CO2 reduction to formic acid via NH2-C@Cu2O photocatalyst in situ derived from amino modified Cu-MOF

Enhancing CO2 photoreduction to CO with 100 % selectivity by constructing heterojunctions and regulating open metal sites in Au/Fe3O4/MIL-101(Fe) catalysts

The widespread utilization of fossil fuels has resulted in a significant increase in CO2 emissions, leading to a variety of environmental issues. The photocatalytic conversion of CO2 into fuel presents an effective solution to both the energy crisis and environmental warming. Therefore, the selection of a suitable catalyst is paramount. However, traditional photocatalysts often encounter challenges such as rapid electron-hole recombination and limited exposure of active sites. To improve these limitations, this study introduces AFM-X, a heterojunction catalyst composed of Au/Fe3O4/MIL-101(Fe)-X, which facilitates the formation of open metal sites (OMS) that enhance the effective separation of photogenerated carriers. In AFM-X, OMS function as Lewis acid sites, thereby enhancing CO2 adsorption. The presence of Au nanoparticles (NPs) introduces additional active sites for CO2 reduction. The synergistic effect between OMS and Au NPs increases the catalyst's active sites, while the heterojunction construction promotes electron transfer, thereby enhancing CO2 photocatalytic reduction efficiency. The CO generation rate of AFM-2 reached 98.8 μmol g-1 h-1, surpassing those of FM, MIL-101(Fe), Fe3O4, and Au NPs, by 4.1, 6.3, 6.2, and 3.2 times, respectively. Furthermore, AFM-2 maintains stable performance over a 40 h cycle test. In-situ DRIFTS spectroscopy reveals that CO2 reduction occurs through two parallel pathways. This study offers new insights into the design of composite photocatalytic materials, highlighting the effectiveness of OMS Lewis acid sites in significantly enhancing the photocatalytic reduction of CO2.

Revealing the Mechanism of Converting CO2 into Methanol by the Cu2O and Oxygen Vacancy on MgO: Experiments and Density Functional Theory

Given the great significance of defect and Cu compounds for the reduction of CO2 as well as the few reaction mechanisms of converting CO2 into different hydrocarbons, the effects of oxygen vacancies and Cu2O on the reduction of CO2 were thoroughly investigated, and possible mechanisms were also proposed. A series of Cu2O/Ov-MgO catalysts were synthesized for photothermal catalytic reduction of CO2 to methanol under visible-light irradiation, among which the 7%Cu2O/Ov-MgO composite exhibited the best reduction activity and the yield of methanol was 19.78 μmol·g-1·h-1. The successful composite of Cu2O and Ov-MgO can yield a loose and porous nanosheet, uniform distribution, favorable absorbance and photoelectric performance, and increased specific surface area and adsorption ability of CO2, which are all vital to the adsorption and conversion of CO2. The introduction of oxygen vacancy and Cu2O not only promotes the adsorption of CO2 but also provides more electron-triggered CO2 activation. Density functional theory (DFT) calculation was also performed to reveal the reaction mechanism for effective enhanced CO2 reduction to ethanol or methanol by the comparison of CuO/MgO and Cu2O/Ov-MgO composites, illustrating the reaction pathways of different products. By comparing the key steps in determining the selectivity of C1 or C2, the kinetic barriers of obtaining CH3OH for the Cu2O/Ov-MgO composite with CH3OH as the main product were found to be lower than those of generating CH2*, while the opposite is true for CuO/MgO composites, whereby it may be easier to obtain more C2 products. These insights into the reaction mechanism of converting CO2 into different hydrocarbons are expected to provide guidance for the further design of high-performance photothermal catalytic CO2 reduction catalysts.

Metallic 1T-N-WS2 /WO3 Heterojunctions Featuring Interface-Engineered Cu-S Configuration for Selective Electrochemical CO2 Reduction Reaction

Electrocatalytic carbon-dioxide reduction reactions (ECO2 RR) are one of the most rational techniques to control one's carbon footprint. The desired product formation depends on deliberate reaction kinetics and a choice of electron-proton contribution. Herein the usage of novel CuS active centers decorated over stable 1T metallic N-WS2 /WO3 nanohybrids as an efficient selective formate conversion electrocatalyst with regard to ECO2 RR is reported. The preferred reaction pathway is identified as *OCHO, which is reduced (by gaining H+  + e- ) to HCOO- (HCOO- path) as the primary product. More significantly, at -1.3 V versus RHE yield of FEHCOO - is 55.6% ± 0.5 with a Jgeo of -125.05 mA cm-2 for CuS@1T-N-WS2 /WO3 nanohybrids. In addition, predominant catalytic activity, selectivity, and stability properties are observed; further post-mortem analysis demonstrates the choice of material importance. The present work describes an impressive approach to develop highly active electrocatalysts for selective ECO2 RR applications.

