Asymmetric Triple-Atom Sites Confined in Ternary Oxide Enabling Selective CO2 Photothermal Reduction to Acetate

Dual Active Sites with Charge-asymmetry in Organic Semiconductors Promoting C-C Coupling for Highly Efficient CO2 Photoreduction to Ethanol

Selective CO2 photoreduction into high-energy-density and high-value-added C2 products is an ideal strategy to achieve carbon neutrality and energy shortage, but it is still highly challenging due to the large energy barrier of the C-C coupling step and severe exciton annihilation in photocatalysts. Herein, strong and localized charge polarization is successfully induced on the surface of melon-based organic semiconductors by creating dual active sites with a large charge asymmetry. Confirmed by multiscale characterization and theoretical simulations, such asymmetric charge distribution, originated from the oxygen dopants and nitrogen vacancies over melon-based organic semiconductors, reduces exciton binding energy and boosts exciton dissociation. The as-formed charge polarization sites not only donate electrons to CO2 molecules but also accelerate the coupling of asymmetric *CO*CO intermediates for CO2 photoreduction into ethanol by lowering the energy barrier of this process. Consequently, an exceptionally high selectivity of up to 97 % for C2H5OH and C2H5OH yield of 0.80 mmol g-1 h-1 have been achieved on this dual active sites organic semiconductor. This work, with its potential applicability to a variety of non-metal multi-site catalysts, represents a versatile strategy for the development of advanced catalysts tailored for CO2 photoreduction reactions.

Enhancing Photocatalytic CO2RR by Modulating the Active Sites of COF-Based Catalysts

The catalytic conversion of CO2 into valuable chemicals using metalized covalent organic frameworks (COFs) as catalysts is a promising method for reducing atmospheric CO2 levels. Herein, a aldehyde-amine COF (TAPT-Tp) at room temperature and pressure and their metallized results is synthesized, Ni-TAPT-Tp and Ti-TAPT-Tp. The photocatalytic results indicate that the CO2 to CO reduction rate is 6182.5 µmol g-1 h-1 for Ni-TAPT-Tp, but only 1615.4 µmol g-1 h-1 for Ti-TAPT-Tp. Density functional theory (DFT) simulations further demonstrate that for intermediates *CO2, *COOH, and *CO, the energy of Ni-TAPT-Tp is consistently lower than that of Ti-TAPT-Tp, indicating that Ni-TAPT-Tp exhibits superior photocatalytic performance for CO2RR. This work provides a reference for optimizing the coordination structure of M-COFs to obtain highly active and selective CO2RR.

Highly Active Photoreduction of Atmospheric-Concentration CO2 into CH3COOH over Palladium Particles on Nb2O5 Nanosheets

The endeavor to drive CO2 photoreduction towards the synthesis of C2 products is largely thwarted by the colossal energy hurdle inherent in C-C coupling. Herein, we load active metal particles on metal oxide nanosheets to build the dual metal pair sites for steering C-C coupling to form C2 products. Taking Pd particles anchored on the Nb2O5 nanosheets as an example, the high-angle annular dark-field image and X-ray photoelectron spectroscopy demonstrate the presence of Pd-Nb metal pair sites on the Pd-Nb2O5 nanosheets. Density functional theory calculations reveal these sites exhibit a low reaction energy barrier of only 1.02 eV for C-C coupling, implying that the introduction of Pd particles effectively tailors the reaction step to form C2 products. Therefore, the Pd-Nb2O5 nanosheets achieve a CH3COOH evolution rate of 13.5 μmol g-1 h-1 in photoreduction of atmospheric-concentration CO2, outshining all other single photocatalysts reported to date under analogous conditions.

Floatable artificial leaf to couple oxygen-tolerant CO2 conversion with water purification

To enable open environment application of artificial photosynthesis, the direct utilization of environmental CO2 via an oxygen-tolerant reductive procedure is necessary. Herein, we introduce an in situ growth strategy for fabricating two-dimensional heterojunctions between indium porphyrin metal-organic framework (In-MOF) and single-layer graphene oxide (GO). Upon illumination, the In-MOF/GO heterostructure facilitates a tandem CO2 capture and photocatalytic reduction on its hydroxylated In-node, prioritizing the reduction of dilute CO2 even in the presence of air-level O2. The In-MOF/GO heterostructure photocatalyst is integrated with a porous polytetrafluoroethylene (PTFE) membrane to construct a floatable artificial leaf. Through a triphase photocatalytic reaction, the floatable artificial leaf can remove aqueous contaminants from real water while efficiently reducing CO2 at low concentrations (10%, approximately the CO2 concentration in combustion flue gases) upon air-level O2. This study provides a scalable approach for the construction of photocatalytic devices for CO2 conversion in open environments.

Photothermal CO2 Catalysis toward the Synthesis of Solar Fuel: From Material and Reactor Engineering to Techno-Economic Analysis

Carbon dioxide (CO2), a member of greenhouse gases, contributes significantly to maintaining a tolerable environment for all living species. However, with the development of modern society and the utilization of fossil fuels, the concentration of atmospheric CO2 has increased to 400 ppm, resulting in a serious greenhouse effect. Thus, converting CO2 into valuable chemicals is highly desired, especially with renewable solar energy, which shows great potential with the manner of photothermal catalysis. In this review, recent advancements in photothermal CO2 conversion are discussed, including the design of catalysts, analysis of mechanisms, engineering of reactors, and the corresponding techno-economic analysis. A guideline for future investigation and the anthropogenic carbon cycle are provided.

Anti-Site Defect-Induced Cascaded Sub-Band Transition in CuInS2 Enables Infrared Light-Driven CO2 Reduction

Photocatalytic CO2 conversion is a promising approach to simultaneously mitigate climate change and alleviate the energy crisis. However, infrared light, which constitutes nearly half of the solar energy, has not been effectively utilized yet. In this work, we discover a photogenerated charge transition mechanism in CuInS2 with intrinsic InCu antisite defects for synergistic utilization of full-spectrum photons. Femtosecond transient absorption spectroscopy and DFT calculation unveil an intermediate band induced by the intrinsic antisite defects, where cascaded sub-band transition could be realized by high-energy photons (UV-vis) and low-energy (IR), thus improving the absorption range of infrared light as well as the utilization efficiency of photogenerated carriers. In situ Kelvin probe force microscopy demonstrates that the generation of photoexcited electrons could be greatly enhanced through this synergistic utilization of full spectrum light. Moreover, in situ X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy reveal that infrared photons could also enhance the adsorption and activation of CO2 and H2O on the catalyst surface. As a result, the CO production rate under full spectrum light reaches 19.9 μmol g-1 h-1, which is more than a 7-fold increase over that under UV-vis irradiation.

Engineering the electron localization of metal sites on nanosheets assembled periodic macropores for CO2 photoreduction

Photocatalytic conversion of CO2 into syngas is highly appealing, yet still suffers from the undesirable product yield due to the sluggish carrier transfer and the uncontrollable affinity between catalytic sites and intermediates. Here we report the fabrication of Co sites with tunable electron localization capability on two dimensional (2D) nanosheets assembled three dimensional (3D) ordered macroporous framework (3DOM-NS). The as-prepared Co-based 3DOM-NS catalysts exhibit attractive photocatalytic performances toward CO2 reduction, among which the cobalt sulfide one (3DOM Co-SNS) shows the highest syngas generation rate up to 347.3 μmol h-1 under the irradiation of visible light and delivers a remarkable catalytic activity (1150.7 μmol h-1) in a flow reaction system under natural sunlight. Mechanism studies reveal that the high electron localization of metal sites in 3DOM Co-SNS strengthens the interaction between Co and HCOO* via the orbital interactions of dyz/dxz-p and s-s, thus facilitating the cleaving process of C-O bond. Additionally, the ordered macroporous framework with nanosheet subunits elevates the transfer efficiency of photoexcited electrons, which contributes to its high activity.

