Molecule Self-Assembly Synthesis of Porous Few-Layer Carbon Nitride for Highly Efficient Photoredox Catalysis

General self-fission strategy via supramolecular self-assembly for high-yield and cost-effective synthesis of g-C3N4 nanostructures for photocatalytic hydrogen evolution

Graphitic carbon nitride (g-C3N4) is one of the most promising candidates as a photocatalyst. However, the practical application of g-C3N4 has been hindered by its high-cost, low-yield synthesis methods. Herein, we develop a high-yield, cost-effective synthesis strategy for fabricating g-C3N4 nanostructures by low-temperature (430 °C) air pre-etching, which can induce the self-fission of supramolecular precursors (SMPs). This new synthesis strategy can achieve a production yield of ∼35 wt% and ∼41 wt% for g-C3N4 nanosheets (CNs) and sulfur-doped g-C3N4 nanotubes (SCNt), notably higher than the yields of conventional methods (<10 wt%). The underlying mechanism for the higher production yield is that this low-temperature etching method can effectively slow down the decomposition rate of SMPs and in this way promote their polymerization into g-C3N4. The pre-etching method can significantly increase the specific surface areas of the obtained sample, resulting in higher BET values of CNs (132.7 m2 g-1) and SCNt (112.9 m2 g-1), which are 2.5 and 3.2 times those for the samples without pre-etching treatment. Moreover, the as-prepared nanostructures exhibit remarkable photocatalytic performance, with hydrogen production rates of 1464.2 and 2883.4 μmol h-1 g-1 for CNs and SCNt, respectively, achieving 10.2- and 20.1-fold enhancements over bulk g-C3N4. In addition, the successful synthesis of nanosheets from 2,4,6-triaminopyrimidine-cyanuric acid and commercially available melamine-cyanurate precursors further demonstrates the broad applicability of this strategy. Notably, the successful synthesis of 70 g of CNs confirms that the proposed strategy is capable of large-scale production of novel photocatalysts. This scalable and economical strategy lays a solid foundation for future industrial applications of g-C3N4-based photocatalysts.

Ionic liquid gating-induced defect passivation and enhanced photocatalytic performance in graphitic carbon nitride (g-C3N4) semiconductors

Ionic liquid gating (ILG) is an emergent technique for controlling multiple types of ionic doping and leads to numerous attractive physical properties in quantum materials. This study widens its intriguing applications in metal-free graphitic carbon nitride (g-C3N4) semiconductor which is distinct by various extrinsic defects (vacancies, interlayer defects, etc) and intrinsic defects (irregular melon chains, dangling bonds, etc.). Here, the efficient passivation of defects is realized in g-C3N4through combined electrostatic and electrochemical mechanisms. By optimizing the ionic liquid concentration and applying a negative electric field, the gated g-C3N4exhibit a changed local bonding environment, an increased bandgap, as well as a suppression of photoluminescence (PL) intensity over 80%. Our results demonstrate that the charged ions from the mixed electrolyte passivate the charged defect centers, redistribute the charges within the g-C3N4framework, leading to the improved photogenerated carries separation, which is verified by the enhanced photocatalytic efficiency of treated g-C3N4. In particular, the changes of the density of states near the Fermi level reflect ionic interaction induced defect passivation in g-C3N4, which plays a key role in regulating its PL properties. These findings provide novel insights in ILG mechanisms in layered porous materials and shed light on its potential prospects in other semiconductors with controlled defect engineering.

Gas-Template Synthesis of Ultrathin Porous Carbon Nitrides for Photocatalytic Redox Reactions

Graphitic carbon nitride (g-C3N4) has emerged as a promising metal-free photocatalyst but is plagued by its low activity owing to a high electron-hole recombination rate and small specific surface area. A specialized gas-template method was successfully employed to synthesize an ultrathin porous carbon nitride (UPCN) photocatalyst containing nitrogen vacancies. This thermally induced exfoliation and polycondensation approach can be modulated using different gas templates. Compared with bulk g-C3N4, UPCNs feature an optimized ultrathin structure, larger surface area, weaker fluorescence intensity, lower impedance, and higher photocurrent response. These properties contribute to more exposed active sites, shorter diffusion paths for both ions and electrons, and improved carrier separation. Consequently, UPCNs exhibit considerably enhanced photocatalytic performance in both the hydrogen evolution reaction (HER) and the photooxidation of 2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylic ester (1,4-DHP) under visible light. Among UPCNs, TPA-UPCN (tetrapropylammonium chloride as the gas template) exhibits the highest photocatalytic activity, surpassing NH4Cl-templated carbon nitrides (2747 vs 2092 μmol·g-1·h-1) in HER. Moreover, TPA-UPCN achieves unprecedented photocatalytic oxidation efficiency for 1,4-DHP. This study provides a new approach for the preparation of UPCN materials with enhanced photocatalytic performance.

Defective Poly(heptazine imide) Nanosheets for Efficient One-Step Two-Electron Photocatalytic O2 Reduction to Medical-Like H2O2

Poly(heptazine imide) (PHI) is a promising photocatalyst for hydrogen peroxide (H2O2) production; however, enhancing its specific surface area to expose internal active sites and understanding their roles in key mechanistic steps for the H2O2 synthesis remain challenging. Here, we utilized organic cations to exfoliate bulk PHI and fabricate PHI nanosheets for producing H2O2 at a rate of 27.35 mmol g-1 h-1 under simulated solar light irradiation, outperforming most of the reported carbon nitride-based catalysts. Importantly, after 36 h of cyclic accumulation reactions in a self-created spiral flow reactor, the H2O2 concentration stabilized at 2.7 wt.%, close to medical sterilization levels. In situ spectroscopic characterizations and density functional theory calculations revealed that the exfoliation results in molecular reconfiguration of the PHI basal planes, forming the active sites to promote charge separation and electron localization. This new structure also creates midgap states, enabling direct H2O2 production via a one-step, two-electron pathway, bypassing the superoxide radical pathway. Theoretical calculations suggest that the localized electronic structure created by the active sites favors the protonation of adsorbed O2 and stabilizes the *OOH species, which converts to H2O2. This study elucidates and underscores the importance of active-site reconfiguration for efficient photocatalytic oxygen reduction reaction (ORR) pathways.