A Review on Cu2O-Based Composites in Photocatalysis: Synthesis, Modification, and Applications

Photocatalysis technology has the advantages of being green, clean, and environmentally friendly, and has been widely used in CO₂ reduction, hydrolytic hydrogen production, and the degradation of pollutants in water. Cu₂O has the advantages of abundant reserves, a low cost, and environmental friendliness. Based on the narrow bandgap and strong visible light absorption ability of Cu₂O, Cu₂O-based composite materials show infinite development potential in photocatalysis. However, in practical large-scale applications, Cu₂O-based composites still pose some urgent problems that need to be solved, such as the high composite rate of photogenerated carriers, and poor photocatalytic activity. This paper introduces a series of Cu₂O-based composites, based on recent reports, including pure Cu₂O and Cu₂O hybrid materials. The modification strategies of photocatalysts, critical physical and chemical parameters of photocatalytic reactions, and the mechanism for the synergistic improvement of photocatalytic performance are investigated and explored. In addition, the application and photocatalytic performance of Cu₂O-based photocatalysts in CO₂ photoreduction, hydrogen production, and water pollution treatment are discussed and evaluated. Finally, the current challenges and development prospects are pointed out, to provide guidance in applying Cu₂O-based catalysts in renewable energy utilization and environmental protection.

Converting CO2 into Value-Added Products by Cu2 O-Based Catalysts: From Photocatalysis, Electrocatalysis to Photoelectrocatalysis

Converting CO₂ into value-added products by photocatalysis, electrocatalysis, and photoelectrocatalysis is a promising method to alleviate the global environmental problems and energy crisis. Among the semiconductor materials applied in CO₂ catalytic reduction, Cu₂ O has the advantages of abundant reserves, low price and environmental friendliness. Moreover, Cu₂ O has unique adsorption and activation properties for CO₂ , which is conducive to the generation of C₂₊ products through CC coupling. This review introduces the basic principles of CO₂ reduction and summarizes the pathways for the generation of C₁ , C₂ , and C₂₊ products. The factors affecting CO₂ reduction performance are further discussed from the perspective of the reaction environment, medium, and novel reactor design. Then, the properties of Cu₂ O-based catalysts in CO₂ reduction are summarized and several optimization strategies to enhance their stability and redox capacity are discussed. Subsequently, the application of Cu₂ O-based catalysts in photocatalytic, electrocatalytic, and photoelectrocatalytic CO₂ reduction is described. Finally, the opportunities, challenges and several research directions of Cu₂ O-based catalysts in the field of CO₂ catalytic reduction are presented, which is guidance for its wide application in the energy and environmental fields is provided.

A CuI Cluster-Based Covalent Metal-Organic Framework as a Photocatalyst for Efficient Visible-Light-Driven Reduction of CO2

The application of solar energy to convert CO₂ into high-value chemicals and fuels has been considered a highly desirable approach to relieving the greenhouse effect and energy crisis. However, the exploration of appropriate photocatalysts remains a major challenge. Combining the respective advantages of covalent organic frameworks and metal-organic frameworks to construct covalent metal-organic frameworks (CMOFs) can be a valid strategy to provide efficient, reliable, and eco-friendly photocatalysts. In this study, a Cu^I cluster-based CMOF (JNM-2) is used as a photocatalyst for CO₂ photoreduction under visible-light irradiation. JNM-2 exhibits remarkable efficiency in photocatalytic CO₂ reduction with high production rates of HCOOH (9019 μmol g^-1  h^-1 ) and CO (835 μmol g^-1  h^-1 ). The active center, reaction intermediates, and product generation pathways are elucidated by in situ DRIFTS and DFT calculations. This work demonstrates the tremendous possibilities of CMOFs as photocatalysts for CO₂ reduction and provides profound insights into the mechanism of CO₂ conversion into HCOOH/CO by using a molecularly accurate structural model.