Defect Regulation Strategy of Porous Persistent Phosphors for Multiple and Dynamic Information Encryption

Optical encryption technologies based on persistent luminescence material have currently drawn increasing attention due to the distinctive and long-lived optical properties, which enable multi-dimensional and dynamic optical information encryption to improve the security level. However, the controlled synthesis of persistent phosphors remains largely unexplored and it is still a great challenge to regulate the structure for optical properties optimization, which inevitably sets significant limitations on the practical application of persistent luminescent materials. Herein, a controlled synthesis method is proposed based on defect structure regulation and a series of porous persistent phosphors is obtained with different luminous intensities, lifetime, and wavelengths. By simply using diverse templates during the sol-gel process, the oxygen vacancy defects structures are successfully regulated to improve the optical properties. Additionally, the obtained series of porous Al2O3 are utilized for multi-color and dynamic optical information encryption to increase the security level. Overall, the proposed defect regulation strategy in this work is expected to provide a general and facile method for optimizing the optical properties of persistent luminescent materials, paving new ways for broadening their applications in multi-dimensional and dynamic information encryption.

Bioinspired catalytic pocket promotes CO2-to-ethanol photoconversion on colloidal quantum wells

Sluggish surface reaction is a critical factor that strongly governs the efficiency of photocatalytic solar fuel production, particularly in CO2-to-ethanol photoconversion. Here, inspired by the principles underlying enzyme catalytic proficiency and specificity, we report a biomimetic photocatalyst that affords superior CO2-to-ethanol photoreduction efficiency (5.5 millimoles gram-1 hour-1 in average with 98.2% selectivity) distinctly surpassing the state of the art. The key is to create a class of catalytic pocket, which contains spatially organized NH2…Cu-Se(-Zn) multiple functionalities at close range, over ZnSe colloidal quantum wells. Such structure offers a platform to mimic the concerted cooperation between the active site and surrounding secondary/outer coordination spheres in enzyme catalysis. This is manifested by the chemical adsorption and activation of CO2 via a bent geometry, favorable stabilization toward a variety of important intermediates, promotion of multielectron/proton transfer processes, etc. These results highlight the potential of incorporating enzyme-like features into the design of photocatalysts to overcome the challenges in CO2 reduction.

Delocalized Orbitals over Metal Clusters and Organic Linkers Enable Boosted Charge Transfer in Metal-Organic Framework for Overall CO2 Photoreduction

The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi-electron transfer process. Herein, taking metal-organic framework (MOF, PFC-98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC-6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge-separated (ICS) state, prolonging the excited state lifetime and further inhibiting the electron-hole recombination. The presence of ICS state prolongs the excited state lifetime and further inhibits the electron-hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi-electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.

Precisely Regulating Asymmetric Charge Distribution by Single-Atom Central Doped Ag-Based Series Clusters for Enhanced Photoreduction of CO2 to Alcohol Fuels

High efficiently photocatalytic CO2 reduction (CO2RR) into liquid fuels in pure water system remains challenged. Iron polyphthalocyanine (FePPc) with strong light harvesting, unique Fe-N4 structure, abundant pores, and good stability could serve as a promising catalyst for CO2 photoreduction. To further improve the catalytic efficiency, herein, symmetry-breaking Fe sites are constructed by coupling with atomically precise M1Ag24 (M=Ag, Au, Pt) series clusters. Especially, the introduction of Pt1Ag24 causes the most asymmetric charge distribution of Fe in FePPc (followed by Au1Ag24 and Ag25), leading to the favorable CO2 adsorption and activation. In addition, Pt1Ag24-FePPc exhibits the most effective photogenerated carriers transfer and separation. As a result, Pt1Ag24-FePPc shows the methanol/ethanol yield of 48.55/32.97 μmol ⋅ gcat -1 ⋅ h-1 in H2O-CO2 system under visible light irradiation, ~1.65/1.25-fold, 1.83/1.37-fold, and 3.60/1.61-fold higher than that of Au1Ag24-FePPc, Ag25-FePPc, and FePPc, respectively. This work provides a concept for precisely construction and regulation symmetry-breaking sites of cluster-based catalysts for effective CO2 conversion.

Strong support effect induced by MXene for the synthesis of metal sulfides nanosheet arrays with sulfur vacancies towards selective CO2-to-CO photoreduction

Selective CO2-to-CO photoreduction is under intensive research and requires photocatalysts with tuned microstructures to accelerate the reaction kinetics. Here, we report CuInS2 nanosheet arrays with sulfur vacancies (VS) grown on the two-dimensional (2D) support of Ti3C2Tx MXene for CO2-to-CO photoreduction. Our results reveal that the use of Ti3C2Tx induces strong support effect, which causes the hierarchical nanosheet arrays growth of CuInS2 and simultaneously leads to charge transfer from CuInS2 to Ti3C2Tx support, resulting in VS formed in CuInS2. The strong support effect based on Ti3C2Tx is proven to be applicable to prepare a series of different metal indium sulfide arrays with VS. CuInS2 nanosheet arrays with VS supported on Ti3C2Tx benefit the photocatalytic selective reduction of CO2 to CO, manifesting a remarkable over 14.8-fold activity enhancement compared with pure CuInS2. The experimental and computational investigations pinpoint that VS of CuInS2 resulting from the support effect of Ti3C2Tx lowers the barrier of the rate-limiting step of *COOH → *OH + *CO, which is the key to the photoactivity enhancement. This work demonstrates MXene support effects and offers an effective approach to regulate the atomic microstructure of metal sulfides toward enhancing photocatalytic performance.

Universal and scalable synthesis of photochromic single-atom catalysts for plastic recycling

Metal oxide nanostructures with single-atomic heteroatom incorporation are of interest for many applications. However, a universal and scalable synthesis approach with high heteroatom concentrations represents a formidable challenge, primarily due to the pronounced structural disparities between Mhetero-O and Msub-O units. Here, focusing on TiO2 as the exemplified substrate, we present a diethylene glycol-assisted synthetic platform tailored for the controlled preparation of a library of M1-TiO2 nanostructures, encompassing 15 distinct unary M1-TiO2 nanostructures, along with two types of binary and ternary composites. Our approach capitalizes on the unique properties of diethylene glycol, affording precise kinetic control by passivating the hydrolytic activity of heteroatom and simultaneously achieving thermodynamic control by introducing short-range order structures to dissipate the free energy associated with heteroatom incorporation. The M1-TiO2 nanostructures, characterized by distinctive and abundant M-O-Ti units on the surface, exhibit high efficiency in photochromic photothermal catalysis toward recycling waste polyesters. This universal synthetic platform contributes to the preparation of materials with broad applicability and significance across catalysis, energy conversion, and biomedicine.

Asymmetric Charge Distribution in Atomically Precise Metal Nanoclusters for Boosted CO2 Reduction Catalysis

Recently, atomically precise metal nanoclusters (NCs) have been widely applied in CO2 reduction reaction (CO2RR), achieving exciting activity and selectivity and revealing structure-performance correlation. However, at present, the efficiency of CO2RR is still unsatisfactory and cannot meet the requirements of practical applications. One of the main reasons is the difficulty in CO2 activation due to the chemical inertness of CO2. Constructing symmetry-breaking active sites is regarded as an effective strategy to promote CO2 activation by modulating electronic and geometric structure of CO2 molecule. In addition, in the subsequent CO2RR process, asymmetric charge distributed sites can break the charge balance in adjacent adsorbed C1 intermediates and suppress electrostatic repulsion between dipoles, benefiting for C-C coupling to generate C2+ products. Although compared to single atoms, metal nanoparticles, and inorganic materials the research on the construction of asymmetric catalytic sites in metal NCs is in a newly-developing stage, the precision, adjustability and diversity of metal NCs structure provide many possibilities to build asymmetric sites. This review summarizes several strategies of construction asymmetric charge distribution in metal NCs for boosting CO2RR, concludes the mechanism investigation paradigm of NCs-based catalysts, and proposes the challenges and opportunities of NCs catalysis.