Probing local structure and electronic structure of α-Fe2O3/g-C3N4 S-scheme heterojunctions for boosting CO2 photoreduction

Construction of S-scheme heterojunction for photocatalytic conversion of CO2 into carbon-neutral fuels under sunlight is of paramount value for the sustainable development of energy. However, few reports are concerned the local structure and electronic structure of semiconductor heterojunction, which are importance of understanding the effect of heterojunction structure on the photocatalytic property. In this work, hierarchical α-Fe2O3/g-C3N4 S-scheme heterojunctions were manufactured via an in situ self-assembly strategy for the efficient reduction of CO2. The generation rate of main product CO for optimal α-Fe2O3/g-C3N4 heterojunction is up to 215.8 μmol g-1 h-1, with selectivity of 93.3 %, which is 17.5 and 6.1 times higher than those of pristine Fe2O3 and g-C3N4, respectively. The local structure and electronic structure for α-Fe2O3/g-C3N4 heterojunction are probed by hard X-Ray Absorption Fine Structure (XAFS) and soft X-Ray Absorption Spectroscopy (XAS), as well as density-functional theory (DFT) calculations. It is found that the Fe(d)-N(p) bond formed in α-Fe2O3/g-C3N4 heterojunction precisely connects the conduction band (CB) of Fe2O3 and the valence band (VB) of g-C3N4, which minimizes the charge transfer distance and facilitates CO2 photoreduction activity. This work provides important information for understanding the influence of interface local and electronic structure on the performance of photo-catalytic reduction of CO2 at the atomic level.

Asymmetric P-N3 bonds in polymeric carbon nitride: Polarizing localized charge for efficient photocatalytic hydrogen evolution and selective alcohol oxidation

The simultaneous generation of hydrogen (H2) and the oxidative transformation of organic molecules through photocatalytic processes represents a highly promising dual-purpose strategy. This approach obviates the necessity for sacrificial agents while augmenting catalytic efficiency, thereby facilitating the integrated production of high-value chemicals and renewable energy carriers. Polymeric carbon nitride (PCN) has emerged as a leading candidate among coupled photocatalysts. Nevertheless, PCN's efficacy is constrained by the inefficient separation of charges and the functional limitations of its active sites. Herein, the incorporation of P-N3 groups into PCN introduces active sites with pronounced charge asymmetry, resulting in strong local charge polarization. This asymmetric charge distribution, mediated by the P-N3 groups, significantly enhances exciton dissociation. Remarkably, the P-N3-modified narrow-dimensional fragmented carbon nitride (P-CNNS) achieves an 85 % conversion rate for 4-MBA with nearly 100 % selectivity, and a hydrogen evolution rate of 27.9 mmol g-1 (with Pt as a co-catalyst), representing 6.2 times higher than that of bulk carbon nitride (BCN). The charge-polarized sites facilitate the transfer of electrons, which is a pivotal process in the activation of 4-methoxybenzyl alcohol (4-MBA). Additionally, these sites serve as adsorption sites, facilitating the oxidation of 4-MBA into anisaldehyde (AA). This work underscores the potential of non-metallic site catalysts for a wide range of coupled photocatalytic applications.

Self-Assembled Perylenediimide Nanoaggregates with an Alternate Stringlike Morphology as Photoanodes to Enhance the H2O2 Photoelectrochemical Cell Performance

A self-assembled supramolecular photocatalyst of benzoic acid-substituted perylenediimide (SA-BAPDI) is successfully prepared, forming an alternate stringlike morphology driven by intermolecular hydrogen-bonding and π-π interactions. This unusual morphology induces a strong built-in electric field and an enormous π-conjugated effect, which can promote efficient separation of photogenerated carriers. Meanwhile, SA-BAPDI photocatalyst applied as the photoanode in the H2O2 photoelectrochemical cell for the first time can facilitate photocatalytic H2O2 production by water oxidation, which can be used as fuel to generate electricity through redox reactions and further to achieve solar-chemical-electrical energy conversion. The SA-BAPDI-based cell displays the maximum light power density of 1.06 mW·cm-2 and the specific capacitance of 5025 mF·cm-2 after 0.5 h of irradiation, which can still retain the original value of 50% in the dark for 12 h of continuous operation. This study verifies that morphology regulation of self-assembled perylenediimide supramolecular photocatalytic materials benefits the design and development of a high-performance H2O2 photoelectrochemical cell.

A bi-functional S-scheme cobalt-porphyrin conjugated polymer/C3N4 heterojunction for cooperative CO2 reduction and tetracycline degradation

The design of bifunctional photocatalysts for the removal of contaminants and the reduction of CO2 is of significant practical importance in addressing pollution and energy challenges. However, the photocatalytic efficiency is limited by the inadequate redox ability, high carrier recombination rate, and insufficient reactive sites of existing photocatalysts. Herein, a 2D/2D S-scheme heterojunction composed of cobalt-porphyrin conjugated polymer nanoflakes and C3N4 nanosheets (CoPor-DBE/CN) was rationally synthesized, exhibiting matched redox ability and favorable CO2 adsorption properties. The layered structure and functional groups of CoPor-DBE/CN provide numerous active sites, thereby enhancing the separation and transfer of charge carriers as well as the adsorption of reactants. Under visible light illumination, the optimized 50CoPor-DBE/CN hybrid achieved a CO production rate of 16.7 μmol g-1 h-1 and a tetracycline removal rate of 93.8%, which are significantly higher than those of the individual CN material. By employing X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and photo-irradiated Kelvin probe force microscopy (KPFM), we demonstrate that the transfer of charge carriers within the CoPor-DBE/CN system follows the S-scheme heterojunction mechanism. This work offers a promising blueprint for the design of multifunctional S-scheme photocatalysts aimed at the simultaneous efficient reduction of CO2 and degradation of organic pollutants.

