carbon capture and utilization (CCU) toward the production of value-added chemicals using diverse technologies. This work aims at the study of the catalytic potential of different cobalt-derived nanoparticles for methanol synthesis from carbon dioxide hydrogenation. Thanks to its abundance and cost efficacy, cobalt can serve as an economical catalyst compared to noble metal-based catalysts. In this work, we present a systematic comparison among different cobalt and cobalt oxide nanocomposites in terms of their efficiency as catalysts for carbon dioxide hydrogenation to methanol as well as how different supports, zeolites, MnO2, and CeO2, can enhance their catalytic capacity. The oxygen vacancies in the cerium oxide act as carbon dioxide adsorption and activation sites, which facilitates a higher methanol production yield.

Synergistic Effect of Nickel Nanoparticles Dispersed on MOF-Derived Defective Co3O4 In Situ Grown over TiO2 Nanowires toward UV and Visible Light Driven Photothermal CO2 Methanation

Catalytic CO2 hydrogenation is an effective approach to producing clean fuels, but this process is expensive, in addition to the low efficiency of catalysts. Thus, photothermal CO2 hydrogenation can effectively utilize solar energy for CH4 production. Metal-organic framework (MOF) derived materials with a controlled structure and morphology are promising to give a high number of active sites and photostability in thermal catalytic reactions. For the first time, a novel heterostructure catalyst was synthesized using a facile approach to in situ grow MOF-derived 0D Co3O4 over 1D TiO2 nanowires (NWs). The original 3D dodecahedral structure of the MOF is engineered into novel 0D Co3O4 nanospheres, which were uniformly embedded over Ni-dispersed 1D TiO2 NWs. In situ prepared 10Ni-7Co3O4@TiO2 NWs-I achieved an excellent photothermal CH4 evolution rate of 8.28 mmol/h at 250 °C under low-intensity visible light, whereas UV light treatment further increased activity by 1.2-fold. UV irradiations promoted high CH4 production while improving the susceptibility of the catalyst to visible light irradiation. The photothermal effect is prominent at lower temperatures, due to the harmonization of both solar and thermal energy. By paralleling with mechanically assembled 10Ni-7Co3O4/TiO2 NWs-M, the catalytic performance of the in situ approach is far superior, attributing to the morphological transformation of 0D Co3O4, which induced intimate interfacial interactions, formation of oxygen vacancies and boosted photo-to-thermal effects. The co-existence of metallic/metal oxide Ni-Co provided beneficial synergies, enhanced photo-to-thermal effects, and improved charge transfer kinetics of the composite. This work uncovers a facile approach to engineering the morphology of MOF derivatives for efficient photothermal CO2 methanation.

MOF-derived transition metal-based catalysts for the electrochemical reduction of CO2 to CO: a mini review

The excessive emission of CO₂ derived from the consumption of fossil fuels has caused severe energy and environmental crises. The electrochemical reduction of CO₂ into value-added products such as CO not only reduces the CO₂ concentration in the atmosphere but also promotes sustainable development in chemical engineering. Thus, tremendous work has been devoted to developing highly efficient catalysts for the selective CO₂ reduction reaction (CO₂RR). Recently, MOF-derived transition metal-based catalysts have shown great potential for the CO₂RR due to their various compositions, adjustable structures, competitive ability, and acceptable cost. Herein, based on our work, a mini-review is proposed for an MOF-derived transition metal-based catalyst for the electrochemical reduction of CO₂ to CO. The catalytic mechanism of the CO₂RR was first introduced, and then we summarized and analyzed the MOF-derived transition metal-based catalysts in terms of MOF-derived single atomic metal-based catalysts and MOF-derived metal nanoparticle-based catalysts. Finally, we present the challenges and perspectives for the subject topic. Hopefully, this review could be helpful and instructive for the design and application of MOF-derived transition metal-based catalysts for the selective CO₂RR to CO.