Recent progress in solar-driven CO2 reduction to multicarbon products

Currently, most catalysts used for photoconverting carbon dioxide (CO2) typically produce C1 products. Achieving multicarbon (C2+) products, which are highly desirable due to their greater energy density and economic potential, still remains a significant challenge. This difficulty is primarily due to the kinetic hurdles associated with the C-C coupling step in the process. Given this, devising diverse strategies to accelerate C-C coupling for generating multicarbon products is requisite. Herein, we first give a classification of catalysts involved in the photoconversion of CO2 to C2+ fuels. We summarize metallic oxides, metallic sulfides, MXenes, and metal-organic frameworks as catalysts for CO2 photoreduction to C2+ products, attributing their efficacy to the inherent dual active sites facilitating C-C coupling. In addition, we survey covalent organic frameworks, carbon nitrides, metal phosphides, and graphene as cocatalysts for CO2 photoreduction to C2+ products, owing to the incorporated dual active sites that induce C-C coupling. In the end, we provide a brief conclusion and an outlook on designing new photocatalysts, understanding the catalytic mechanisms, and considering the practical application requirements for photoconverting CO2 into multicarbon products.

Microfluidic Continuous Synthesis of Size- and Facet-Controlled Porous Bi2O3 Nanospheres for Efficient CO2 to Formate Catalysis

Bismuth-based catalysts are effective in converting carbon dioxide into formate via electrocatalysis. Precise control of the morphology, size, and facets of bismuth-based catalysts is crucial for achieving high selectivity and activity. In this work, an efficient, large-scale continuous production strategy is developed for achieving a porous nanospheres Bi2O3-FDCA material. First-principles simulations conducted in advance indicate that the Bi2O3 (111)/(200) facets help reduce the overpotential for formate production in electrocatalytic carbon dioxide reduction reaction (ECO2RR). Subsequently, using microfluidic technology and molecular control to precisely adjust the amount of 2, 5-furandicarboxylic acid, nanomaterials rich in (111)/(200) facets are successfully synthesized. Additionally, the morphology of the porous nanospheres significantly increases the adsorption capacity and active sites for carbon dioxide. These synergistic effects allow the porous Bi2O3-FDCA nanospheres to stably operate for 90 h in a flow cell at a current density of ≈250 mA cm- 2, with an average Faradaic efficiency for formate exceeding 90%. The approach of theoretically guided microfluidic technology for the large-scale synthesis of finely structured, efficient bismuth-based materials for ECO2RR may provide valuable references for the chemical engineering of intelligent nanocatalysts.

Metal Center-Tuned Photocatalytic Carbon Dioxide Reduction for Frameworks with the Tetraphenylethene-Imidazole Ligand

As heterogeneous photocatalysts that can effectively transform CO2 to CO, two MOFs with different metal centers, namely, [M(tipe)(H2O)2](ClO4)2·solvent (M = Ni named as Ni-MOF and M = Co referred to as Co-MOF), were synthesized by reactions of 1,1,2,2-tetrakis(4-(imidazole-1-yl)phenyl)ethene (tipe) with the corresponding metal perchlorate. Both Ni-MOF and Co-MOF have 3D structures, in which the metal centers have the same coordination environment with the N4O2 donor set. Driven by visible light, the CO production catalyzed by Co-MOF is 6734.1 μmol g-1 with 45.3% selectivity, and in contrast, Ni-MOF has 4601.3 μmol g-1 CO production with 97.6% selectivity in 5 h. Through photoelectrochemical characterization, DFT calculations, and in situ FT-IR measurements, the photocatalytic CO2 reduction process catalyzed by Ni-MOF and Co-MOF was investigated. The results show that the metal center of the MOF is crucial for photocatalytic CO2 reduction. This work offers an innovative approach for controlling the performance of photocatalytic CO2 reduction through tuning the metal centers of architectures.

Regulated Photocatalytic CO2-to-CH3OH Pathway by Synergetic Dual Active Sites of Interlayer

Herein, composites of nanosheets with van der Waals contacts are employed to disclose how the interlayer-microenvironment affects the product selectivity of carbon dioxide (CO2) photoreduction. The concept of composites of nanosheets with dual active sites is introduced to manipulate the bonding configuration and promote the thermodynamic formation of methanol (CH3OH). As a prototype, the CoNi2S4-In2O3 composites of nanosheets are prepared, in which high-resolution transmission electron microscopy imaging, X-ray photoelectron spectroscopy spectra, and zeta potential tests confirm the presence of van der Waals contacts rather than chemical bonding between the In2O3 nanosheets and the CoNi2S4 nanosheets within the composite. The fabricated CoNi2S4-In2O3 composites of nanosheets exhibit the detection of the key intermediate *CH3O during CO2 photoreduction through in situ Fourier transform infrared spectra, while the In2O3 nanosheets and CoNi2S4 nanosheets alone do not show this capability, further verified by the density functional theory calculations. Accordingly, the CoNi2S4-In2O3 composites of nanosheets show the ability to produce CH3OH, whereas the CoNi2S4 and In2O3 nanosheets solely generate carbon monoxide products from CO2 photoreduction.

Pivotal Impact Factors in Photocatalytic Reduction of CO2 to Value-Added C1 and C2 Products

Over the past decades, CO2 greenhouse emission has been considerably increased, causing global warming and climate change. Indeed, converting CO2 into valuable chemicals and fuels is a desired option to resolve issues caused by its continuous emission into the atmosphere. Nevertheless, CO2 conversion has been hampered by the ultrahigh dissociation energy of C=O bonds, which makes it thermodynamically and kinetically challenging. From this prospect, photocatalytic approaches appear promising for CO2 reduction in terms of their efficiency compared to other traditional technologies. Thus, many efforts have been made in the designing of photocatalysts with asymmetric sites and oxygen vacancies, which can break the charge distribution balance of CO2 molecule, reduce hydrogenation energy barrier and accelerate CO2 conversion into chemicals and fuels. Here, we review the recent advances in CO2 hydrogenation to C1 and C2 products utilizing photocatalysis processes. We also pin down the key factors or parameters influencing the generation of C2 products during CO2 hydrogenation. In addition, the current status of CO2 reduction is summarized, projecting the future direction for CO2 conversion by photocatalysis processes.

Supported Au single atoms and nanoparticles on MoS2 for highly selective CO2-to-CH3COOH photoreduction

Effectively controlling the selective conversion of CO2 photoreduction to C2 products presents a significant challenge. Here, we develop a heterojunction photocatalyst by controllably implanting Au nanoparticles and single atoms into unsaturated Mo atoms of edge-rich MoS2, denoted as Aun/Au1-CMS. Photoreduction of CO2 results in the production of CH3COOH with a selectivity of 86.4%, which represents a 6.4-fold increase compared to samples lacking single atoms, and the overall selectivity for C2 products is 95.1%. Furthermore, the yield of CH3COOH is 22.4 times higher compared to samples containing single atoms and without nanoparticles. Optical experiments demonstrate that the single atoms domains can effectively capture photoexcited electrons by the Au nanoparticles, or the local electric field generated by the nanoparticles promotes the transfer of photogenerated electrons in MoS2 to Au single atoms, prolonging the relaxation time of photogenerated electrons. Mechanistic investigations reveal that the orbital coupling of Au5d and Mo4d strengthens the oxygen affinity of Mo and carbon affinity of Au. The hybridized orbitals reduce energy splitting levels of CO molecular orbitals, aiding C-C coupling. Moreover, the Mo-Au dual-site stabilize the crucial oxygen-associated intermediate *CH2CO, thereby enhancing the selectivity towards CH3COOH. The cross-scale heterojunctions provide an effective strategy to simultaneously address the kinetical and thermodynamical limitations of CO2-to-CH3COOH conversion.