Interfacial engineering of Co(OH)2@CN composites: A study of p-n heterojunctions with enhanced xylose/xylan photoreforming and CO2 reduction performance

The construction of p-n heterojunction is considered a prominent method for promoting efficient separation/migration of photoinduced carriers, thereby enhancing photocatalytic performance. Herein, a series of nanoflower spherical Co(OH)2@CN-x p-n heterojunction photocatalysts were fabricated using a simplified one-step hydrothermal strategy. Notably, Co(OH)2@CN-2 exhibited optimal performance, showcasing a carbon monoxide (CO) evolution rate of 46.2 μmol g-1 h-1 and a xylonic acid yield of 69.9 %. These values are 14.7/3.7 and 2.8/2.4 times higher than those of pristine CN and Co(OH)2, respectively. Additionally, Co(OH)2@CN-2 demonstrated excellent recyclability and chemical stability. Comparative experiments, coupled with 13CO2-labelling testing, confirmed the carbon sources of the obtained CO (72.3 % from CO2 reduction and 27.7 % from xylose oxidation). The charge transfer mechanism in Co(OH)2@CN-x p-n heterojunctions was systematically elucidated using in-situ X-ray photoelectron spectroscopy (in-situ XPS) and density functional theory (DFT) calculations. This work presents a practical approach for constructing p-n heterojunction photocatalysts to enhance photocatalytic biomass oxidation coupled with CO2 reduction.

Accelerated Water Oxidation Kinetics Induced by Oxygen Vacancies in the BiVO4/C3N4 S-Scheme Heterojunction for Enhanced Photocatalytic CO2 Reduction

The solar-driven photocatalytic reduction of CO2 into fuels using a C3N4-based photocatalyst has shown great application potential in addressing challenges related to energy and CO2 emission. However, this process suffers from severe charge recombination and sluggish H2O oxidation kinetics, resulting in low efficiency. In this study, a 2D/2D S-scheme heterojunction by combining oxygen vacancy-rich BiVO4 nanoflakes with C3N4 nanosheets (denoted as Ov-BVO/CN) was fabricated to mitigate the aforementioned issues, where BiVO4 serves as a water oxidation booster and C3N4 serves as the CO2 reduction center. By leveraging the synergistic effects of a lamellar morphology and an S-scheme charge-transfer pathway, the Ov-BVO/CN heterojunction achieves efficient charge separation while maintaining maximized redox capabilities. Moreover, theoretical calculations demonstrated that the Ov on the surface of BiVO4 reverses the rate-limiting step in H2O oxidation while reducing its energy barrier, thereby accelerating reaction kinetics. The optimized Ov-BVO/CN S-scheme heterojunction demonstrates remarkably improved photocatalytic evolution rates for CO (13.8 μmol g-1 h-1) and CH4 (5.9 μmol g-1 h-1), which are approximately 3.8 and 3.5 times higher than those of CN nanosheets under visible-light irradiation, respectively. This work highlights the design and fabrication of highly efficient heterostructure photocatalysts for CO2 photoreduction.

Precisely Tuning Band Gaps of Hexabenzocoronene-Based MOFs Toward Enhanced Photocatalysis

Precise adjusting the band gaps in metal-organic frameworks (MOFs) is crucial for improving their visible-light absorption capacity during photocatalysis, presenting both a formidable challenge and a charming opportunity. This present study employed a symmetry-reduction strategy to pre-design six novel 4-connected ligands with systematic substituents (-NO2, -H, -tBu, -OCH3, -OH and -NH2) and synthesized the corresponding pillared-layer Zr-MOFs (NKM-668) retaining the hexaphenylbenzene fragment. Subsequently, the NKM-668 MOFs were transformed into large-π-conjugated hexabenzocoronene-based MOFs (pNKM-668) via the Scholl reaction. These twelve MOFs exhibited broad and tunable band gaps over 1.41 eV (ranging from 3.25 eV to 1.84 eV), and the photocatalytic CO2 conversion rate raised by 33.2-fold. This study not only enriches the type of hexaphenylbenzene-based MOFs, but also paves the way for nanographene-containing MOFs in the further application of photocatalysis.

Mild-Condition Photocatalytic Reforming of Methanol-Water by a Hierarchical, Asymmetry Carbon Nitride

As a reproducible intermediate for hydrogen (H2) and carbon cycling, methanol mixed with water (H2O) in a ratio of 1 : 1 can multiply the outcome of green H2 generation via Photocatalytic reforming of methanol-H2O (PRMW). Hitherto, low-energy and mild-condition PRMW remains a serious challenge. Here, the amino acid-derived carbon nitrides (ACN) were synthesized supramolecular precursor strategy for PRMW and achieved excellent performance (H2, 35.6 mmol h-1 g-1; CO2, 11.5 mmol h-1 g-1) under sunlight at 35 °C. It was revealed that the surface-terminating carboxyl groups (-COOH) promote the dark dehydrogenation of methanol on MetCNx to form methoxy (*OCH3) and methylol (*CH2OH) simultaneously, with the hydroxyl (*OH) generated by photostimulated H2O oxidation promotes the C-H activation of formaldehyde, then leads the whole reaction into the formation of CO2 and three H2. The extended light absorption, enhanced charge separation and transport, and efficient surface reaction improve photocatalytic efficiency.

Nanoarchitectonics of vanadium nanoparticles decorated mesoporous carbon nitride in photocatalytic systems: A study on ethylbenzene oxidation reaction

In this work, we have described the synthesis of vanadium (V) nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (V@mpg-C3N4) and their uses in photocatalytic ethylbenzene oxidation to the respective acetophenones. The mpg-C3N4 serves as the support for the decoration of V NPs, through a simple impregnation method. Various advanced techniques, such as XRD, UV-vis spectrometry, HRTEM, HAADF-STEM, AC-STEM, elemental mapping, and BET surface area analysis, were employed for the characterization of V@mpg-C3N4. The detailed characterization studies reveal that the V@mpg-C3N4 catalyst has a medium band gap (2.78 eV), a high surface area (76.7 m2g-1), and a mesoporous nature. The V@mpg-C3N4 photocatalysts demonstrated excellent performance in the light-assisted oxidation of ethylbenzene, achieving over 99 % conversion and selectivity for acetophenone in an environmentally friendly solvent (water) using a domestic light source (50 W white light). This developed synthesis strategy will be useful for synthesizing various noble and non-noble metal-based catalysts and their applications in organic transformation and environmental remediation.

