Photoredox-Promoted Co-Production of Dihydroisoquinoline and H2 O2 over Defective Zn3 In2 S6

Sacrificial-free H2O2 photosynthesis on organic-inorganic core-shell heterojunction under visible light irradiation

Artificial photosynthesis is a promising way to change light energy into chemical energy stored in hydrogen peroxide (H2O2). However, numerous heterojunction-based photocatalytic systems have substantially restricted effective H2O2 generation due to the intrinsic tendency toward fast charge recombination and the deficiency in active site population on the catalyst surface, especially under conditions not employing sacrificial agents. This study in situ prepared ZnIn2S4 (ZIS) nanoflowers onto a hollow covalent organic framework to strategically engineer a type-II organic-inorganic core-shell heterojunction photocatalyst, transforming O2 into H2O2. The heterojunction photocatalyst exhibited an exceptional H2O2 productivity of 3334 μmol g-1h-1 when no sacrificial agent was added, surpassing most reported systems. Mechanistic studies revealed that the heterojunctions extended the light absorption spectrum toward longer wavelengths and significantly increased the probability of electron transfer from photogenerated carriers to reactive species, which accelerated the reduction of O2 to H2O2. Furthermore, theoretical calculations confirmed that the heterojunction formation modified the coordination environment of the active sites on ZIS, fine-tuned the binding interaction between O2 and the catalyst interface, and reduced the energy barrier of intermediates, leading to superior performance. This study designed a novel, highly efficient organic-inorganic core-shell heterojunction photocatalyst and provided a promising strategy for enhancing the O2-to-H2O2 conversion.

Co-doping and N defect synergistically boosting 2e- oxygen reduction reaction on carbon nitride for full-day degradation of nitenpyram

Photocatalytic technology has garnered significant attention owing to its mild reaction conditions, broad applicability and lack of secondary pollution. However, its practical implementation in complex environments is significantly hindered by the stringent illumination requirements. Herein, a full-day photocatalysis-self-Fenton system was constructed by C, K co-doping and N defect jointly regulated graphitic carbon nitride (KCN-C). The experimental results demonstrate that the synthesized KCN-C not only enhances the efficiency of charge carrier separation, but also improves oxygen adsorption capacity and selectivity for the two-electron oxygen reduction reaction (2e- ORR). As a result, the KCN-C manifested remarkable photocatalytic hydrogen peroxide (H2O2) production efficiency, achieving a generation rate of 108.32 mM h-1 g-1 under illumination, which represents a 142.53-fold enhancement compared to pristine carbon nitride (CN). Notably, when nitenpyram (NTP) functions as an electron donor, the KCN-C demonstrates superior H2O2 production activity (3.52 mM h-1 g-1) while achieving a remarkable NTP degradation efficiency of 90 %. Moreover, the generated H2O2 can be subsequently activated to mineralize residual NTP and its intermediate products under dark conditions. This work provides novel insights into the rational design of full-day photocatalysis-self-Fenton systems for the efficient degradation of various refractory pollutants.

Formation of double-shelled hollow spherical CdS/Ca0.3Zn2.7In2S6 as S-scheme photocatalysts for highly efficient photocatalytic hydrogen evolution

While the configuration of most metal oxides hollow structures is well established, the synthesis of multinary metal sulfides with complex multi-shelled hollow structures remains in its infancy. Herein, we have developed a facile method to synthesize superhydrophilic Ca0.3Zn2.7In2S6 double-shelled hollow structures (DSHSs) with the assistance of trisodium citrate bilamellar vesicles, which manifests higher photocatalytic hydrogen generation rate compared with normal Ca0.3Zn2.7In2S6 single-shelled hollow structures and solid microflowers. Further construction of CdS/Ca0.3Zn2.7In2S6 S-scheme heterostructures by in situ photodeposition of CdS ultrafine nanoparticles on Ca0.3Zn2.7In2S6 DSHSs creates an intimate interface coupling and expansive contact region for fast interfacial charge transfer. Consequently, CdS/Ca0.3Zn2.7In2S6-5.0 composite exhibits a boosted photocatalytic H2 evolution of 30.08 mmol h-1 g-1, which is 2.7 times higher than Ca0.3Zn2.7In2S6 DSHSs (11.52 mmol h-1 g-1). Besides, the apparent quantum efficiency of CdS/Ca0.3Zn2.7In2S6-5.0 at 370 nm can reach 66.04 %. Moreover, CdS/Ca0.3Zn2.7In2S6-5.0 shows good stability for the hydrogen generation reaction. This elaborate design of CdS/Ca0.3Zn2.7In2S6-5.0 sheds light on the potential of integrating morphology modulation and S-scheme heterostructures construction with efficient solar energy utilization and optimized charge transfer for catalysis and optoelectronic applications.

Zn3In2S6/Bi3O4Br nanoflowers with oxygen vacancies and heterojunctions: A strategy for enhanced nitrofurazone photodegradation

The degradation of antibiotics in wastewater poses a critical environmental challenge, necessitating the development of advanced photocatalysts capable of efficiently generating active species. Hence, a novel Zn3In2S6/Bi3O4Br (ZB) heterojunction enriched with oxygen vacancies (OVs) was designed. The optimized ZB-1 (mass percentage of Bi3O4Br to Zn3In2S6 = 1 %) exhibited the highest nitrofurazone (NFZ) degradation rate constant (k) of 0.24 min-1 after 20 min illumination, which was 6.6 and 26.3 folds of the original Zn3In2S6 and Bi3O4Br, respectively. ZB-1 also demonstrated excellent cycling durability and resistance to pH fluctuation. The OVs potentiated O2 adsorption and drew the photogenerated electrons for oxygen (O2) activation, thereby enhancing carrier mobility. Furthermore, the constructed heterojunction facilitated light absorption and carrier migration for O2 activation. The OVs and heterojunctions collaboratively meliorated carrier utilization and active species generation. As a result, abundant superoxide radicals (O2-) were generated and significantly contributed to eliminating NFZ. Meanwhile, the photocatalytic mechanism was clarified by theoretical calculation. The degradation pathway of NFZ and the biotoxicity of its intermediates were systematically conjectured. This research provides a new perspective for designing efficient, durable, and reproducible photocatalysts, which can help address environmental issues related to antibiotic contamination.