Asymmetric Atomic Dual-Sites for Photocatalytic CO2 Reduction

Atomically dispersed active sites in a photocatalyst offer unique advantages such as locally tuned electronic structures, quantum size effects, and maximum utilization of atomic species. Among these, asymmetric atomic dual-sites are of particular interest because their asymmetric charge distribution generates a local built-in electric potential to enhance charge separation and transfer. Moreover, the dual sites provide flexibility for tuning complex multielectron and multireaction pathways, such as CO2 reduction reactions. The coordination of dual sites opens new possibilities for engineering the structure-activity-selectivity relationship. This comprehensive overview discusses efficient and sustainable photocatalysis processes in photocatalytic CO2 reduction, focusing on strategic active-site design and future challenges. It serves as a timely reference for the design and development of photocatalytic conversion processes, specifically exploring the utilization of asymmetric atomic dual-sites for complex photocatalytic conversion pathways, here exemplified by the conversion of CO2 into valuable chemicals.

Recent advances of metal active sites in photocatalytic CO2 reduction

Photocatalytic CO2 reduction captures solar energy to convert CO2 into hydrocarbon fuels, thus shifting the dependence on rapidly depleting fossil fuels. Among the various proposed photocatalysts, systems containing metal active sites (MASs) possess obvious advantages, such as effective photogenerated carrier separation, suitable adsorption and activation of intermediates, and achievable C-C coupling to generate multi-carbon (C2+) products. The present review aims to summarize the typical photocatalytic materials with MAS, highlighting the critical role of different formulations of MAS in CO2 photoreduction, especially for C2+ product generation. State-of-the-art progress in the characterization and theoretical calculations for MAS-containing photocatalysts is also emphasized. Finally, the challenges and prospects of catalytic systems involving MAS for solar-driven CO2 conversion are outlined, providing inspiration for the future design of materials for efficient photocatalytic energy conversion.

Inverted loading strategy regulates the Mn-OV-Ce sites for efficient fenton-like catalysis

Regulating interfacial active sites to improve peroxymonosulfate (PMS) activation efficiency is a hot topic in the heterogeneous catalysis field. In this study, we develop an inverted loading strategy to engineer asymmetric Mn-OV-Ce sites for PMS activation. Mn3O4@CeO2 prepared by loading CeO2 nanoparticles onto Mn3O4 nanorods exhibits the highest catalytic activity and stability, which is due to the formation of more oxygen vacancies (OV) at the Mn-OV-Ce sites, and the surface CeO2 layer effectively inhibits corrosion by preventing the loss of manganese ion active species into the solution. In situ characterizations and density functional theory (DFT) studies have revealed effective bimetallic redox cycles at asymmetric Mn-OV-Ce active sites, which promote surface charge transfer, enhance the adsorption reaction activity of active species toward pollutants, and favor PMS activation to generate (•OH, SO4•-, O2•- and 1O2) active species. This study provides a brand-new perspective for engineering the interfacial behavior of PMS activation.

Photo-to-Thermal Conversion Harnessing Low-Energy Photons Renders Efficient Solar CO2 Reduction

Efficient photocatalytic solar CO2 reduction presents a challenge because visible-to-near-infrared (NIR) low-energy photons account for over 50% of solar energy. Consequently, they are unable to instigate the high-energy reaction necessary for dissociating C═O bonds in CO2. In this study, we present a novel methodology leveraging the often-underutilized photo-to-thermal (PTT) conversion. Our unique two-dimensional (2D) carbon layer-embedded Mo2C (Mo2C-Cx) MXene catalyst in black color showcases superior near-infrared (NIR) light absorption. This enables the efficient utilization of low-energy photons via the PTT conversion mechanism, thereby dramatically enhancing the rate of CO2 photoreduction. Under concentrated sunlight, the optimal Mo2C-C0.5 catalyst achieves CO2 reduction reaction rates of 12000-15000 μmol·g-1·h-1 to CO and 1000-3200 μmol·g-1·h-1 to CH4. Notably, the catalyst delivers solar-to-carbon fuel (STF) conversion efficiencies between 0.0108% to 0.0143% and the STFavg = 0.0123%, the highest recorded values under natural sunlight conditions. This innovative approach accentuates the exploitation of low-frequency, low-energy photons for the enhancement of photocatalytic CO2 reduction.

Asymmetric Cu(I)─W Dual-Atomic Sites Enable C─C Coupling for Selective Photocatalytic CO2 Reduction to C2H4

Solar-driven CO2 reduction into value-added C2+ chemical fuels, such as C2H4, is promising in meeting the carbon-neutral future, yet the performance is usually hindered by the high energy barrier of the C─C coupling process. Here, an efficient and stabilized Cu(I) single atoms-modified W18O49 nanowires (Cu1/W18O49) photocatalyst with asymmetric Cu─W dual sites is reported for selective photocatalytic CO2 reduction to C2H4. The interconversion between W(V) and W(VI) in W18O49 ensures the stability of Cu(I) during the photocatalytic process. Under light irradiation, the optimal Cu1/W18O49 (3.6-Cu1/W18O49) catalyst exhibits concurrent high activity and selectivity toward C2H4 production, reaching a corresponding yield rate of 4.9 µmol g-1 h-1 and selectivity as high as 72.8%, respectively. Combined in situ spectroscopies and computational calculations reveal that Cu(I) single atoms stabilize the *CO intermediate, and the asymmetric Cu─W dual sites effectively reduce the energy barrier for the C─C coupling of two neighboring CO intermediates, enabling the highly selective C2H4 generation from CO2 photoreduction. This work demonstrates leveraging stabilized atomically-dispersed Cu(I) in asymmetric dual-sites for selective CO2-to-C2H4 conversion and can provide new insight into photocatalytic CO2 reduction to other targeted C2+ products through rational construction of active sites for C─C coupling.

Solar-Driven Conversion of CO2 to C2 Products by the 3d Transition Metal Intercalates of Layered Lead Iodides

Photocatalytic CO2 reduction to high-value-added C2+ products presents significant challenges, which is attributed to the slow kinetics of multi-e- CO2 photoreduction and the high thermodynamic barrier for C-C coupling. Incorporating redox-active Co2+/Ni2+ cations into lead halide photocatalysts has high potentials to improve carrier transport and introduce charge polarized bimetallic sites, addressing the kinetic and thermodynamic issues, respectively. In this study, a coordination-driven synthetic strategy is developed to introduce 3d transition metals into the interlamellar region of layered organolead iodides with atomic precision. The resultant bimetallic halide hybrids exhibit selective photoreduction of CO2 to C2H5OH using H2O vapor at the evolution rates of 24.9-31.4 µmol g-1 h-1 and high selectivity of 89.5-93.6%, while pristine layered lead iodide yields only C1 products. Band structure calculations and photoluminescence studies indicate that the interlayer Co2+/Ni2+ species greatly contribute to the frontier orbitals and enhance exciton dissociation into free carriers, facilitating carrier transport between adjacent lead iodide layers. In addition, Bader charge distribution calculations and in situ experimental spectroscopic studies reveal that the asymmetric Ni-O-Pb bimetallic catalytic sites exhibit intrinsic charge polarization, promoting C-C coupling and leading to the formation of the key *OC-CHO intermediate.