A simple method for the preparation of CeO2with high antioxidant activity and wide application range

Cerium oxide (CeO₂) is a well-known antioxidant with the ability to scavenge reactive oxygen species due to its unique electronic structure and chemical properties. Although many methods to enhance the antioxidant activity of CeO₂have been reported, its antioxidant activity is still not high enough, and some enhancement effects are limited by the material concentration. There are also some CeO₂obtained with high antioxidant activity at high concentrations, which is not conducive to the application of biomedicine. Therefore, it is urgent to obtain CeO₂material with low cell cytotoxicity, high antioxidant activity and wide application range. In this work, rod-like metal organic framework derived CeO₂(CeO₂-MOF) was prepared by a simple method. Compared with the CeO₂nanorods prepared by hydrothermal method, it shows better antioxidant activity compared with the CeO₂nanorods prepared by hydrothermal method. Moreover, the advantage of CeO₂-MOF's antioxidant activity is not affected by the hydroxyl radical and material concentrations The reason why CeO₂-MOF has higher antioxidant activity should be attributed to its higher Ce³⁺content and larger specific surface area. In addition, CeO₂-MOF also exhibits low cytotoxicity to HeLa cells and PC12 cellsin vitro. The strategy of using MOF as a structural and compositional material to create CeO₂provides a new method to explore highly efficient and biocompatible CeO₂for practical applications.

Cerium d-Block Element (Co, Ni) Bimetallic Oxides as Catalysts for the Methanation of CO2: Effect of Pressure

Nickel– and cobalt–cerium bimetallic oxides were used as catalysts for the methanation of CO2 under pressure. The catalysts’ activity increases with pressure and an increase of just 10 bar is enough to double the yield of methane and to significantly improve the selectivity. The best results were those obtained over nickel–cerium bimetallic oxides, but the effect of pressure was particularly relevant over cobalt–cerium bimetallic oxides, which yield to methane increases from almost zero at atmospheric pressure to 50–60% at 30 bar. Both catalyst types are remarkably competitive, especially those containing nickel, which were always more active than a commercial rhodium catalyst used as a reference (5wt.% Rh/Al2O3) and tested under the same conditions. For the cobalt–cerium bimetallic oxides, the existence of a synergetic interaction between Co and CoO and the formation of cobalt carbides seems to play an important role in their catalytic behavior. Correlation between experimental reaction rates and simulated data confirms that the catalysts’ behavior follows the Langmuir–Hinshelwood–Hougen–Watson kinetic model, but Le Chatelier’s principle is also important to understand the catalysts’ behavior under pressure. A catalyst recycle study was also performed. The results obtained after five cycles using a nickel–cerium catalyst show insignificant variations in activity and selectivity, which are important for any type of practical application.

CO2 hydrogenation over functional nanoporous polymers and metal-organic frameworks

CO₂ is one of the major environmental pollutants and its mitigation is attracting huge attention over the years due to continuous increase in this greenhouse gas emission in the atmosphere. Being environmentally hazardous and plentiful presence in nature, CO₂ utilization as C1 resource into fuels and feedstock is very demanding from the green chemistry perspectives. To accomplish this CO₂ utilization issue, functional organic materials like porous organic polymers (POPs), covalent organic frameworks (COFs) as well as organic-inorganic hybrid materials like metal-organic frameworks (MOFs), having characteristics of large surface area, high thermal stability and tunability in the porous nanostructures play significant role in designing the suitable catalyst for the CO₂ hydrogenation reactions. Although CO₂ hydrogenation is a widely studied and emerging area of research, till date review exclusively focused on designing POPs, COFs and MOFs bearing reactive functional groups is very limited. A thorough literature review on this matter will enrich our knowledge over the CO₂ hydrogenation processes and the catalytic sites responsible for carrying out these chemical transformations. We emphasize recent state-of-the art developments in POPs/COFs/MOFs having unique functionalities and topologies in stabilizing metallic NPs and molecular complexes for the CO₂ reduction reactions. The major differences between MOFs and porous organics are critically summarized in the outlook section with the aim of the future benefit in mitigating CO₂ emission from ambient air.