Engineering Planar Crystallinity in Nitrogen-Vacancy-Incorporated Carbon Nitride for Efficient Photoredox Catalysis

The concurrent evolution of value-added benzimidazole compounds and hydrogen within the domain of chemical synthesis is of paramount importance. The utilization of photocatalysis enhances both the efficiency and environmental benignity of the synthetic process. However, it is profoundly challenging within a photocatalytic system to simultaneously augment the number of active sites and the internal transport rate of photogenerated charge carriers. To address this issue, a template-free, step-by-step assembly strategy has been proposed for the synthesis of planar crystalline carbon nitride (CCN) incorporated with a nitrogen vacancy (Nv). In contrast to the simultaneous assembly method, the sequential assembly process encompasses a progressive crystallization mechanism. This method is conducive to the mitigation of the incidence of structural disarray, thereby precluding the genesis of non-ordered defects throughout the whole bulk phase. The ordered in-plane arrangement facilitates the spatial segregation of electrons and holes, thereby decoupling the redox active sites. This separation minimizes the likelihood of back reactions and suppresses the recombination process, which is advantageous for the efficiency of photocatalytic coupling reactions. Certified by multiscale characterization and theoretical simulations, the incorporation of Nv enhances the energy band structure and provides sites with unsaturated coordination for the adsorption and activation of ethanol molecules. This interfacial synergistic effect of Nv and co-catalyst Pt as the Lewis site achieves efficient activation of both coupling partners. The obtained CCN demonstrates significant bifunctional photocatalytic activity, achieving a yield of benzimidazole at 5.0 mmol g-1 with a conversion and selectivity rate of 99%. Simultaneously, the hydrogen evolution rate of CCN is measured at 9.1 mmol g-1 within 4 h. The template-free, step-by-step assembled strategy utilized in this study provides new perspectives on developing highly efficient photocatalysts at the molecular level.

Engineered Polymeric Carbon Nitride for Photocatalytic Diverse Functionalization of Electronic-Rich Alkenes

Engineered polymeric carbon nitride represents a promising class of metal-free semiconductor photocatalysts for organic synthesis. Herein, we utilized engineered polymeric carbon nitride nanosheets, which exhibit an increased specific surface area and band gap due to enhanced quantum confinement from vacancy enrichment. These nanosheets serve as a heterogeneous organic semiconductor photocatalyst to facilitate diverse functionalizations of electron-rich alkenes, including arylsulfonylation, aminodifluoroalkylation, and oxytrifluoromethylation. This catalytic system operates under mild conditions, offering excellent functional group compatibility and high yields. Additionally, the catalyst demonstrates outstanding recyclability and efficiency in flow reactors, highlighting its significant potential for industrial applications.

Imine Synthesis by Engineered d-Amino Acid Oxidase from Porcine Kidney

Various symmetric and asymmetric imines were synthesized using the novel amine oxidase, obtained as variants of d-amino acid oxidase (pkDAO) from porcine kidney (Y228L/R283G) and (I230A/R283G). Active primary imines produced as intermediates in the oxidation of methylbenzylamine (MBA) derivatives were trapped by aliphatic, aromatic amines and diamines as nucleophiles forming new imines. (R)-Fluoro-MBA was the best substrate for symmetric imine synthesis, providing almost stoichiometric conversion (100 mM) and achieving nearly 100% yield. Several (R)-MBA derivatives were used as substrates, and the corresponding symmetric and asymmetric imines were synthesized. The turnover number of N-benzylidenebenzylamine synthesis from benzylamine was calculated to be 1.61 × 105 (number of moles of reactant consumed per mole of catalyst/h), which is more than 103 higher than metal-, photo-, and organo-catalysts reported so far. The diastereomers of bis(1-phenylethyl)amine, the reduced products of (R)-MBA, were identified as a mixture of 84.9% (R,R)-bis(1-phenylethyl)amine and 15.1% (R,S)-bis(1-phenylethyl)amine to consider the reaction mechanism.

Fragmented Polymetric Carbon Nitride with Rich Defects for Boosting Electrochemical Synthesis of Hydrogen Peroxide in Alkaline and Neutral Media

Electrocatalytic oxygen reduction reaction via 2e- pathway is a safe and friendly route for hydrogen peroxide (H2O2) synthesis. In order to achieve efficient synthesis of H2O2, it is essential to accurately control the active sites. Here, fragmented polymetric carbon nitride with rich defects (DCN) is designed for H2O2 electrosynthesis. The multi-type defects, including the sodium atom doping in six-fold cavities, the boron atom doping at N-B-N sites and the cyano groups, are successfully created. Owing to the synergistic effect of these defects, the fragmented DCN achieves a high H2O2 production rate of 2.28 mol gcat. -1 h-1 and a high Faradic efficiency of nearly 90 % in alkaline media at 0.4 V vs. RHE in H-type cell. In neutral media, the H2O2 concentration produced by DCN can reach 1815 μM within 6 h at a potential of 0.2 V vs. RHE, and the H2O2 production rate of DCN is 0.23 mol gcat. -1 h-1. In addition, DCN shows excellent long-term durability in alkaline and neutral media. This study provides a new approach for the development of the boron, nitrogen doped carbon-based electrocatalysts for H2O2 electrochemical synthesis.

Oxygen-Doped Porous Ultrathin Graphitic Carbon Nitride Nanosheets for Photocatalytic Hydrogen Evolution and Rhodamine B Degradation

Graphite phase carbon nitride (g-C3N4) is a highly promising metal-free photocatalyst, but its low activity, due to limited quantum efficiency and small specific surface area, restricts its practical application. While exfoliating bulk crystals into porous thin-layer nanosheets and incorporating dopants have been shown to improve photocatalytic efficiency, these methods are typically complex, time-consuming, and costly processes. In this study, we developed a simple approach to synthesize oxygen-doped porous g-C3N4 (OCN) nanosheets. The resulting OCN exhibited significantly enhanced light absorption and visible-light photocatalytic activity compared to bulk g-C3N4 (BCN) and g-C3N4 (CN). The OCN achieved an impressive hydrogen evolution reaction (HER) rate of 8.02 mmol g-1 h-1, eight times greater than BCN, and demonstrated a high Rhodamine B (RhB) degradation rate of 97.3 % owing to the generation of abundant singlet oxygen. These improvements in photocatalytic performance are attributed to the narrow band gap and enhanced electron transfer properties, suggesting a promising route for the efficient design of g-C3N4-based photocatalysts.