Copper Vacancy and LSPR-Activated MXene Synergistically Enabling Selective Photoreduction CO2 to Acetate

Photocatalytic CO2 conversion towards C2+ fuels is a promising technology for simultaneously achieving carbon neutrality and alleviating the energy crisis. However, this strategy is inefficient due to the difficulty of both multi-electron transfer and C-C coupling during C2+ formation. In this work, CuInS2/MXene heterostructure with Cu vacancy is rationally designed by in situ hydrothermal synthesis. The VCu-CuInS2/MXene heterostructure has a suitable band structure and tight interface contact. Catalytic performances under different testing conditions, in situ spectroscopy, and COMSOL simulation reveal that LSPR-activated MXene promotes the formation of crucial intermediate CH2* and triggers the C-C coupling process under near-infrared light, as the key to acetate. Moreover, in situ XPS analysis, DFT calculations, and photoelectrochemical characterizations unveil that copper vacancy can promote charge transfer from CuInS2 to MXene and boost local electron aggregation on the MXene, further enhancing the photocatalytic efficiency and selectivity of C2 products. Contributing to the synergistic effect of copper vacancy and plasmonic MXene, VCu-CuInS2/MXene achieved excellent CO2RR activity with an acetate evolution rate of 250.0 μmol/h/g and a selectivity of 97.5 % under the full spectrum irradiation, which is 38.8 and 3.3 times higher than that of VCu-CuInS2 and CuInS2/MXene, respectively.

Crystal Engineering of MOF-Derived Bimetallic Oxide Solid Solution Anchored with Au Nanoparticles for Photocatalytic CO2 Reduction to Syngas and C2 Hydrocarbons

Considering that CO2 reduction is mostly a multielectron reaction, it is necessary for the photocatalysts to integrate multiple catalytic sites and cooperate synergistically to achieve efficient photocatalytic CO2 reduction to various products, such as C2 hydrocarbons. Herein, through crystal engineering, we designed and constructed a metal-organic framework-derived Zr/Ti bimetallic oxide solid solution support, which was confirmed by X-ray diffraction, electron microscopy and X-ray absorption spectroscopy. After anchoring Au nanoparticles, the composite photocatalyst exhibited excellent performances toward photocatalytic CO2 reduction to syngas (H2 and CO production rates of 271.6 and 260.6 μmol g-1 h-1) and even C2 hydrocarbons (C2H4 and C2H6 production rates of 6.80 and 4.05 μmol g-1 h-1). According to the control experiments and theoretical calculations, the strong interaction between bimetallic oxide solid solution support and Au nanoparticles was found to be beneficial for binding intermediates and reducing CO2 reduction, highlighting the synergy effect of the catalytic system with multiple active sites.

Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Modulating Inorganic Dimensionality of Ultrastable Lead Halide Coordination Polymers for Photocatalytic CO2 Reduction to Ethanol

Lead halide hybrids have shown great potentials in CO2 photoreduction, but challenging to afford C2+ reduced products, especially using H2O as the reductant. This is largely due to the trade-off problem between instability of the benchmark 3D structures and low carrier mobility of quasi-2D analogues. Herein, the lead halide dimensionality of robust coordination polymers (CP) was modulated by organic ligands differing in a single-atom change (NH vs. CH2), in which the NH groups coordinate with interlamellar [PbI2] clusters to achieve the important 2D→3D transition. This first CP based on 3D cationic lead iodide sublattice possesses both high aqueous stability and a low exciton binding energy of 25 meV that is on the level of ambient thermal energy, achieving artificial photosynthesis of C2H5OH. Photophysical studies combined with theoretical calculations suggest the bridging [PbI2] clusters in the 3D structure not only results in enhanced carrier transport, but also promotes the intrinsic charge polarization to facilitate the C-C coupling. With trace loading of Rh cocatalyst, the apparent quantum efficiency of the 3D CP reaches 1.4 % at 400 nm with a high C2H5OH selectivity of 89.4 % (product basis), which presents one of the best photocatalysts for C2 products to date.

Construction of Ni/In2O3 Integrated Nanocatalysts Based on MIL-68(In) Precursors for Efficient CO2 Hydrogenation to Methanol

The efficient and economic conversion of CO2 and renewable H2 into methanol has received intensive attention due to growing concern for anthropogenic CO2 emissions, particularly from fossil fuel combustion. Herein, we have developed a novel method for preparing Ni/In2O3 nanocatalysts by using porous MIL-68(In) and nickel(II) acetylacetonate (Ni(acac)2) as the dual precursors of In2O3 and Ni components, respectively. Combined with in-depth characterization analysis, it was revealed that the utilization of MIL-68(In) as precursors favored the good distribution of Ni nanoparticles (∼6.2 nm) on the porous In2O3 support and inhibited the metal sintering at high temperatures. The varied catalyst fabrication parameters were explored, indicating that the designed Ni/In2O3 catalyst (Ni content of 5 wt %) exhibited better catalytic performance than the compared catalyst prepared using In(OH)3 as a precursor of In2O3. The obtained Ni/In2O3 catalyst also showed excellent durability in long-term tests (120 h). However, a high Ni loading (31 wt %) would result in the formation of the Ni-In alloy phase during the CO2 hydrogenation which favored CO formation with selectivity as high as 69%. This phenomenon is more obvious if Ni and In2O3 had a strong interaction, depending on the catalyst fabrication methods. In addition, with the aid of in situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory (DFT) calculations, the Ni/In2O3 catalyst predominantly follows the formate pathway in the CO2 hydrogenation to methanol, with HCOO* and *H3CO as the major intermediates, while the small size of Ni particles is beneficial to the formation of formate species based on DFT calculation. This study suggests that the Ni/In2O3 nanocatalyst fabricated using metal-organic frameworks as precursors can effectively promote CO2 thermal hydrogenation to methanol.

CO2 Enrichment Boosts Highly Selective Infrared-Light-Driven CO2 Conversion to CH4 by UiO-66/Co9S8 Photocatalyst

Photocatalytic CO2 reduction to high-value chemicals is an attractive approach to mitigate climate change, but it remains a great challenge to produce a specific product selectively by IR light. Hence, UiO-66/Co9S8 composite is designed to couple the advantages of metallic photocatalysts and porous CO2 adsorbers for IR-light-driven CO2-to-CH4 conversion. The metallic nature of Co9S8 endows UiO-66/Co9S8 with exceptional IR light absorption, while UiO-66 dramatically enhances its local CO2 concentration, revealed by finite-element method simulations. As a result, Co9S8 or UiO-66 alone does not show observable IR-light photocatalytic activity, whereas UiO-66/Co9S8 exhibits exceptional activity. The CH4 evolution rate over UiO-66/Co9S8 reaches 25.7 µmol g-1 h-1 with ca.100% selectivity under IR light irradiation, outperforming most reported catalysts under similar reaction conditions. The X-ray absorption fine structure spectroscopy spectra verify the presence of two distinct Co sites and confirm the existence of metallic Co─Co bond in Co9S8. Energy diagrams analysis and transient absorption spectra manifest that CO2 reduction mainly occurs on Co9S8 for UiO-66/Co9S8, while density functional theory calculations demonstrate that high-electron-density Co1 sites are the key active sites, possessing lower energy barriers for further protonation of *CO, leading to the ultra-high selectivity toward CH4.