Controllable macroscopic polarization induced asymmetric electron distribution in poly (heptazine imide) for enhanced overall photosynthesis of hydrogen peroxide in pure water

The incorporation of carbon nitride into photocatalytic technology creates a sustainable and pollution-free method for producing hydrogen peroxide (H2O2). Unfortunately, the efficiency of this process is greatly hindered by the sluggish separation of photo-generated carriers due to the weak internal electrical potential. To overcome this limitation, we present a promising strategy involving the fabrication of O-modulated poly(heptazine imide) (O-PHI), achieved through solid phase self-assembly aided by KSCN. This unique electron-rich polarization electric field induces asymmetric electron distribution, greatly enhancing the charge dynamics and facilitating enhanced photo-generated electron injection into active sites. As a result, when combined with CN units and oxygen functionalities that enhance oxygen adsorption, O-PHI exhibits superior H2O2 photosynthesis with a remarkable yield of 17.0 mmol g-1h-1 in pure water through both oxygen reduction and water oxidation routes, even up to 321.7 mmol g-1h-1 using a sacrificial reagent. These remarkable results demonstrate that the electron-rich polarization electric field outperforms the electron-deficient counterpart in H2O2 photosynthesis, surpassing the best known photocatalysts. This research represents a significant advancement in electron modification technology, leading to the design of more efficient metal-free photocatalysts for the production of valuable fuels.

Unlocking One-Step Two-Electron Oxygen Reduction via Metalloid Boron-Modified Zn3In2S6 for Efficient H2O2 Photosynthesis

The indirect two-step two-electron oxygen reduction reaction (2e- ORR) dominates photocatalytic H2O2 synthesis but suffers from sluggish kinetics, •O2 --induced catalyst degradation, and spatiotemporal carrier-intermediate mismatch. Herein, we pioneer a metal-metalloid dual-site strategy to unlock the direct one-step 2e- ORR pathway, demonstrated through boron-engineered Zn3In2S6 (B-ZnInS) photocatalyst with In-B dual-active sites. The In-B dual-site configuration creates a charge-balanced electron reservoir by charge complementation, which achieves moderate O2 adsorption via bidentate coordination and dual-channel electron transfer, preventing excessive O─O bond activation. Simultaneously, boron doping induces lattice polarization to establish a built-in electric field, quintupling photogenerated carrier lifetimes versus pristine ZnInS. These synergies redirect the O2 activation pathway from indirect to direct 2e- ORR process, delivering an exceptional H2O2 production rate of 3121 µmol g-1 h-1 in pure water under simulated AM 1.5G illumination (100 mW cm-2)-an 11-fold enhancement over ZnInS. The system achieves an unprecedented apparent quantum yield of 49.8% at 365 nm for H2O2 photosynthesis among inorganic semiconducting photocatalysts, and can continuously produce medical-grade H2O2 (3 wt%). This work provides insights for designing efficient H2O2 photocatalysts and beyond.

Spatially Separated Redox Centers in Anthraquinone-grafted Metal-Organic Frameworks for Efficient Piezo-photocatalytic H2O2 Production

Piezo-photocatalytic production of hydrogen peroxide (H2O2) from water and air is promising but its large-scale application is still challenging as insufficient reaction active sites and low reaction efficiency. We have applied molecular engineering methods to design an anthraquinone molecularly (AQ) grafted metal-organic framework piezo-photocatalyst (UiO-66-AQ) for H2O2 generation from water and air. The catalyst achieves a peak H2O2 yield of 7872.4 μM g-1 h-1 by facilitating two critical reactions: single-electron water oxidation (WOR) and two-electron oxygen reduction (ORR) on spatially separated redox sites. Experiments and computational simulations reveal efficient charge separation through a ligand-to-chain transfer mechanism. Electrons and holes are selectively transferred to AQ and UiO-66 promoting ORR and WOR under ultrasound and visible light. The high reaction rate of ORR (rapid generation of endoperoxide) compensates for the slow kinetics of WOR (generation of OH*) and greatly increases the rate of full-reaction of H2O2 production. Additionally, a continuous flow tubular reactor equipped with UiO-66-AQ catalytic membranes affords 96 % removal of organic dyes by a in situFenton process under visible light and water flow, confirming the significant potential of the catalyst for practical applications. This work deepens the understanding of directional carrier migration at piezo-photocatalytic spatial separation sites, opening new pathways for environmentally friendly and efficient H2O2 synthesis.

Verifying the Unique Charge Migration Pathway in Polymeric Homojunctions for Artificial Photosynthesis of Hydrogen Peroxide

Artificial photosynthesis for producing high-value hydrogen peroxide (H2O2) using carbon nitride-based systems holds immense potential. However, understanding the charge transfer dynamics in homojunction photocatalysts remains a significant challenge owing to the limitations of current characterization techniques. Here, a polymeric C3N5/C3N4 homojunction (CNHJ) is employed as a model system to probe interfacial electron transfer. Bimetallic cocatalysts serve as sensitive probes, enabling in situ tracking of the S-scheme electron transfer between C3N5 and C3N4 via X-ray photoelectron spectroscopy. Leveraging the unique advantages of this S-scheme, the CNHJ demonstrates substantially enhanced performance in the two-electron oxygen reduction reaction, achieving an impressive H2O2 production rate of 8.78 mmol g-1 h-1 under visible light irradiation. Furthermore, the system demonstrates robust performance in continuous-flow setups, under natural sunlight, and in photocatalytic disinfection tests, highlighting its practical potential. This approach offers new insights into dynamic electron transfer mechanisms and paves the way for advancing artificial photosynthesis technologies.