Ru Metalloligands Participate in the Construction of POM@MOF for Enhancing the Visible Photoinduced Baeyer-Villiger Oxidation Reaction

Directed synthesis of high-efficiency visible photoinduced Baeyer-Villiger oxidation catalysts is of primary significance. Here, the isopolymolybdate anion [β-Mo8O26]4- is for the first time encapsulated with the photosensitive metalloligand [Ru(bpy)2(H2dcbpy)]2+ (bpy = 2,2'-bipyridine; H2dcbpy = 2,2'-bipyridine-5,5'-dicarboxylic acid) to synthesize polyoxometalate@metal-organic frameworks, {(CdDMF)2[Ru(bpy)2(dcbpy)]3([β-Mo8O26])}·5DMF (Ru-Mo8). The composite photocatalyst Ru-Mo8 not only has a light absorption of 700 nm but also shortens the photogenerated electron transfer distances and accelerates charge and proton transfer. Ru-Mo8 can perform the Baeyer-Villiger oxidation with high selectivity and up to 96.7% yield under visible light (λ > 400 nm) irradiation. The turnover number and turnover frequency of the reaction were computed to be 967 and 548 h-1, respectively, and the apparent quantum yield was 6.84% by 425 nm. Simultaneously, the radical mechanism of Baeyer-Villiger oxidation of Ru-Mo8 in the O2/benzaldehyde system under visible light (λ > 400 nm) irradiation was proposed.

Reinforcing the Efficiency of Plastic Upgrading through Full-Spectrum Photothermal Effect Integration of Heat Isolator

Photoreforming of polyethylene terephthalate (PET) to H2 is practically attractive strategy for upgrading waste plastics. The major challenge is to utilize the infrared energy in the solar spectrum to improve the efficiency for photoreforming of PET to H2. Herein, through the ingenious integration of tungsten phosphide nanoparticles and tungsten single atoms (WP/W SAs) with carbon nitride (g-C3N4), the constructed hybrid inherits both the desirable properties and structural merits of the respective building blocks. Specifically, the photothermal effect of WP/W SAs couples with the "heat isolator" role of g-C3N4 due to its low thermal conductivity, thereby forming localized high-temperature regions, reducing the activation energy and improving the kinetics in the photoreforming of PET to H2. Additionally, the green pretreatment of PET using alkali-free hydrothermal strategy is reported, achieving direct separation of the ethylene glycol and terephthalic acid. This work not only provides an alkali-free hydrothermal pretreatment for PET, but also integrates the photothermal effect with the thermal insulation and opens a new avenue for harnessing solar energy into to convert plastics into H2.

Photoinduced Zn-Air Battery-Assisted Self-Powered Sensor Utilizing Cobalt and Sulfur Co-Doped Carbon Nitride for Portable Detection Device

Most self-powered electrochemical sensors (SPESs) are limited by low open circuit voltage and power density, leading to a narrow detection range and low sensitivity. Herein, a photoinduced Zn-air battery-assisted SPES (ZAB-SPES) is proposed based on cobalt and sulfur co-doped carbon nitride with the cyano group (Co, S-CN). The cyano functionalization remarkably enhances visible light utilization, and the cyano moiety acts as an electron-withdrawing group to promote electron enrichment. Co and S co-doping can create a p-n homojunction within carbon nitride, enabling the efficient migration and separation of carriers, thereby significantly improving the performance of the oxygen reduction reaction. The synergistic effects endow Co, S-CN photocathode with an open circuit voltage of 1.85 V and the maximum power density of 43.5 µW cm-2 in the photoinduced ZAB. Employing heavy metal copper ions as the target model, the photoinduced ZAB-SPES exhibited dual-mode and sensitive detection. Furthermore, a portable detection device based on the photoinduced ZAB-SPES is designed and exhibits high linearity in the range of 5 ~ 600 nM with a detection limit of 1.7 nM. This work offers a portable detection method based on the photoinduced ZAB-SPES in the aquatic environment.

Photoinduced Deoxygenative C2 Arylation of Quinoline N-oxides with Phenylhydrazines to 2-Arylquinolines over Porous Tubular Graphitic Carbon Nitride Semiconductor Photocatalyst

The photo-induced deoxygenative C2 arylation of quinoline N-oxides to 2-arylquinolines is achieved over a heterogeneous porous tubular graphitic carbon nitride (PTCN) catalyst with phenylhydrazines as arylation reagent. A wide range of quinoline N-oxides can be efficiently transformed into their corresponding 2-arylquinolines under visible light irradiation. Moreover, PTCN catalyst is easily separated and could be reused several times without loss to its original activity.

Strategy for Highly Efficient Detection and Removal of Raman Inactive Leuco-Malachite Green on Environmentally Friendly Graphitic Carbon Nitride-Based Nanostructures

The sustainable identification and efficient degradation of some recessive and seriously toxic pollutants are important issues in practical applications. Herein, a portable platform (EAl/ACN/Ag) constructed by growing AgNPs in situ in the cavities of the alkalized carbon nitride (ACN) coated on the etched Al sheet (EAl) is achieved. Interestingly, on the constructed EAl/ACN/Ag substrate irradiated by light for 3 min, a Raman inactive leuco-malachite green (LMG: a highly toxic and environmentally persistent pollutant that is difficult to be found due to being colorless) can be sensitively and selectively detected by surface-enhanced Raman scattering spectroscopy (SERS). Results demonstrate that the abundant •O2-, •OH, and h+ active species produced by irradiation of the EAl/ACN/Ag are responsible for the sensitive and selective SERS detection of the Raman-inactive LMG. The green and sustainable initiation in the sensitive SERS detection of LMG is greatly different from those by the traditional chemical process. The limit of detection of LMG can reach 8.99 × 10-13 mol·L-1, which is superior to some other methods for LMG detection in real samples. In addition, the EAl/ACN/Ag substrate displays excellent photocatalytic activity for LMG molecules. The research will provide a new and green way for the sensitive detection and efficient removal of some recessive and toxic pollutants in food fields and environmental analyses.