Light-Driven C-C Coupling for Targeted Synthesis of CH3 COOH with Nearly 100 % Selectivity from CO2

Targeted synthesis of acetic acid (CH3 COOH) from CO2 photoreduction under mild conditions mainly limits by the kinetic challenge of the C-C coupling. Herein, we utilized doping engineering to build charge-asymmetrical metal pair sites for boosted C-C coupling, enhancing the activity and selectivity of CO2 photoreduction towards CH3 COOH. As a prototype, the Pd doped Co3 O4 atomic layers are synthesized, where the established charge-asymmetrical cobalt pair sites are verified by X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy spectra. Theoretical calculations not only reveal the charge-asymmetrical cobalt pair sites caused by Pd atom doping, but also manifest the promoted C-C coupling of double *COOH intermediates through shortening of the coupled C-C bond distance from 1.54 to 1.52 Å and lowering their formation energy barrier from 0.77 to 0.33 eV. Importantly, the decreased reaction energy barrier from the protonation of two*COOH into *CO intermediates for the Pd-Co3 O4 atomic layer slab is 0.49 eV, higher than that of the Co3 O4 atomic layer slab (0.41 eV). Therefore, the Pd-Co3 O4 atomic layers exhibit the CH3 COOH evolution rate of ca. 13.8 μmol g-1  h-1 with near 100% selectivity, both of which outperform all previously reported single photocatalysts for CO2 photoreduction towards CH3 COOH under similar conditions.

Efficient Alkene Hydroformylation by Co-C Symmetry-Breaking Sites

Alkene hydroformylation is one of the largest industrial reactions on an industrial scale; however, the development of nonnoble heterogeneous catalysts is usually limited by their low activities and stabilities. Herein, we constructed a 1% Co2C/SiO2 catalyst featuring Co-Cvacancy-Co-C symmetry-breaking sites, which generated a polar surface exhibiting a moderate charge density gradient at the localized Co atoms. Comparatively, this catalyst exhibited notable enhancements in the adsorption and activation of the reactants, as well as in the polarity between intermediates. Significantly, the spatial distance between the adsorption sites of intermediates was reduced, thereby effectively decreasing the energy barrier of reaction processes. As the density of the symmetry-breaking sites increased, the turnover number for propene hydroformylation soared to 18 363, exceeding the activity of heterogeneous Co-based catalysts reported thus far by 1 or 2 orders of magnitude, and the catalyst exhibited high stability during the reaction. This study provides a methodology for constructing atomically active sites, which holds great potential for the design and development of highly efficient catalysts.

Light-driven thermocatalytic CO2 reduction by CH4 on alumina-cluster-modified Ni nanoparticles with excellent durability and high light-to-fuel efficiency promoted by the photoactivation effect

Using inexhaustible solar energy to drive efficient light-driven thermocatalytic CO2 reduction by CH4 (DRM) is an attractive approach that can synchronously reduce the greenhouse effect and convert solar energy into fuels. However, it is often limited by the intense light intensity required to produce high fuel production rates, and the catalyst deactivation due to severe carbon deposition generated from side reactions. Herein, a nanostructure of alumina-cluster-modified Ni nanoparticles supported on Al2O3 nanorods (ACM-Ni/Al2O3) was synthesized, displaying good catalytic performance under focused UV-vis-IR illumination. By light-driven thermocatalytic DRM on ACM-Ni/Al2O3 at a reduced light intensity of 76.9 kW m-2, the high fuel production rates of H2 (rH2, 65.7 mmol g-1 min-1) and CO (rCO, 78.8 mmol g-1 min-1), as well as an efficient light-to-fuel efficiency (η, 26.3 %) are achieved without additional heating. The rH2 and rCO of light-driven thermocatalysis are 2.9 and 1.9 times higher, respectively, compared to conventional thermocatalysis at the same temperature. We have discovered that high light-driven thermocatalytic activity originates from the photoactivation effect, significantly reducing the apparent activation energy and facilitating C* oxidation as a decisive step in DRM. ACM-Ni/Al2O3 possesses excellent durability and exhibits an extremely low coking rate of 4.40 × 10-3 gc gcatalyst-1 h-1, which is 26.8 times lower than that of the reference sample without Al2O3 cluster modification (R-Ni/Al2O3). This is owing to a decrease in activation energies (Ea) of C* oxidation and an increase in Ea of C* polymerization by the surface modification of Ni nanoparticles with Al2O3 clusters, effectively inhibiting carbon deposition.

Guiding the Driving Factors on Plasma Super-Photothermal S-Scheme Core-Shell Nanoreactor to Enhance Photothermal Catalytic H2 Evolution and Selective CO2 Reduction

Light-induced heat has a non-negligible role in photocatalytic reactions. However, it is still challenging to design highly efficient catalysts that can make use of light and thermal energy synergistically. Herein, the study proposes a plasma super-photothermal S-scheme heterojunction core-shell nanoreactor based on manipulation of the driving factors, which consists of α-Fe2 O3 encapsulated by g-C3 N4 modified with gold quantum dots. α-Fe2 O3 can promote carrier spatial separation while also acting as a thermal core to radiate heat to the shell, while Au quantum dots transfer energetic electrons and heat to g-C3 N4 via surface plasmon resonance. Consequently, the catalytic activity of Au/α-Fe2 O3 @g-C3 N4 is significantly improved by internal and external double hot spots, and it shows an H2 evolution rate of 5762.35 µmol h-1 g-1 , and the selectivity of CO2 conversion to CH4 is 91.2%. This work provides an effective strategy to design new plasma photothermal catalysts for the solar-to-fuel transition.

Water-Mediated Selectivity Control of CH3 OH versus CO/CH4 in CO2 Photoreduction on Single-Atom Implanted Nanotube Arrays

Controllable methanol production in artificial photosynthesis is highly desirable due to its high energy density and ease of storage. Herein, single atom Fe is implanted into TiO2 /SrTiO3 (TSr) nanotube arrays by two-step anodization and Sr-induced crystallization. The resulting Fe-TSr with both single Fe reduction centers and dominant oxidation facets (001) contributes to efficient CO2 photoreduction and water oxidation for controlled production of CH3 OH and CO/CH4 . The methanol yield can reach to 154.20 µmol gcat -1 h-1 with 98.90% selectivity by immersing all the catalyst in pure water, and the yield of CO/CH4 is 147.48 µmol gcat -1 h-1 with >99.99% selectivity when the catalyst completely outside water. This CH3 OH yield is 50 and 3 times higher than that of TiO2 and TSr and stands among all the state-of-the-art catalysts. The facile gas-solid and gas-liquid-solid phase switch can selectively control CH3 OH production from ≈0% (above H2 O) to 98.90% (in H2 O) via slowly immersing the catalyst into water, where abundant •OH and H2 O around Fe sites play important role in selective CH3 OH production. This work highlights a new insight for water-mediated CO2 photoreduction to controllably produce CH3 OH.

Tandem Synergistic Effect of Cu-In Dual Sites Confined on the Edge of Monolayer CuInP2 S6 toward Selective Photoreduction of CO2 into Multi-Carbon Solar Fuels

One-unit-cell, single-crystal, hexagonal CuInP2 S6 atomically thin sheets of≈0.81 nm in thickness was successfully synthesized for photocatalytic reduction of CO2 . Exciting ethene (C2 H4 ) as the main product was dominantly generated with the yield-based selectivity reaching ≈56.4 %, and the electron-based selectivity as high as ≈74.6 %. The tandem synergistic effect of charge-enriched Cu-In dual sites confined on the lateral edge of the CuInP2 S6 monolayer (ML) is mainly responsible for efficient conversion and high selectivity of the C2 H4 product as the basal surface site of the ML, exposing S atoms, can not derive the CO2 photoreduction due to the high energy barrier for the proton-coupled electron transfer of CO2 into *COOH. The marginal In site of the ML preeminently targets CO2 conversion to *CO under light illumination, and the *CO then migrates to the neighbor Cu sites for the subsequent C-C coupling reaction into C2 H4 with thermodynamic and kinetic feasibility. Moreover, ultrathin structure of the ML also allows to shorten the transfer distance of charge carriers from the interior onto the surface, thus inhibiting electron-hole recombination and enabling more electrons to survive and accumulate on the exposed active sites for CO2 reduction.

