Accelerated Photocatalytic Carbon Dioxide Reduction and Water Oxidation under Spatial Synergy.

Photocatalytic conversion of CO2 and H2 O into fuels and oxygen is a highly promising solution for carbon-neutral recycling. Traditionally, researchers have studied CO2 reduction and H2 O oxidation separately, overlooking potential synergistic interplay between these processes. This study introduces an innovative approach, spatial synergy, which encourages synergistic progress by bringing the two half-reactions into atomic proximity. To facilitate this, we developed a defective ZnIn2 S4 -supported single-atom Cu catalyst (Cu-SA/D-ZIS), which demonstrates remarkable catalytic performance with CO2 reduction rates of 112.5 µmol g-1 h-1 and water oxidation rates of 52.3 µmol g-1 h-1 , exhibiting a six-fold enhancement over D-ZIS. The structural characterization results indicated that the trapping effect of vacancy associates on single-atom copper led to the formation of an unsaturated coordination structure, Cu-S3 , consequently giving rise to the CuZn 'VS ⋅⋅VZn " defect complexes. FT-IR studies coupled with theoretical calculations reveal the spatially synergistic CO2 reduction and water oxidation on CuZn 'VS ⋅⋅VZn ", where the breakage of O-H in water oxidation is synchronized with the formation of *COOH, significantly lowering the energy barrier. Notably, this study introduces and, for the first time, substantiates the spatial synergy effect in CO2 reduction and H2 O oxidation through a combination of experimental and theoretical analyses, providing a fresh insight in optimizing photocatalytic system.

Fe-N Co-Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation.

Bismuth vanadate ranks among the most promising photoanodes for photoelectrochemical water splitting. Nonetheless, slow charge separation and transport are key barriers to its photoefficiency. Here, we present a co-doping strategy that significantly improves the charge separation performance of BVO. Under standard one sun illumination, the Fe-N co-doped BVO photoanode (Fe-N-BVO) by N-coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm-2 at 1.23 V vs RHE after modified a surface co-catalyst. By contrast, much lower photocurrent density is obtained for the N-doped and Fe-doped BVO with separated N and Fe precursors. The detailed characterizations show that the high activity of the Fe-N-BVO is attributed to the enhanced photo-induced bulk charge separation and the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co-doping of Fe-N into BVO generates Fe-based electronic states just below the bottom of conduction band and N-derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo-induced carriers, but hinder the charge recombination originated from the deep trapping sites.

Strong Spin Polarization Effect of Atomically Dispersed Metal Site Boosts the Selective Photocatalytic Nitrobenzene Hydrogenation to Aniline over Graphitic Carbon Nitride.

Atomically dispersed catalysts (ADCs) with a well-defined structure are theoretically desirable for a high-selectivity photocatalytic reaction. However, achieving high product selectivity remains a practical challenge for ADCs-based photocatalysts. Herein, we reveal a spin polarization effect on achieving high product selectivity (95.0%) toward the photocatalytic nitrobenzene (PhNO2) hydrogenation to aniline (PhNH2) on atomically dispersed Fe site-loaded graphitic carbon nitride (Fe/g-C3N4). In combination with the Gibbs free energy diagram and electronic structure analysis, the origin of the photocatalytic performance is attributed not only to the strong metal-support interaction between the Fe site and g-C3N4, but more importantly to the strong spin polarization effect that promotes the potential-determining step (PDS) of *PhNO to *PhNOH. This work could be helpful for the design of ADCs-based photocatalysts in view of the spin polarization effect.

Facilitated Photocatalytic CO2 Reduction in Aerobic Environment on a Copper-Porphyrin Metal-Organic Framework.

Herein, we fabricated a π-π stacking hybrid photocatalyst by combining two two-dimensional (2D) materials: g-C3 N4 and a Cu-porphyrin metal-organic framework (MOF). After an aerobic photocatalytic pretreatment, this hybrid catalyst exhibited an unprecedented ability to photocatalytically reduce CO2 to CO and CH4 under the typical level (20 %) of O2 in the air. Intriguingly, the presence of O2 did not suppress CO2 reduction; instead, a fivefold increase compared with that in the absence of O2 was observed. Structural analysis indicated that during aerobic pretreatment, the Cu node in the 2D-MOF moiety was hydroxylated by the hydroxyl generated from the reduction of O2 . Then the formed hydroxylated Cu node maintained its structure during aerobic CO2 reduction, whereas it underwent structural alteration and was reductively devitalized in the absence of O2 . Theoretical calculations further demonstrated that CO2 reduction, instead of O2 reduction, occurred preferentially on the hydroxylated Cu node.

In Situ Observation of Hot Carrier Transfer at Plasmonic Au/Metal-Organic Frameworks (MOFs) Interfaces.

Constructing heterostructures have been demonstrated as an ideal strategy for boosting charge separation on plasmonic photocatalysts, but the detailed interface charge transfer mechanism remains elusive. Herein, that authors fabricate plasmonic Au and metal-organic frameworks (MOFs, NH2 -MIL-125 and MIL-125 used in this work) heterostructures and explore the interface charge transfer mechanism by in situ electron paramagnetic resonance (EPR) spectroscopy and electrochemical measurements. The plasmon-excited hot electrons on Au can transfer across the Au/MOF interface and be captured by the coordinatively unsaturated sites of secondary building units (Ti8 O8 (OH)4 cluster) of the MOF structure, and the plasmon-excited hot holes on Au tend to transfer to and be trapped at the functionalized organic ligand (1,4-benzenedicarboxylate-NH2 ). The spatially separated hot electrons and holes exhibit boosted the photocatalytic activity for chromium (VI) reduction and selective benzyl alcohol oxidation. This work illustrates the advantage of the versatile functionalization of MOF structures enabling molecular-level manipulation of interface charge transfer on plasmonic photocatalysts.