Graphitic Carbon Nitride Structures on Carbon Cloth Containing Ultra- and Nano-Dispersed NiO for Photoactivated Oxygen Evolution

The development of low-cost and high-efficiency oxygen evolution reaction (OER) photoelectrocatalysts is a key requirement for H2 generation via solar-assisted water splitting. In this study, we report on an amenable fabrication route to carbon cloth-supported graphitic carbon nitride (gCN) nanoarchitectures, featuring a modular dispersion of NiO as co-catalyst. The synergistic interaction between gCN and NiO, along with the tailoring of their size and spatial distribution, yield very attractive OER performances and durability in freshwater splitting, of great significance for practical end-uses. The potential of gCN electrocatalysts containing ultra-dispersed, i. e. "quasi-atomic" NiO, exhibiting a higher activity than the ones containing nickel oxide nanoaggregates, is further highlighted by their activity even in real seawater. This work suggests that efficient OER catalysts can be designed through the construction of optimized interfaces between transition metal oxides and carbon nitride, yielding inexpensive and promising noble metal-free systems for real-world applications.

Synergistic Modulation of π-π* and n-π* Transitions by In Situ Phenol-Like Structure Integration for Efficiently Wide-Spectrum Hydrogen Production of Ultrathin Carbon Nitride

2D carbon nitride nanosheets, exemplified by g-C3N4, offers significant structural benefits and enhanced photocatalytic activity. Nonetheless, the quantum confinement effect prevalent in nanoscale photocatalysts would result in an enlarged bandgap, potentially restricting the spectral absorption range and impeding improvements in photocatalytic efficiency. Here, a high-performance 2D photocatalyst with an extended spectral response is achieved by incorporating a novel phenol-like structure into the conjugated framework of ultrathin g-C3N4 nanosheet. This novel strategy features targeted pyrimidine doping to create a conjugated carbon zone in heptazine structure, offering a thermodynamically favorable pathway for hydroxyl functionalization during the annealing exfoliation process. Consequently, the π-π* transition energy in the material is significantly decreased, and the active lone pair electrons in phenol-like structure induces a new n-π* transition with notably enhanced absorption from 500 to 650 nm. The optimized material shows a dramatic enhancement in photocatalytic activity, achieving ≈72 times than the activity of bulk g-C3N4, and demonstrating a measurable H2 production rate of 6.57 µmol g-1 h-1 under 650 nm light. This study represents a significant step forward in the strategic design of 2D photocatalysts, with tailored electronic structures that significantly boost light absorption and photocatalytic efficiency.

Cs3Bi2Br9 nanoparticles decorated C3N4 nanotubes composite photocatalyst for highly selective oxidation of benzylic alcohol

Solar-light driven oxidation of benzylic alcohols over photocatalysts endows significant prospects in value-added organics evolution owing to its facile, inexpensive and sustainable process. However, the unsatisfactory performance of actual photocatalysts due to the inefficient charge separation, low photoredox potential and sluggish surface reaction impedes the practical application of this process. Herein, we developed an innovative Z-Scheme Cs3BiBr9 nanoparticles@porous C3N4 tubes (CBB-NP@P-tube-CN) heterojunction photocatalyst for highly selective benzyl alcohol oxidation. Such composite combining increased photo-oxidation potential, Z-Scheme charge migration route as well as the structural advantages of porous tubular C3N4 ensures the accelerated mass and ions diffusion kinetics, the fast photoinduced carriers dissociation and sufficient photoredox potentials. The CBB-NP@P-tube-CN photocatalyst demonstrates an exceptional performance for selective photo-oxidation of benzylic alcohol into benzaldehyde with 19, 14 and 3 times higher benzylic alcohols conversion rate than those of C3N4 nanotubes, Cs3Bi2Br9 and Cs3Bi2Br9@bulk C3N4 photocatalysts, respectively. This work offers a sustainable photocatalytic system based on lead-free halide perovskite toward large scale solar-light driven value-added chemicals production.

Energy transfer-mediated multiphoton synergistic excitation for selective C(sp3)-H functionalization with coordination polymer

Activation and selective oxidation of inert C(sp3)-H bonds remain one of the most challenging tasks in current synthetic chemistry due to the inherent inertness of C(sp3)-H bonds. In this study, inspired by natural monooxygenases, we developed a coordination polymer with naphthalenediimide (NDI)-based ligands and binuclear iron nodes. The mixed-valence FeIIIFeII species and chlorine radicals (Cl•) are generated via ligand-to-metal charge transfer (LMCT) between FeIII and chlorine ions. These Cl• radicals abstract a hydrogen atom from the inert C(sp3)-H bond of alkanes via hydrogen atom transfer (HAT). In addition, NDI converts oxygen to 1O2 via energy transfer (EnT), which then coordinates to FeII, forming an FeIV = O intermediate for the selective oxidation of C(sp3)-H bonds. This synthetic platform, which combines photoinduced EnT, LMCT and HAT, provides a EnT-mediated parallel multiphoton excitation strategy with kinetic synergy effect for selective C(sp3)-H oxidation under mild conditions and a blueprint for designing coordination polymer-based photocatalysts for C(sp3)-H bond oxidation.

Graphitic Carbon Nitride as a Promising Visible-Light-Activated Support Boosting Platinum Nanoparticle Activity in Ethanol Electrooxidation

In the present work, exfoliated graphitic carbon nitride (g-CN) is immobilized on carbon paper substrates by a simple electrophoretic route, and subsequently decorated with ultra-low amounts (≈μg/cm2) of Pt nanoparticles (NPs) by cold plasma sputtering. Optimization of preparative conditions allowed a fine tuning of Pt NPs size, loading and distribution and thus a controlled tailoring of g-CN/Pt interfacial interactions. Modulation of such features yielded g-CN-Pt-based anode materials with appealing activity and stability towards the ethanol oxidation reaction (EOR) in alkaline aqueous solutions, as revealed by electrochemical tests both in the dark and under irradiation. The present results provide new insights on the design of nano-engineered heterocomposites featuring improved performances thanks to Pt coupling with g-CN, a low-cost and environmentally friendly visible light-active semiconductor. Overall, this work might open attractive avenues for the generation of green hydrogen via aqueous ethanol electrolysis and the photo-promoted alcohol electrooxidation in fuel cells.