Selective Photoreduction of CO2 to CH4 Triggered by Metal-Vacancy Pair Sites

Selectively achieving the photoreduction of carbon dioxide (CO2) to methane (CH4) remains a significant challenge, which primarily arises from the complexity of the protonation process. In this work, we designed metal-vacancy pair sites in defective metal oxide semiconductors, which anchor the reactive intermediates with a bridged linkage for the selective protonation to produce CH4. As an example, oxygen-deficient Nb2O5 nanosheets are synthesized, in which the niobium-oxygen vacancy pair sites are demonstrated by X-ray photoelectron spectroscopy and electron paramagnetic resonance spectra. In situ Fourier transform infrared spectroscopy monitors the *CH3O intermediate, a key intermediate for CH4 production, during the CO2 photoreduction in oxygen-deficient Nb2O5 nanosheets. Importantly, the built metal-vacancy pair sites regulate the *CH3O formation step as a spontaneous process, making the reduction of CO2 to CH4 the preferred method. Therefore, the oxygen-deficient Nb2O5 nanosheets exhibit a CH4 formation rate of 19.14 μmol g-1 h-1, with an electron selectivity of ∼94.1%.

Embedded Mo/Mn Atomic Regulation for Durable Acidity-Reinforced HZSM-5 Catalyst toward Energy-Efficient Amine Regeneration

Metal-molecular sieve composites with high acidity are promising solid acid catalysts (SACs) for accelerating sluggish CO2 desorption processes and reducing the energy consumption of CO2 chemisorption systems. However, the production of such SACs through conventional approaches such as loading or ion-exchange methods often leads to uncontrolled and unstable metal distribution on the catalysts, which limits their pore structure regulation and catalytic performance. In this study, we demonstrated a feasible strategy for improving the durability, surface chemical activity, and pore structure of metal-doped HZSM-5 through bimetallic Mo/Mn modification. This strategy involves the immobilization of Mo-O-Mn species confined in an MFI structure by regulating MoO42- anions and Mn2+ cations. The embedded Mn/Mo species of low valence can strongly induce electron transfer and increase the density of compensatory H+ on the MoMn@H catalyst, thereby reducing the CO2 desorption temperature by 8.27 °C and energy consumption by 37% in comparison to a blank. The durability enhancement and activity regulation method used in this study is expected to advance the rational synthesis of metal-molecular sieve composites for energy-efficient CO2 capture using amine regeneration technology.

Metal to non-metal sites of metallic sulfides switching products from CO to CH4 for photocatalytic CO2 reduction

The active center for the adsorption and activation of carbon dioxide plays a vital role in the conversion and product selectivity of photocatalytic CO2 reduction. Here, we find multiple metal sulfides CuInSnS4 octahedral nanocrystal with exposed (1 1 1) plane for the selectively photocatalytic CO2 reduction to methane. Still, the product is switched to carbon monoxide on the corresponding individual metal sulfides In2S3, SnS2, and Cu2S. Unlike the common metal or defects as active sites, the non-metal sulfur atom in CuInSnS4 is revealed to be the adsorption center for responding to the selectivity of CH4 products. The carbon atom of CO2 adsorbed on the electron-poor sulfur atom of CuInSnS4 is favorable for stabilizing the intermediates and thus promotes the conversion of CO2 to CH4. Both the activity and selectivity of CH4 products over the pristine CuInSnS4 nanocrystal can be further improved by the modification of with various co-catalysts to enhance the separation of the photogenerated charge carrier. This work provides a non-metal active site to determine the conversion and selectivity of photocatalytic CO2 reduction.

Enhanced acetate utilization for value-added chemicals production in Yarrowia lipolytica by integration of metabolic engineering and microbial electrosynthesis

The limited supply of reducing power restricts the efficient utilization of acetate in Yarrowia lipolytica. Here, microbial electrosynthesis (MES) system, enabling direct conversion of inward electrons to NAD(P)H, was used to improve the production of fatty alcohols from acetate based on pathway engineering. First, the conversion efficiency of acetate to acetyl-CoA was reinforced by heterogenous expression of ackA-pta genes. Second, a small amount of glucose was used as cosubstrate to activate the pentose phosphate pathway and promote intracellular reducing cofactors synthesis. Third, through the employment of MES system, the final fatty alcohols production of the engineered strain YLFL-11 reached 83.8 mg/g dry cell weight (DCW), which was 6.17-fold higher than the initial production of YLFL-2 in shake flask. Furthermore, these strategies were also applied for the elevation of lupeol and betulinic acid synthesis from acetate in Y. lipolytica, demonstrating that our work provides a practical solution for cofactor supply and the assimilation of inferior carbon sources.

Dual Lewis Acid-Base Sites Regulate Silver-Copper Bimetallic Oxide Nanowires for Highly Selective Photoreduction of Carbon Dioxide to Methane

Highly selective photoreduction of CO2 to valuable hydrocarbons is of great importance to achieving a carbon-neutral society. Precisely manipulating the formation of the Metal1 ⋅⋅⋅C=O⋅⋅⋅Metal2 (M1 ⋅⋅⋅C=O⋅⋅⋅M2 ) intermediate on the photocatalyst interface is the most critical step for regulating selectivity, while still a significant challenge. Herein, inspired by the polar electronic structure feature of CO2 molecule, we propose a strategy whereby the Lewis acid-base dual sites confined in a bimetallic catalyst surface are conducive to forming a M1 ⋅⋅⋅C=O⋅⋅⋅M2 intermediate precisely, which can promote selectivity to hydrocarbon formation. Employing the Ag2 Cu2 O3 nanowires with abundant Cu⋅⋅⋅Ag Lewis acid-base dual sites on the preferred exposed {110} surface as a model catalyst, 100 % selectivity toward photoreduction of CO2 into CH4 has been achieved. Subsequent surface-quenching experiments and density functional theory (DFT) calculations verify that the Cu⋅⋅⋅Ag Lewis acid-base dual sites do play a vital role in regulating the M1 ⋅⋅⋅C=O⋅⋅⋅M2 intermediate formation that is considered to be prone to convert CO2 into hydrocarbons. This study reports a highly selective CO2 photocatalyst, which was designed on the basis of a newly proposed theory for precise regulation of reaction intermediates. Our findings will stimulate further research on dual-site catalyst design for CO2 reduction to hydrocarbons.

Fundamentals and Challenges of Engineering Charge Polarized Active Sites for CO2 Photoreduction toward C2 Products

ConspectusGlobal warming and climatic deterioration are partly caused by carbon dioxide (CO2) emission. Given this, CO2 reduction into valuable carbonaceous fuels is a win-win route to simultaneously alleviate the greenhouse effect and the energy crisis, where CO2 reduction into hydrocarbon fuels by solar energy may be a potential strategy. Up to now, most of the current photocatalysts photoconvert CO2 to C1 products. It is extremely difficult to achieve production of C2 products, which have higher economic value and energy density, due to the kinetic challenge of C-C coupling of the C1 intermediates. Therefore, to realize CO2 photoreduction to C2 fuels, design of high-activity photocatalysts to expedite the C-C coupling is significant. Besides, the current mechanism for CO2 photoreduction toward C2 fuels is usually uncertain, which is possibly attributed to the following two reasons: (1) It is arduous to determine the actual catalytic sites for the C-C coupling step. (2) It is hard to monitor the low-concentration active intermediates during the multielectron transfer step.Most traditional metal-based photocatalysts usually possess charge balanced active sites that have the same charge density. In this aspect, the neighboring C1 intermediates may also show the same charge distribution, which would lead to dipole-dipole repulsion, thus preventing C-C coupling for producing C2 fuels. By contrast, photocatalysts with charge polarized active sites possess obviously different charge distributions in the adjacent C1 intermediates, which can effectively suppress the electrostatic repulsion to steer the C-C coupling. Based on this analysis, higher asymmetric charge density on the active sites would be more beneficial to anchoring between the adjacent intermediates and active atoms in catalysts, which can boost C-C coupling.In this Account, we summarize various strategies, including vacancy engineering, doping engineering, loading engineering, and heterojunction engineering, for tailoring charge polarized active sites to boost the C-C coupling for the first time. Also, we overview diverse in situ characterization technologies, such as in situ X-ray photoelectron spectroscopy, in situ Raman spectroscopy, and in situ Fourier transform infrared spectroscopy, for determining charge polarized active sites and monitoring reaction intermediates, helping to reveal the internal catalytic mechanism of CO2 photoreduction toward C2 products. We hope this Account may help readers to understand the crucial function of charge polarized active sites during CO2 photoreduction toward C2 products and provide guidance for designing and preparing highly active catalysts for photocatalytic CO2 reduction.