Photocatalytic C-C Coupling from Carbon Dioxide Reduction on Copper Oxide with Mixed-Valence Copper(I)/Copper(II).

To realize the evolution of C2+ hydrocarbons like C2H4 from CO2 reduction in photocatalytic systems remains a great challenge, owing to the gap between the relatively lower efficiency of multielectron transfer in photocatalysis and the sluggish kinetics of C-C coupling. Herein, with Cu-doped zeolitic imidazolate framework-8 (ZIF-8) as a precursor, a hybrid photocatalyst (CuOX@p-ZnO) with CuOX uniformly dispersed among polycrystalline ZnO was synthesized. Upon illumination, the catalyst exhibited the ability to reduce CO2 to C2H4 with a 32.9% selectivity, and the evolution rate was 2.7 µmol·g-1·h-1 with water as a hole scavenger and as high as 22.3 µmol·g-1·h-1 in the presence of triethylamine as a sacrificial agent, all of which have rarely been achieved in photocatalytic systems. The X-ray absorption fine structure spectra coupled with in situ FT-IR studies reveal that, in the original catalyst, Cu mainly existed in the form of CuO, while a unique Cu+ surface layer upon the CuO matrix was formed during the photocatalytic reaction, and this surface Cu+ site is the active site to anchor the in situ generated CO and further perform C-C coupling to form C2H4. The C-C coupling intermediate *OC-COH was experimentally identified by in situ FT-IR studies for the first time during photocatalytic CO2 reduction. Moreover, theoretical calculations further showed the critical role of such Cu+ sites in strengthening the binding of *CO and stabilizing the C-C coupling intermediate. This work uncovers a new paradigm to achieve the reduction of CO2 to C2+ hydrocarbons in a photocatalytic system.

Achieving Almost 100% Selectivity in Photocatalytic CO2 Reduction to Methane via In-Situ Atmosphere Regulation Strategy.

Artificial photosynthesis, harnessing solar energy to convert CO2 into hydrocarbons, presents a promising solution for climate change and energy scarcity. However, photocatalytic CO2 reduction often terminates at the CO stage due to limited electron transfer capacity, hindering the formation of higher-energy hydrocarbons such as CH4. This study introduces, for the first time, an in-situ atmosphere regulation strategy, refined from molecular imprinting methodologies, using dynamically reacting molecules to precisely engineer photocatalytic surface sites for selective *CO adsorption and hydrogenation in CO2-to-CH4 conversion. Specifically, the single-atom Cu catalyst (Cu-SA-CO) is prepared by anchoring single-atom Cu onto defective TiO2 substrates (Cu-SA-CO) under a CO reduction atmosphere. Under illumination, the catalyst exhibited outstanding CH4 selectivity (almost 100%) and productivity (58.5 µmol g-1 h-1). Mechanistic investigations reveal that the coordination environment of the Cu single atoms is significantly affected by dynamically reacting molecules (CO and *CHxO) during synthesis, leading to a Ti-Cu-O structure. The structure, with the synergistic interaction between Cu single atoms and oxygen defects, significantly enhances *CO adsorption and hydrogenation, thereby promoting the formation of methane. This work pioneers the use of dynamically reactive molecules as imprinted templates to tune photocatalytic CO2 reduction selectivity, providing a novel avenue for designing efficient photocatalysts.

Boosting the Faradaic Efficiency of Br--Mediated Photoelectrochemical Epoxidation by Local Acidity on α-Fe2O3.

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value-added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br-/HOBr-mediated method is developed to achieve a near-quantitative selectivity and ≈100% FE of styrene oxide on α-Fe2O3, in which low concentration of Br- as mediator and locally generated acidic micro-environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH-dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications.

Aligning Metal Coordination Sites in Metal-Organic Framework-Enabled Metallaphotoredox Catalysis.

Construction of catalytic metal centers, the key modules in artificial photosynthetic systems, lies at the heart to explore unpaved reactivity patterns powered by light. Here, we disclose that the amino (-NH2) and carboxylic (-COO) functionalities, aligned in various visible-light-harvesting metal-organic frameworks (MOFs) (NH2-UiO-66, (NH2)2-UiO-67, and NH2-MIL-125), provide N/O-ligated Ni featuring different configurations and valence states. Of note, these Ni centers, in situ formed or preimplanted, demonstrated coordination units' spatial arrangement-dependent activity in cross-coupling of aryl halides and various nucleophiles. Our work provides a novel approach to construct and to regulate metal center(s) by MOFs' skeleton defined coordination environments, highlighting exclusive potential in exploring the reactivity pattern of the hosted metals.

Br-/BrO--mediated highly efficient photoelectrochemical epoxidation of alkenes on α-Fe2O3.

Epoxides are significant intermediates for the manufacture of pharmaceuticals and epoxy resins. In this study, we develop a Br-/BrO- mediated photoelectrochemical epoxidation system on α-Fe2O3. High selectivity (up to >99%) and faradaic efficiency (up to 82 ± 4%) for the epoxidation of a wide range of alkenes are achieved, with water as oxygen source, which are far beyond the most reported electrochemical and photoelectrochemical epoxidation performances. Further, we can verify that the epoxidation reaction is mediated by Br-/BrO- route, in which Br- is oxidized non-radically to BrO- by an oxygen atom transfer pathway on α-Fe2O3, and the formed BrO- in turn transfers its oxygen atom to the alkenes. The non-radical mediated characteristic and the favorable thermodynamics of the oxygen atom transfer process make the epoxidation reactions very efficient. We believe that this photoelectrochemical Br-/BrO--mediated epoxidation provides a promising strategy for value-added production of epoxides and hydrogen.