Modulating Copper Ladder Spacing in Copper Phenylacetylide for Enhanced Photocatalysis via Substituent Control

Copper phenylacetylide (PACu) is a promising photocatalyst due to its unique copper ladder (CL) electron transport channel, which facilitates efficient charge transfer. However, the structure-activity relationship between the CL spacing and its catalytic performance has yet to be revealed. In this study, we skillfully selected multiple substituents to regulate the CL spacing of the PACu photocatalyst. Our findings indicate that reducing the CL spacing significantly enhances carrier separation and transport efficiency, leading to improved oxygen adsorption and activation. Specifically, PACu-F demonstrated superior photocatalytic activity, achieving a 99% conversion rate in benzylamine oxidation and maintaining an excellent stability over multiple cycles. This study confirms the feasibility of tuning the CL spacing in PACu using donor/acceptor substituents to achieve a high-efficiency photocatalytic performance, offering crucial insights into the rational design of advanced photocatalysts.

Recent advances and perspectives on intercalation layered compounds part 1: design and applications in the field of energy

Herein, initially, we present a general overview of the global financial support for chemistry devoted to materials science, specifically intercalation layered compounds (ILCs). Subsequently, the strategies to synthesise these host structures and the corresponding guest-host hybrid assemblies are exemplified on the basis of some families of materials, including pillared clays (PILCs), porous clay heterostructures (PCHs), zirconium phosphate (ZrP), layered double hydroxides (LDHs), graphite intercalation compounds (GICs), graphene-based materials, and MXenes. Additionally, a non-exhaustive survey on their possible application in the field of energy through electrochemical storage, mostly as electrode materials but also as electrolyte additives, is presented, including lithium technologies based on lithium ion batteries (LIBs), and beyond LiBs with a focus on possible alternatives such XIBs (X = Na (NIB), K (KIB), Al (AIB), Zn (ZIB), and Cl (CIB)), reversible Mg batteries (RMBs), dual-ion batteries (DIBs), Zn-air and Zn-sulphur batteries and supercapacitors as well as their relevance in other fields related to (opto)electronics. This selective panorama should help readers better understand the reason why ILCs are expected to meet the challenge of tomorrow as electrode materials.

Construction of Frustrated Lewis Pairs in Poly(heptazine Imide) Nanosheets via Hydrogen Bonds for Boosting CO2 Photoreduction

The creation of frustrated Lewis pairs on catalyst surface is an effective strategy for tuning CO2 activation. The critical step in the formation of frustrated Lewis pairs is the spatial effect of proximal Lewis acid-Lewis base pairs. Here, we demonstrate a facile surface functionalization methodology that enables hydrogen bonding between N and H atoms to mediate the construction of frustrated Lewis pairs in poly(heptazine imide), thereby increasing the propensity to activate CO2 molecules. Experimental and theoretical results show that the construction of active hydrogen bonding regions can facilitate the bending of CO2 molecules. Furthermore, the delocalization of electron clouds induced by the hydrogen bonding-mediated frustrated Lewis pairs can promote the heterolytic cleavage and photocatalytic conversion of CO2. This work highlights the potential of utilizing hydrogen bonding-mediated strategy in heterogeneously photocatalytic activation of CO2 over polymer materials.

Strategies for improving photocatalytic performance of g-C3N4 by modulating charge separation and current research status

Graphitic carbon nitride (g-C3N4) has been extensively investigated over the past decade for its potential utilizations in photocatalytic energy generation and pollutant degradation. To better meeting the requirements for practical utilizations, it is crucial to address the issue of poor charge separation properties in g-C3N4, which origin from the strong interactions in photogenerated electron-hole pairs. In this review, we summarized the pertinent studies on developing strategies to promote the charge separation properties of g-C3N4. The strategies can be categorized into two categories of promoting the surface migration of charge carriers and prolonging the lifetime of surface charge. Finally, we present potential challenges in promoting charge separation and offer feasible suggestions to face these challenges.

A novel photoelectrochemical aptasensor based on 3D flower-like g-C3N4/BiOI p-n heterojunction for the sensitive detection of kanamycin

BACKGROUND

Kanamycin (KAN) residues in animal-derived foods continuously enter the human body, which will pose serious threats to human health such as hearing loss, nephrotoxicity and other complications. Therefore, to sensitively detect KAN residues by a reliable technology is extremely urgent in food quality and safety. Compared with traditional methods being limited by cost and complexity, photoelectrochemical (PEC) biosensors benefit from some merits such as rapid response, excellent sensitivity and good stability. In this study, the construction of a highly efficient PEC platform to realize KAN residues detection is discussed.

RESULTS

Herein, a novel p-n heterojunction consisting of flower-like BiOI microspheres and graphite carbon nitride (g-C3N4) nanoflakes was developed to establish a PEC aptasensor for KAN detection at 0 V. The prepared g-C3N4/BiOI heterostructure showed not only significantly enhanced PEC activity due to the larger specific surface area but also greatly increased charge separation efficiency owing to the strong internal electric field. Meanwhile, using g-C3N4/BiOI as a highly efficient photoactive material for binding amine-functionalized aptamers to capture KAN, the photocurrent signals showed a 'turn off' mode to achieve the sensitive detection of KAN. The proposed PEC aptasensor exhibited linear response for KAN from 5 × 10-9 to 3 × 10-7 mol L-1 with a low detection limit of 1.31 × 10-9 mol L-1, and satisfactory recoveries (97.44-107.38 %) were obtained in real food samples analysis.

SIGNIFICANCE

This work presented a novel p-n heterojunction-based PEC aptasensor with strong selectivity and stability, rendering it allowed to detect KAN in animal-derived foods including milk, honey and pork. Additionally, the detection range satisfied the MRLs for KAN specified by the national standards, demonstrating the potential application for food analysis. The study provides a new insight into the development of efficient and practical biosensors for antibiotic residues detection.