Construction of Hierarchical 2D-3D@3D Zn3In2S6@CdS Photocatalyst for Boosting Degradation of an Azo Dye

Herein, flower-like Zn3In2S6 (ZIS3) crystallites were grown onto acorn leaf-like CdS assemblies via a two-step hydrothermal approach. Under visible light irradiation, the Zn3In2S6-enriched heterostructures demonstrated an enhanced azo-dye degradation rate, with the majority of the organic analyte (Orange G) being degraded within 60 min. In contrast, the CdS-enriched hybrids showed poor photocatalytic performance. The optimized hybrid containing a nominal CdS content of 4 wt% was characterized by various physicochemical techniques, such as XRD, SEM, XPS and Raman. XPS analysis showed that the electron density around the Zn and In sites in Zn3In2S6 was slightly increased, implying a certain charge migration pattern. Complementary information from scavenging experiments suggested that hydroxy radicals were not the exclusive transient responsible for oxidative degradation of the organic azo-dye. This research provides new information about the development of metal chalcogenide-based heterostructures for efficient photocatalytic organic pollutant degradation.

Compressive interatomic distance stimulates photocatalytic oxygen-oxygen coupling to hydrogen peroxide

Photocatalytic hydrogen peroxide (H2O2) generation is largely subject to the sluggish conversion kinetics of the superoxide radical (O2⋅-) intermediate, which has relatively low reactivity and requires high energy. Here, we present a lattice-strain strategy to accelerate the conversion of O2⋅- to highly active singlet oxygen(1O2) by optimizing the distance between two adjacent active sites, thereby stimulating H2O2 generation via low-barrier oxygen-oxygen coupling. As the initial demonstration, the defect-induced strain in ZnIn2S4 nanosheet optimizes the distance of two adjacent Zn sites from 3.85 to 3.56 Å, resulting in that ZnIn2S4 with 0.7% compressive strain affords 3086.00 μmol g-1 h-1 yield of H2O2 with sacrificial agent. This performance is attributed to the strain-induced enhancement of electron coupling between the compressed adjacent Zn sites, which promotes low-barrier oxygen-oxygen coupling to active 1O2 intermediate. This finding paves the way for atomic-scale manipulation of reactive sites, offering a promising approach for efficient H2O2 photosynthesis.

Realizing C-C Coupling via Accumulation of C1 Intermediates within Dual-Vacancy-Induced Dipole-Limited Domain Field to Propel Photoreduction of CO2-to-C2 Fuel

Photocatalytic conversion of CO2 and H2O into high-value-added C2 fuels remains a tough challenge, mainly due to the insufficient concentration of photogenerated electrons for the instability of C1 intermediates, which often tend to desorb easily and disable to form C─C bonds. In this work, photoreduction of CO2-to-C2H6 is successfully achieved by introducing adjacent C, N dual-vacancy sites within the heptazine rings of ultrathin g-C3N4, which results in the opening of two neighboring heptazine rings and forms a distinctive dipole-limited domain field (DLDF) structure. In situ X-ray photoelectron spectra and in situ fourier transform infrared spectra provide direct evidence of the rapid accumulation and transformation of C1 intermediates, especially CO* and CHO*, within the DLDF. Ab initio molecular dynamics further substantiates the role of DLDF in promoting C-C coupling between CO* and CHO*, through the analysis of interaction trajectories and energy changes of their central atoms, ultimately achieving a high yield of C2H6 up to 57.86 µmol g-1 h-1. It is for the first time to propose the concept of DLDF for significant advancement in photoreduction of CO2-to-C2 fuel with the evident breakthrough to address the challenge of coupling carbon-containing intermediates between active sites, offering new insights for the design of C-C coupling sites in single-component photocatalysts.

Photocatalytic Methanol Dehydrogenation with Switchable Selectivity

Switchable selectivity achieved by altering reaction conditions within the same photocatalytic system offers great advantages for sustainable chemical transformations and renewable energy conversion. In this study, we investigate an efficient photocatalytic methanol dehydrogenation with controlled selectivity by varying the concentration of nickel cocatalyst, using zinc indium sulfide nanocrystals as a semiconductor photocatalyst, which enables the production of either formaldehyde or ethylene glycol with high selectivity. Control experiments revealed that formaldehyde is initially generated and can either serve as a terminal product or intermediate in producing ethylene glycol, depending on the nickel concentration in the solution. Mechanistic studies suggest a unique role of ionic nickel as an additional photoelectron competitor that can significantly influence selectivity, alongside its well-established function as a hydrogen evolution reaction cocatalyst under photocatalytic conditions. The demonstrated switchable selectivity provides a new tool for producing diverse products from methanol, while advancing the understanding of cocatalyst behavior for versatile catalytic performance.

Synergistic effect between sulfur vacancies and S-scheme heterojunctions in WO3/VS-Zn3In2S6 for enhanced photocatalytic CO2 reduction in H2O vapor

Converting CO2 into CO, CH4, and other hydrocarbons using solar energy presents a viable approach for addressing energy shortages. In this study, photocatalysts with S-deficient WO3/Zn3In2S6 (WO3/VS-ZIS) S-scheme heterojunctions have been successfully synthesized. Under UV-vis light irradiation, 20 %WO3/VS-ZIS demonstrated significantly improved CO2 reduction activity and CH4 selectivity. Detailed characterization and density functional theory (DFT) calculations reveal that the enhanced performance is due to the synergistic optimization of the S-scheme heterojunction and sulfur vacancies (VS) for CO2 reduction. The presence of VS aids in the adsorption and activation of CO2 and enhances the separation of charge carriers. The 2D/2D S-scheme heterostructure assembled with WO3 nanosheets not only accelerates the migration and separation of photoexcited charge carriers but also improves the adsorption of H2O and the formation of VS, thereby increasing the adsorption and activation of CO2 and facilitating the protonation of CO* to produce CH4. This study clarifies the synergistic effect of VS and S-scheme heterostructures in improving photocatalytic performance, offering valuable insights into the photoactivation process of CO2 at VS in S-scheme heterojunctions.