Rational Construction of Metal Organic Framework Hybrid Assemblies for Visible Light-Driven CO2 Conversion

Photocatalytic reduction of CO₂ to value-added chemicals is known to be a promising approach for CO₂ conversion. The design and preparation of ideal photocatalysts for CO₂ conversion are of pivotal significance for the sustainable development of the whole society. In this work, we integrated two functional organic linkers to prepare a novel metal organic framework (MOF) photocatalyst {[Co(9,10-bis(4-pyridyl)anthracene)_0.5(bpda)]·4DMF} (Co-MOF). The existence of anthryl and amino groups leads to a wide range of visible light absorption and efficient separation of photogenerated electrons. To extend the lifetime of photogenerated electrons in the photocatalytic system, we modified Co-MOF particles onto g-C₃N₄. As expected, Co-MOF/g-C₃N₄ composites exhibited an ultrahigh selectivity (more than 97%) in the photocatalytic process, and the highest CO production rate (1824 μmol/g/h) was 7.1 and 27.2 times of Co-MOFs and g-C₃N₄, respectively. What's more, we also discussed the reaction mechanism of the Co-MOF/g-C₃N₄ photocatalytic CO₂ reduction, and this work paves the pathway for designing photocatalysts with ideal CO₂ reduction performance.

A p-n Junction by Coupling Amine-Enriched Brookite-TiO2 Nanorods with CuxS Nanoparticles for Improved Photocatalytic CO2 Reduction

Photocatalytic CO₂ reduction is a promising technology for reaching the aim of "carbon peaking and carbon neutrality", and it is crucial to design efficient photocatalysts with a rational surface and interface tailoring. Considering that amine modification on the surface of the photocatalyst could offer a favorable impact on the adsorption and activation of CO₂, in this work, amine-modified brookite TiO₂ nanorods (NH₂-B-TiO₂) coupled with Cu_xS (NH₂-B-TiO₂-Cu_xS) were effectively fabricated via a facile refluxing method. The formation of a p-n junction at the interface between the NH₂-B-TiO₂ and the Cu_xS could facilitate the separation and transfer of photogenerated carriers. Consequently, under light irradiation for 4 h, when the Cu_xS content is 16%, the maximum performance for conversion of CO₂ to CH₄ reaches at a rate of 3.34 μmol g^-1 h^-1 in the NH₂-B-TiO₂-Cu_xS composite, which is approximately 4 times greater than that of pure NH₂-B-TiO₂. It is hoped that this work could deliver an approach to construct an amine-enriched p-n junction for efficient CO₂ photoreduction.

Advances in Biomimetic Photoelectrocatalytic Reduction of Carbon Dioxide

Emerging photoelectrocatalysis (PEC) systems synergize the advantages of electrocatalysis (EC) and photocatalysis (PC) and are considered a green and efficient approach to CO2 conversion. However, improving the selectivity and conversion rate remains a major challenge. Strategies mimicking natural photosynthesis provide a prospective way to convert CO2 with high efficiency. Herein, several typical strategies are described for constructing biomimetic photoelectric functional interfaces; such interfaces include metal cocatalysts/semiconductors, small molecules/semiconductors, molecular catalysts/semiconductors, MOFs/semiconductors, and microorganisms/semiconductors. The biomimetic PEC interface must have enhanced CO2 adsorption capacity, preferentially activate CO2 , and have an efficient conversion ability; with these properties, it can activate CO bonds effectively and promote electron transfer and CC coupling to convert CO2 to single-carbon or multicarbon products. Interfacial electron transfer and proton coupling on the biomimetic PEC interface are also discussed to clarify the mechanism of CO2 reduction. Finally, the existing challenges and perspectives for biomimetic photoelectrocatalytic CO2 reduction are presented.

High selectivity of photocatalytic reduction of CO2 to CO based on terpyridine ligand supported CuI metal organic framework

In this work, a 4'-(4-cynaophenyl)-4,2':6',4-terpyridine supported CuI MOFs photocatalyst (Cu I MOF) was applied to the photocatalytic CO2 reduction for the first time. The micro-structural and physicochemical properties of the Cu I MOF were systematically studied by the powder X-ray diffraction (PXRD), Single crystal X-ray diffraction (SCXRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), UV-Vis diffuse spectroscopy (UV-vis DRS), ns-level photoluminescence spectra (ns-level PL), Ultraviolet photoelectron spectroscopy (UPS), and N2 adsorption-desorption test (BET-BJH). Moreover, the in situ diffuse reflectance infrared fourier transform spectroscopy (in situ DRIFTS) was applied to investigate the adsorption and reaction intermediates of photocatalytic CO2 reduction. As a result, Cu I MOF exhibited good performance and outstanding selectivity toward photocatalytic reduction of CO2 to CO under full-spectrum and visible light illumination. Notably, 100% selective photocatalytic conversion of CO2 to CO was achieved. Thus, the study presents the high selectivity and CO2 reduction efficiency of Cu I MOF as a potential family of photocatalysts.