A dual Z-scheme heterojunction Cu-CuTCPP/Cu2O/CoAl-LDH for photocatalytic CO2 reduction to C1 and C2 products

In this research, a ternary Cu-CuTCPP/Cu2O/CoAl-LDH composite with a dual Z-scheme heterostructure was fabricated based on a Cu2O photocatalyst and applied in photocatalytic CO2 reduction. The physicochemical properties of the prepared catalysts and the possible reaction mechanism in CO2 reduction were analyzed and studied by various characterization methods. The activity of CO2 reduction significantly increased, especially forming C2 products. The optimal yield of C2H4 and C2H6 reached 1.56 and 1.92 μmol g-1 h-1 respectively, which was 14.45 and 17.45 times that from using the Cu2O monomer. In addition, the selectivity of C2 products reached 37.4%. The satisfactory C2 yield was mainly due to the fact that Cu1+δ2(COO)3 nodes in Cu-CuTCPP contained adjacent Cu sites, which effectively promoted the C-C coupling reaction. Moreover, the dual Z-scheme heterojunction stimulated the separation of photogenerated electron-hole pairs and diminished the recombination rate. This work contributes to the development of novel photocatalysts with a dual Z-scheme heterojunction and facilitates the generation of valuable C2 products.

Research Progress on Photocatalytic CO2 Reduction Based on Perovskite Oxides

Photocatalytic CO2 reduction to valuable fuels is a promising way to alleviate anthropogenic CO2 emissions and energy crises. Perovskite oxides have attracted widespread attention as photocatalysts for CO2 reduction by virtue of their high catalytic activity, compositional flexibility, bandgap adjustability, and good stability. In this review, the basic theory of photocatalysis and the mechanism of CO2 reduction over perovskite oxide are first introduced. Then, perovskite oxides' structures, properties, and preparations are presented. In detail, the research progress on perovskite oxides for photocatalytic CO2 reduction is discussed from five aspects: as a photocatalyst in its own right, metal cation doping at A and B sites of perovskite oxides, anion doping at O sites of perovskite oxides and oxygen vacancies, loading cocatalyst on perovskite oxides, and constructing heterojunction with other semiconductors. Finally, the development prospects of perovskite oxides for photocatalytic CO2 reduction are put forward. This article should serve as a useful guide for creating perovskite oxide-based photocatalysts that are more effective and reasonable.

Size Effects of Highly Dispersed Bismuth Nanoparticles on Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

Electrocatalytic reduction of carbon dioxide into value-added chemical fuels is a promising way to achieve carbon neutrality. Bismuth-based materials have been considered as favorable electrocatalysts for converting carbon dioxide to formic acid. Moreover, size-dependent catalysis offers significant advantages in catalyzed heterogeneous chemical processes. However, the size effects of bismuth nanoparticles on formic acid production have not been fully explored. Here, we prepared Bi nanoparticles uniformly supported on porous TiO₂ substrate electrocatalytic materials by in situ segregation of the Bi element from Bi₄Ti₃O₁₂. The Bi-TiO₂ electrocatalyst with Bi nanoparticles of 2.83 nm displays a Faradaic efficiency of greater than 90% over a wide potential range of 400 mV. Theoretical calculations have also demonstrated subtle electronic structural evolutions induced by the size variations of Bi nanoparticles, where the 2.83 nm Bi nanoparticles display the most active p-band and d-band centers to guarantee high electroactivity toward CO₂RR.

Super-Photothermal Effect-Mediated Fast Reaction Kinetic in S-Scheme Organic/Inorganic Heterojunction Hollow Spheres Toward Optimized Photocatalytic Performance

Using full solar spectrum for energy conversion and environmental remediation is a major challenge, and solar-driven photothermal chemistry is a promising route to achieve this goal. Herein, this work reports a photothermal nano-constrained reactor based on hollow structured g-C₃ N₄ @ZnIn₂ S₄ core-shell S-scheme heterojunction, where the synergistic effect of super-photothermal effect and S-scheme heterostructure significantly improve the photocatalytic performance of g-C₃ N₄ . The formation mechanism of g-C₃ N₄ @ZnIn₂ S₄ is predicted in advance by theoretical calculations and advanced techniques, and the super-photothermal effect of g-C₃ N₄ @ZnIn₂ S₄ and its contribution to the near-field chemical reaction is confirmed by numerical simulations and infrared thermography. Consequently, the photocatalytic degradation rate of g-C₃ N₄ @ZnIn₂ S₄ for tetracycline hydrochloride is 99.3%, and the photocatalytic hydrogen production is up to 4075.65 µmol h^-1 g^-1 , which are 6.94 and 30.87 times those of pure g-C₃ N₄ , respectively. The combination of S-scheme heterojunction and thermal synergism provides a promising insight for the design of an efficient photocatalytic reaction platform.

Exfoliation of a Two-Dimensional Metal-Organic Framework for Enhanced Photocatalytic CO2 Reduction

A two-dimensional metal-organic framework, FICN-12, was constructed from tris[4-(1H-pyrazole-4-yl)phenyl]amine (H₃TPPA) ligands and Ni₂ secondary building units. The triphenylamine moiety in the H₃TPPA ligand readily absorbs UV-visible photons and sensitizes the Ni center to drive photocatalytic CO₂ reduction. FICN-12 can be exfoliated into monolayer and few-layer nanosheets with a "top-down" approach, which exposes more catalytic sites and increases its catalytic activity. As a result, the nanosheets (FICN-12-MONs) showed photocatalytic CO and CH₄ production rates of 121.15 and 12.17 μmol/g/h, respectively, nearly 1.4 times higher than those of bulk FICN-12.

Recent Advances in Carbon Nitride-Based S-scheme Photocatalysts for Solar Energy Conversion

Energy shortages are a major challenge to the sustainable development of human society, and photocatalytic solar energy conversion is a potential way to alleviate energy problems. As a two-dimensional organic polymer semiconductor, carbon nitride is considered to be the most promising photocatalyst due to its stable properties, low cost, and suitable band structure. Unfortunately, pristine carbon nitride has low spectral utilization, easy recombination of electron holes, and insufficient hole oxidation ability. The S-scheme strategy has developed in recent years, providing a new perspective for effectively solving the above problems of carbon nitride. Therefore, this review summarizes the latest progress in enhancing the photocatalytic performance of carbon nitride via the S-scheme strategy, including the design principles, preparation methods, characterization techniques, and photocatalytic mechanisms of the carbon nitride-based S-scheme photocatalyst. In addition, the latest research progress of the S-scheme strategy based on carbon nitride in photocatalytic H₂ evolution and CO₂ reduction is also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced nitride-based S-scheme photocatalysts are presented. This review brings the research of carbon nitride-based S-scheme strategy to the forefront and is expected to guide the development of the next-generation carbon nitride-based S-scheme photocatalysts for efficient energy conversion.