Indium oxide-based Z-scheme hollow core-shell heterostructure with rich sulfur-vacancy for highly efficient light-driven splitting of water to produce clean energy

Crafting an inorganic semiconductor heterojunction with defect engineering and morphology modulation is a strategic approach to produce clean energy by the highly efficient light-driven splitting of water. In this paper, a novel Z-scheme sulfur-vacancy containing Zn3In2S6 (Vs-Zn3In2S6) nanosheets/In2O3 hollow hexagonal prisms heterostructrue (Vs-ZIS6INO) was firstly constructed by an oil bath method, in which Vs-Zn3In2S6 nanosheets grew on the surfaces of In2O3 hollow hexagonal prisms to form a hollow core-shell structure. The obtained Vs-ZIS6INO heterostructrue exhibited much enhanced activity of the production of H2 and H2O2 by the light-driven water splitting. In particular, under visible light irradiation (λ > 420 nm), the rate of generation of H2 of Vs-ZIS6INO sample containing 30 wt% Vs-Zn3In2S6 (30Vs-ZIS6INO) could reach 3721 μmol g-1h-1, which was 87 and 6 times higher than those of Zn3In2S6 (43 μmol g-1h-1) and Vs-Zn3In2S6 (586 μmol g-1h-1), respectively. Meanwhile, 30Vs-ZIS6INO could exhibit the rate of H2O2 production of 483 μmol g-1h-1 through the dual pathways of indirect 2e- oxygen reduction (ORR) and water oxidation (WOR) without adding any sacrifice agents, far exceeding In2O3 (7 μmol g-1h-1) and Vs-Zn3In2S6 (58 μmol g-1h-1). The excellent photocatalytic activities of H2 and H2O2 generations of Vs-ZIS6INO sample might result from the synergistic effect of the sulfur vacancy, hollow core-shell structure, and Z-scheme heterostructure, which accelerated the electron delocalization, enhanced the absorption and conversion of solar energy, reduced the carrier diffusion distance, and ensured high REDOX ability. In addition, the possible photocatalytic mechanisms for the production of H2 and H2O2 were discussed in detail. This study provided a new idea and reference for constructing the novel and efficient inorganic semiconductor heterostructures by coordinating vacancy defect and morphology design to adequately utilize water splitting for the production of clean energy.

Lattice Defects and Electronic Modulation of Flower-Like Zn3In2S6 Promote Photocatalytic Degradation of Multiple Antibiotics

Photocatalysis is an effective technique to remove antibiotic residues from aquatic environments. Typical metal sulfides like Zn3In2S6 have been applied to a wide range of photocatalytic applications. However, there are currently no readily accessible methods to increase its antibiotic-degrading activity. Here, a facile hydrothermal approach is developed for the preparation of flower-like Zn3In2S6 with tunable sulfur lattice defects. Photogenerated carriers can be separated and transferred more easily when there is an adequate amount of lattice defects. Moreover, lattice defect-induced electronic modulation enhances light utilization and adsorption properties. The modified Zn3In2S6 demonstrates outstanding photocatalytic degradation activity for levofloxacin, ofloxacin, and tetracycline. This work sheds light on exploring metal sulfides with sulfur lattice defects for enhancing photocatalytic activity.

Accelerated Solar-Driven Polyolefin Degradation via Self-Activated Hydroxy-Rich ZnIn2S4

Degradation of polyolefin (PE) plastic by a traditional chemical method requires a high pressure and a high temperature but generates complex products. Here, sulfur vacancy-rich ZnIn2S4 and hydroxy-rich ZnIn2S4 were rationally fabricated to realize photocatalytic degradation of PE in an aqueous solution under mild conditions. The results reveal that the optimized photocatalyst could degrade PE into CO2 and CO, and PE had a weight loss of 84.5% after reaction for 60 h. Systematic experiments confirm that the synergetic effect of hydroxyl groups and S vacancies contributes to improve the photocatalytic degradation properties of plastic wastes. In-depth investigation illustrates that the active radicals attack (h+ and •OH) weak spots (C-H and C-C bonds) of the PE chain to form CO2, which is further selectively photoreduced to CO. Multimodule synergistic tandem catalysis can further improve the utilization value of plastic wastes; for example, product CO2/CO in the plastic degradation process can be converted in situ into HCOOH by coupling with electrocatalytic technology.

Immuno-Nanocomplexes Target Heterogenous Network of Inflammation and Immunity in Myocardial Infarction

Despite the proceeds in the management of acute myocardial infarction (AMI), the current therapeutic landscape still suffers from limited success in the clinic. Exaggerated inflammatory immune response and excessive oxidative stress are key pathological features aggravating myocardium damage. Herein, catalytic immunomodulatory nanocomplexes as anti-AMI therapeutics to resolve reactive oxygen species (ROS)-proinflammatory neutrophils-specific-inflammation is engineered. The nanocomplexes contain lyophilic S100A8/9 inhibitor ABR2575 in the core of nanoemulsions, which effectively disrupts the neutrophils-S100A8/A9-inflammation signaling pathway in the AMI microenvironment. Additionally, ROS scavenger ultrasmall CuxO nanoparticles are incorporated into the nanoemulsions via coordinating with SH groups of poly(ethylene glycol) (PEG)-conjugated lipids, which mimic multiple enzymes, dramatically alleviating the oxidative stress damage to myocardial tissue. This combination strategy significantly suppresses the infiltration of pro-inflammatory monocytes, macrophages, and neutrophils, as well as the secretion of inflammatory cytokines. Additionally, it potentially triggers cardiac Tert activation, which promotes myocardial function and decreases infarction size in preclinical murine AMI models. This approach offers a new nanomedicine for treating AMI, resulting in a dramatically enhanced therapeutic outcome.

Visible light-driven molecular oxygen activation for oxidative amidation of alcohols using lead-free metal halide perovskite

Herein, we report the modulation of the band structures of halide perovskite Cs2CuBr4 by tuning the synthesis methods. The photocatalyst PC-1, synthesized by the hot injection method, has a more negative conduction band minima (CBM) than the photocatalyst PC-2, synthesized at room temperature. As a result, PC-1 can activate molecular O2 more efficiently to initiate the radical-mediated dehydrogenation of alcohols. The more positive valence band maxima (VBM) of PC-1 also facilitates amine oxidation to the corresponding radical. Further, improved charge separation and transport and a decrement in the photogenerated charge carrier recombination have been detected for PC-1 to enhance photocatalytic activity. PC-1 showed improved yields for a series of structurally diverse amides (highest yield = 98%) by oxidative amidation of alcohols under visible light irradiation.

Deciphering charge transfer dynamics of a lead halide perovskite-nickel(ii) complex for visible light photoredox C-N coupling

Photoredox catalysis involving perovskite quantum dots (QDs) has gained enormous attention because of their high efficiency and selectivity. In this study, we have demonstrated CsPbBr3 QDs as photocatalysts for the C-N bond formation reaction. The introduction of Ni(dmgH)2 (dmgH = dimethyl glyoximato) as a cocatalyst with CsPbBr3 QDs facilitates photocatalytic C-N coupling to form a wide variety of amides. The optimized interaction between the cocatalyst and photocatalyst enhances charge transfer and mitigates charge recombination, ultimately boosting photocatalytic performance. The photocatalytic activity is notably influenced by the variation in the amount of cocatalyst and 7 wt% Ni(dmgH)2 produces the best yield (92%) of amide. Femtosecond transient absorption spectroscopy reveals that the dynamics of the trap states of QDs are affected by cocatalyst. Further, Ni(dmgH)2 facilitates molecular oxygen activation to form superoxide radicals, which further initiates the radical pathway for the C-N coupling.

Amorphizing MnIn2S4 Atomic Layers Create an Asymmetrical InO1S5 Polarization Plane for Photocatalytic Ammonia Synthesis and CO2 Reduction

Building a polarization center is an effective avenue to boost charge separation and molecular activation in photocatalysis. However, a limited number of polarization centers are usually created. Here, a polarization plane based on two-dimensional (2D) atomic layers is designed to maximize the surface polarization centers. The Mn in a 2D crystal lattice is etched from the MnIn2S4 atomic layers to build a consecutive symmetry-breaking structure of isolated InO1S5 sites. More charges aggregate around O, making the isolated InO1S5 sites highly polarized. Due to the formation of the InO1S5 polarization plane, an enormous polarized electric field is formed perpendicular to the 2D atomic layers and the carrier lifetime can be prolonged from 93.2 ps in MnIn2S4 to 1130 ps in amorphous MnxIn2Sy. Meantime, the formed large charge density gradient favors coupling and activation of small molecules. Benefiting from these features, a good NH3 photosynthesis performance (515.8 μmol g-1 h-1) can be realized over amorphous MnxIn2Sy, roughly 2.5 and 48.9 times higher than those of MnIn2S4 atomic layers and bulk MnIn2S4, respectively. The apparent quantum yields reach 5.4 and 3.3% at 380 and 400 nm, respectively. Meanwhile, a greatly improved CO2 reduction activity is also achieved over MnxIn2Sy. This strategy provides an accessible pathway for designing an asymmetrical polarization plane to motivate photocatalysis optimization.

Protonation of an Imine-linked Covalent Organic Framework for Efficient H2O2 Photosynthesis under Visible Light up to 700 nm

Covalent organic frameworks (COFs) are promising photocatalysts for H2O2 production from water via oxygen reduction reaction (ORR). The design of COFs for efficient H2O2 production indubitably hinges on an in-depth understanding of their ORR mechanisms. In this work, taking an imine-linked COF as an example, we demonstrate that protonation of the functional units such as imine, amine, and triazine, is a highly efficient strategy to upgrade the activity levels for H2O2 synthesis. The protonation not only extends the light absorption of the COF but also provides proton sources that directly participate in H2O2 generation. Notably, the protonation simplifies the reaction pathways of ORR to H2O2, i.e. from an indirect superoxide radical (O 2 • - ${{O}_{2}^{\bullet -}}$ ) mediated route to a direct one-step two-electron route. Theoretical calculations confirm that the protonation favors H2O2 synthesis due to easy access of protons near the reaction sites that removes the energy barrier for generating *OOH intermediate. These findings not only extend the mechanistic insight into H2O2 photosynthesis but also provide a rational guideline for the design and upgradation of efficient COFs.

Hydroxyl-Bonded Co Single Atom Site on Boroncarbonitride Surface Realizes Nonsacrificial H2O2 Synthesis in the Near-Infrared Region

Photocatalytic synthesis of hydrogen peroxide (H2O2) from O2 and H2O under near-infrared light is a sustainable renewable energy production strategy, but challenging reaction. The bottleneck of this reaction lies in the regulation of O2 reduction path by photocatalyst. Herein, the center of the one-step two-electron reduction (OSR) pathway of O2 for H2O2 evolution via the formation of the hydroxyl-bonded Co single-atom sites on boroncarbonitride surface (BCN-OH2/Co1) is constructed. The experimental and theoretical prediction results confirm that the hydroxyl group on the surface and the electronic band structure of BCN-OH2/Co1 are the key factor in regulating the O2 reduction pathway. In addition, the hydroxyl-bonded Co single-atom sites can further enrich O2 molecules with more electrons, which can avoid the one-electron reduction of O2 to •O2 -, thus promoting the direct two-electron activation hydrogenation of O2. Consequently, BCN-OH2/Co1 exhibits a high H2O2 evolution apparent quantum efficiency of 0.8% at 850 nm, better than most of the previously reported photocatalysts. This study reveals an important reaction pathway for the generation of H2O2, emphasizing that precise control of the active site structure of the photocatalyst is essential for achieving efficient conversion of solar-to-chemical.

Surface Reconstruction for Selective Oxidation of Tetrahydroisoquinoline

Integration of hydrogen evolution with the oxidation of organic substances in one electrochemical system is highly desirable. However, achieving selective oxidation of organic substances in the integrated system is still highly challenging. In this study, a phosphorylated NiMoO4 nanoneedle-like array was designed as the catalytic active electrode for the integration of highly selective electrochemical dehydrogenation of tetrahydroisoquinolines (THIQs) with hydrogen production. The leaching of anions, including MoO42- and PO43-, facilitates the reconstruction of the catalyst. As a result, nickel oxyhydroxides with the doping of PO43- and richness of defects are in situ formed. In situ Raman and density functional theory calculations have shown that the high catalytic activity is attributed to the in situ formed PO43- involved NiOOH substance. In the dehydrogenation process, the involved C-H bond but not the N-H bond is first destroyed. A two-electrode system was then fabricated with the optimized electrode that shows a benchmark current density of 10 mA cm-2 at 1.783 V, providing a yield of 70% for dihydroisoquinolines. A robust stability was also shown for this integrated electrochemical system. The understanding of the reconstruction behavior and the achievement of selective dehydrogenation will provide some hints for electrochemical synthesis.

Tailoring Charge Separation in ZnIn2S4@CdS Hollow Nanocages for Simultaneous Alcohol Oxidation and CO2 Reduction under Visible Light

Artificial photosynthesis provides a sustainable strategy for producing usable fuels and fine chemicals and attracts broad research interest. However, conventional approaches suffer from low reactivity or low selectivity. Herein, we demonstrate that photocatalytic reduction of CO2 coupled with selective oxidation of aromatic alcohol into corresponding syngas and aromatic aldehydes can be processed efficiently and fantastically over the designed S-scheme ZnIn2S4@CdS core-shell hollow nanocage under visible light. In the ZnIn2S4@CdS heterostructure, the photoexcited electrons and holes with weak redox capacities are eliminated, while the photoexcited electrons and holes with powder redox capacities are separated spatially and preserved on the desired active sites. Therefore, even if there are no cocatalysts and no vacancies, ZnIn2S4@CdS exhibits high reactivity. For instance, the CO production of ZnIn2S4@CdS is about 3.2 and 3.4 times higher than that of pure CdS and ZnIn2S4, respectively. More importantly, ZnIn2S4@CdS exhibits general applicability and high photocatalytic stability. Trapping agent experiments, 13CO2 isotopic tracing, in situ characterizations, and theoretical calculations reveal the photocatalytic mechanism. This study provides a new strategy to design efficient and selective photocatalysts for dual-function redox reactions by tailoring the active sites and regulating vector separation of photoexcited charge carriers.

Structure Engineered High Piezo-Photoelectronic Performance for Boosted Sono-Photodynamic Therapy

Sono-photodynamic therapy is hindered by the limited tissue penetration depth of the external light source and the quick recombination of electron-hole owing to the random movement of charge carriers. In this study, orthorhombic ZnSnO3 quantum dots (QDs) with piezo-photoelectronic effects are successfully encapsulated in hexagonal upconversion nanoparticles (UCNPs) using a one-pot thermal decomposition method to form an all-in-one watermelon-like structured sono-photosensitizer (ZnSnO3 @UCNPs). The excited near-infrared light has high penetration depth, and the watermelon-like structure allows for full contact between the UCNPs and ZnSnO3 QDs, achieving ultrahigh Förster resonance energy transfer efficiency of up to 80.30%. Upon ultrasonic and near-infrared laser co-activation, the high temperature and pressure generated lead to the deformation of the UCNPs, thereby driving the deformation of all ZnSnO3 QDs inside the UCNPs, forming many small internal electric fields similar to isotropic electric domains. This piezoelectric effect not only increases the internal electric field intensity of the entire material but also prevents random movement and rapid recombination of charge carriers, thereby achieving satisfactory piezocatalytic performance. By combining the photodynamic effect arising from the energy transfer from UCNPs to ZnSnO3 , synergistic efficacy is realized. This study proposes a novel strategy for designing highly efficient sono-photosensitizers through structural design.

Photothermal Synergistic Catalysis over Defective Zn3In2S6 for CO2 Fixation

Carbon dioxide (CO2) cycloaddition not only produces highly valued cyclic carbonate but also utilizes CO2 as C1 resources with 100% atomic efficiency. However, traditional catalytic routes still suffer from inferior catalytic efficiency and harsh reaction conditions. Developing multienergy-field catalytic technology with expected efficiency offers great opportunity for satisfied yield under mild conditions. Herein, Zn3In2S6 with sulfur vacancies (Sv) was fabricated with the assistance of cetyltrimethylammonium bromide (CTAB), which is further employed for photothermally driven CO2 cycloaddition first. Photoluminescence spectroscopy and photoelectrochemical characterization demonstrated its superior separation kinetics of photoinduced carriers induced by defect engineering. The temperature-programmed desorption (TPD) technique indicated its excellent Lewis acidity-basicity characters. Due to the combination of above merits from photocatalysis and thermal catalysis, defective Zn3In2S6-Sv achieved a yield as high as 73.2% for cyclic carbonate at 80 °C under blue LED illumination within 2 h (apparent quantum yield of 0.468% under illumination of 380 nm monochromatic light at 36 mW·cm-2), which is 2.9, 2.0, and 6.9 times higher than that in dark conditions and those of pristine Zn3In2S6 and industrial representative tetrabutylammonium bromide (TBAB) thermal-catalysis process under the same conditions, respectively. The synergistic reaction path of photocatalysis and thermal catalysis was discriminated by theoretical calculation. This work provides new insights into the photothermal synergistic catalysis CO2 cycloaddition with defective ternary metal sulfides.

Rational Design of Conjugated Acetylenic Polymers Enables a Two-Electron Water Oxidation Pathway for Enhanced Photosynthetic Hydrogen Peroxide Generation

Herein, the design of conjugated acetylenic polymers (CAPs) featuring diverse spatial arrangements and intramolecular spacers of diacetylene moieties (─C≡C─C≡C─) for photocatalytic hydrogen peroxide (H2 O2 ) production from water and O2 , without the need for sacrificial agents, is presented. It is shown that the linear configuration of diacetylene moieties within conjugated acetylenic polymers (CAPs) induces a pronounced polarization of electron distribution, which imparts enhanced charge-carrier mobility when compared to CAPs' networks featuring cross-linked arrangements. Moreover, optimizing the intramolecular spacer between diacetylene moieties within the linear structure leads to the exceptional modulation of the band structures, specifically resulting in a downshifted valence band (VB) and rendering the two-electron water oxidation pathway thermodynamically feasible for H2 O2 production. Consequently, the optimized CAPs with a linear configuration (LCAP-2), featuring spatially separated reduction centers (benzene rings) and oxidation centers (diacetylene moieties), exhibit a remarkable H2 O2 yield rate of 920.1 µmol g-1 h-1 , superior than that of the linear LCAP-1 (593.2 µmol g-1 h-1 ) and the cross-linked CCAP (433.4 µmol g-1 h-1 ). The apparent quantum efficiency (AQE) and solar-to-chemical energy conversion (SCC) efficiency of LCAP-2 are calculated to be 9.1% (λ = 420 nm) and 0.59%, respectively, surpassing the performance of most previously reported conjugated polymers.

Pauling-Type Adsorption of O2 Induced by Heteroatom Doped ZnIn2 S4 for Boosted Solar-Driven H2 O2 Production

Breaking the trade-off between activity and selectivity has perennially been a formidable endeavor in the field of hydrogen peroxide (H2 O2 ) photosynthesis, especially the side-on configuration of oxygen (O2 ) on the catalyst surface will cause the cleavage of O-O bonds, which drastically hinders the H2 O2 production performance. Herein, we present an atomically heteroatom P doped ZnIn2 S4 catalyst with tunable oxygen adsorption configuration to accelerate the ORR kinetics essential for solar-driven H2 O2 production. Indeed, the spectroscopy characterizations (such as EXAFS and in situ FTIR) and DFT calculations reveal that heteroatom P doped ZnIn2 S4 at substitutional and interstitial sites, which not only optimizes the coordination environment of Zn active sites, but also facilitates electron transfer to the Zn sites and improves charge density, avoiding the breakage of O-O bonds and reducing the energy barriers to H2 O2 production. As a result, the oxygen adsorption configuration is regulated from side-on (Yeager-type) to end-on (Pauling-type), resulting in the accelerated ORR kinetics from 874.94 to 2107.66 μmol g-1  h-1 . This finding offers a new avenue toward strategic tailoring oxygen adsorption configuration by the rational design of doped photocatalyst.

Selective Oxidation of 5-Hydroxymethyl Furfural Coupled with H2 Production over Surface Sulfur Vacancy-Rich Zn3In2S6/Bi2MoO6 Heterojunction Photocatalyst

The construction of heterojunctions and surface defects is a promising strategy for enhancing photocatalytic activity. A surface sulfur vacancy (VS)-rich Zn3In2S6/Bi2MoO6 heterojunction photocatalyst (ZIS-VS/BMO) was herein developed for the selective oxidation of biomass-derived 5-hydroxymethyl furfural (HMF) to value-added 2,5-diformylfuran (DFF) coupled with H2 production. The ZIS-VS/BMO heterojunction consisted of Bi2MoO6 (BMO) with preferentially exposed high-index (131) facets and VS-rich two-dimensional (2D) Zn3In2S6 (ZIS-VS) nanosheets with preferentially exposed high-index (102) facets. The directional transfer of light-driven electrons from BMO to ZIS-VS occurs in the heterojunction interface, as confirmed by an in situ irradiated XPS (ISI-XPS) measurement, which facilitates the electron-hole separation. The benefits of VS in activating HMF, suppressing overoxidation of DFF, and accelerating electron transport were disclosed by molecular simulation. ZIS-VS/BMO displays outstanding performance with a DFF yield of 74.1% and a DFF selectivity of 90%, as well as a rapid rate of H2 evolution. This research would help design highly efficient photocatalysts and develop a new technology for biomass resource utilization.

Designing Surface-Defect Engineering to Enhance the Solar-Driven Conversion of CO2 to C2 Products over Zn3In2S6/ZnS

The manipulation of electronic structure and prevention of photogenerated carriers from being quenched in bulk defects during the photocatalytic CO2 reduction reaction (CRR) have been effectively demonstrated through surface vacancy and defect engineering. In this work, the electronic structure on the surface of Zn3In2S6/ZnS (ZIS/ZnS) is significantly modified by the introduction and control of the surface S vacancies (SV) through Ar-plasma treatment. EPR and XPS analyses confirmed that SV was exclusively present on the ZIS/ZnS surface. The resulting ZIS/ZnS heterojunction photocatalysts demonstrate an impressive 46.6% selectivity toward C2 products even in the absence of cocatalysts. The mechanism of photocatalytic CRR is further elucidated through in situ analysis. Theoretical calculations demonstrate that the presence of In and Zn atoms adjacent to SV significantly enhances the adsorption of CO2 and facilitates C-C coupling.

Developing Ni single-atom sites in carbon nitride for efficient photocatalytic H2O2 production

Photocatalytic two-electron oxygen reduction to produce high-value hydrogen peroxide (H2O2) is gaining popularity as a promising avenue of research. However, structural evolution mechanisms of catalytically active sites in the entire photosynthetic H2O2 system remains unclear and seriously hinders the development of highly-active and stable H2O2 photocatalysts. Herein, we report a high-loading Ni single-atom photocatalyst for efficient H2O2 synthesis in pure water, achieving an apparent quantum yield of 10.9% at 420 nm and a solar-to-chemical conversion efficiency of 0.82%. Importantly, using in situ synchrotron X-ray absorption spectroscopy and Raman spectroscopy we directly observe that initial Ni-N3 sites dynamically transform into high-valent O1-Ni-N2 sites after O2 adsorption and further evolve to form a key *OOH intermediate before finally forming HOO-Ni-N2. Theoretical calculations and experiments further reveal that the evolution of the active sites structure reduces the formation energy barrier of *OOH and suppresses the O=O bond dissociation, leading to improved H2O2 production activity and selectivity.

Synergistic Metal-Nonmetal Active Sites in a Metal-Organic Cage for Efficient Photocatalytic Synthesis of Hydrogen Peroxide in Pure Water

Photocatalytic synthesis of hydrogen peroxide (H2 O2 ) is a potential clean method, but the long distance between the oxidation and reduction sites in photocatalysts hinders the rapid transfer of photogenerated charges, limiting the improvement of its performance. Here, a metal-organic cage photocatalyst, Co14 (L-CH3 )24 , is constructed by directly coordinating metal sites (Co sites) used for the O2 reduction reaction (ORR) with non-metallic sites (imidazole sites of ligands) used for the H2 O oxidation reaction (WOR), which shortens the transport path of photogenerated electrons and holes, and improves the transport efficiency of charges and activity of the photocatalyst. Therefore, it can be used as an efficient photocatalyst with a rate of as high as 146.6 μmol g-1  h-1 for H2 O2 production under O2 -saturated pure water without sacrificial agents. Significantly, the combination of photocatalytic experiments and theoretical calculations proves that the functionalized modification of ligands is more conducive to adsorbing key intermediates (*OH for WOR and *HOOH for ORR), resulting in better performance. This work proposed a new catalytic strategy for the first time; i.e., to build a synergistic metal-nonmetal active site in the crystalline catalyst and use the host-guest chemistry inherent in the metal-organic cage (MOC)to increase the contact between the substrate and the catalytically active site, and finally achieve efficient photocatalytic H2 O2 synthesis.

Regulation of Redox Molecular Junctions in Covalent Organic Frameworks for H2 O2 Photosynthesis Coupled with Biomass Valorization

H2 O2 photosynthesis coupled with biomass valorization can not only maximize the energy utilization but also realize the production of value-added products. Here, a series of COFs (i.e. Cu3 -BT-COF, Cu3 -pT-COF and TFP-BT-COF) with regulated redox molecular junctions have been prepared to study H2 O2 photosynthesis coupled with furfuryl alcohol (FFA) photo-oxidation to furoic acid (FA). The FA generation efficiency of Cu3 -BT-COF was found to be 575 mM g-1 (conversion ≈100 % and selectivity >99 %) and the H2 O2 production rate can reach up to 187 000 μM g-1 , which is much higher than Cu3 -pT-COF, TFP-BT-COF and its monomers. As shown by theoretical calculations, the covalent coupling of the Cu cluster and the thiazole group can promote charge transfer, substrate activation and FFA dehydrogenation, thus boosting both the kinetics of H2 O2 production and FFA photo-oxidation to increase the efficiency. This is the first report about COFs for H2 O2 photosynthesis coupled with biomass valorization, which might facilitate the exploration of porous-crystalline catalysts in this field.

Construction of ZnO/Zn3In2S6/Pt with integrated S-scheme/Schottky heterojunctions for boosting photocatalytic hydrogen evolution and bisphenol a degradation

Photocatalytic water splitting has been identified as a promising solution to tackle the current environmental and energy crisis in the world. However, the challenge of this green technology is the inefficient separation and utilization of photogenerated electron-hole pairs in photocatalysts. To overcome this challenge in one system, a ternary ZnO/Zn₃In₂S₆/Pt material was prepared as a photocatalyst using a stepwise hydrothermal process and in-situ photoreduction deposition. The integrated S-scheme/Schottky heterojunction in the constructed ZnO/Zn₃In₂S₆/Pt photocatalyst enabled it to exhibit efficient photoexcited charge separation/transfer. The evolved H₂ reached up to 3.5 mmol g^-1h^-1. Meanwhile, the ternary composite possessed a high cyclic stability against photo-corrosion under irradiation. Practically, the ZnO/Zn₃In₂S₆/Pt photocatalyst also showed great potential for H₂ evolution while simultaneously degrading organic contaminants like bisphenol A. It is hoped in this work that the incorporation of Schottky junctions and S-scheme heterostructures in the construction of photocatalysts would lead to accelerated electron transfer and high photoinduced electron-hole pair separation, respectively, to synergistically enhance the performance of photocatalysts.