Photocatalytic Reduction of Perrhenate and Pertechnetate in a Strongly Acidic Aqueous Solution

Pertechnetate (99TcO4-), a physiologically toxic radioactive anion, is of great concern due to its high mobility in environmental contamination remediation. Although the soluble oxyanion can be photoreduced to sparingly soluble TcO2·nH2O, its effective removal from a strongly acidic aqueous solution remains a challenge. Here, we found that low-crystalline nitrogen-doped titanium oxide (N-TiO2, 0.6 g L-1) could effectively uptake perrhenate (ReO4-, 10 mg L-1, a nonradioactive surrogate for TcO4-) with 50.8% during 360 min under simulated sunlight irradiation at pH 1.0, but P25 and anatase could not. The nitrogen active center formed by trace nitrogen doping in N-TiO2 can promote the separation and transfer of photogenerated carriers. The positive valence band value of N-TiO2 is slightly higher than those of P25 and anatase, which means that the photogenerated holes have a stronger oxidizability. These holes are involved in the formation of strong reducing •CO2- radicals from formic acid oxidation. The active radicals convert ReO4- to Re(VI), which is subsequently disproportionated to Re(IV) and Re(VII). Effective photocatalytic reduction/removal of Re(VII)/Tc(VII) is performed on the material, which may be considered a potential and convenient strategy for technetium decontamination and extraction in a strongly acidic aqueous solution.

Creation of Interfacial S4-Sn-N2 Electron Pathways for Efficient Light-Driven Hydrogen Evolution

Establishing effective charge transfer channels between two semiconductors is key to improving photocatalytic activity. However, controlling hetero-structures in situ and designing binding modes pose significant challenges. Herein, hydrolytic SnCl2·2H2O is selected as the metal source and loaded in situ onto a layered carbon nitriden supramolecular precursor. A composite photocatalyst, S4-Sn-N2, with electron pathways of SnS2 and tubular carbon nitriden (TCN) is prepared through pyrolysis and vulcanization processes. The contact interface of SnS2-TCN is increased significantly, promoting the formation of S4-Sn-N2 micro-structure in a Z-scheme charge transfer channel. This structure accelerates the separation and transport of photogenerated carriers, maintains the stronger redox ability, and improves the stability of SnS2 in this series of heterojunctions. Therefore, the catalyst demonstrated exceptional photocatalytic hydrogen production efficiency, achieving a reaction rate of 86.4 µmol h-1, which is 3.15 times greater than that of bare TCN.

Preparation of a Nanosheeted Uranyl-Organic Framework for Enhanced Photocatalytic Oxidation of Toluene

Preparation of ultrathin metal-organic framework (MOF) nanosheets is an effective way to improve the catalytic efficiency of MOF photocatalysts owing to their superiority in reducing the recombination rate of photogenerated electrons and holes and enhancing charge transfer. Herein, a light-sensitive two-dimensional uranyl-organic framework named HNU-68 was synthesized. Due to its interlayer stacking structure, the corresponding ultrathin nanosheets with a thickness of 4.4 nm (HNU-68-N) can be obtained through ultrasonic exfoliation. HNU-68-N exhibited an enhanced ability to selectively oxidize toluene to benzaldehyde, with the value of turnover frequency being approximately three times higher than that of the bulk HNU-68. This enhancement is attributed to the smaller size and interface resistance of the layered HNU-68-N nanosheets, which facilitate more thorough substrate contact and faster charge transfer, leading to an improvement in the photocatalytic efficiency. This work provides a potential candidate for the application of ultrathin uranyl-based nanosheets.

Schottky Junction Enhanced Photosynthesis of Hydrogen Peroxide by Ultrathin Porous Carbon Nitride Supported Ni Nanoparticles

Artificial photosynthesis for high-value hydrogen peroxide (H2O2) through a two-electron reduction reaction is a green and sustainable strategy. However, the development of highly active H2O2 photocatalysts is impeded by severe carrier recombination, ineffective active sites, and low surface reaction efficiency. We developed a dual optimization strategy to load dense Ni nanoparticles onto ultrathin porous graphitic carbon nitride (Ni-UPGCN). In the absence and presence of sacrificial agents, Ni-UPGCN achieved H2O2 production rates of 169 and 4116 μmol g-1 h-1 with AQY (apparent quantum efficiency) at 420 nm of 3.14% and 17.71%. Forming a Schottky junction, the surface-modified Ni nanoparticles broaden the light absorption boundary and facilitate charge separation, which act as active sites, promoting O2 adsorption and reducing the formation energy of *OOH (reaction intermediate). This results in a substantial improvement in both H2O2 generation activity and selectivity. The Schottky junction of dual modulation strategy provides novel insights into the advancement of highly effective photocatalytic agents for the photosynthesis of H2O2.

Tailored Exfoliation of Polymeric Carbon Nitride for Photocatalytic H2O2 Production and CH4 Valorization Mediated by O2 Activation

The exfoliation of bulk C3N4 (BCN) into ultrathin layered structure is an effective strategy to boost photocatalytic efficiency by exposing interior active sites and accelerating charge separation and transportation. Herein, we report a novel nitrate anion intercalation-decomposition (NID) strategy that is effective in peeling off BCN into few-layer C3N4 (fl-CN) with tailored thickness down to bi-layer. This strategy only involves hydrothermal treatment of BCN in diluted HNO3 aqueous solution, followed by pyrolysis at various temperatures. The decomposition of the nitrate anions not only exfoliates BCN and changes the band structure, but also incorporates oxygen species onto fl-CN, which is conducive to O2 adsorption and hence relevant chemical processes. In photocatalytic O2 reduction under visible light irradiation, the H2O2 production rate over the optimal fl-CN-530 catalyst is 952 μmol g-1 h-1, which is 8.8 times that over BCN. More importantly, under full arc irradiation and in the absence of hole scavenger, CH4 can be photocatalytically oxidized by on-site formed H2O2 and active oxygen species to generate value-added C1 oxygenates with high selectivity of 99.2 % and record-high production rate of 1893 μmol g-1 h-1 among the metal-free C3N4-based photocatalysts.

Effective oxygen activation on polyoxometalate-based hybrids for epoxidation of alkenes

Two polyoxometalate-based hybrids, [M(btap)3(H2O)3(HPW12O40)]·xH2O (M-PW, M = Co/Mn, btap = 3,5-bis(1',2',4'-triazol-1'-yl)pyridine) were synthesized. Co-PW exhibited higher activity and selectivity towards olefin epoxidation than Mn-PW due to the synergistic effect between CoII and PW, in which the Co centers activate O2 to ˙O2- and further binding of free H+ from PW affords the active peroxyacid.

Carbon Dots Anchoring Single-Atom Pt on C3N4 Boosting Photocatalytic Hydrogen Evolution

Carbon nitride (C3N4) has gained considerable attention and has been regarded as an ideal candidate for photocatalytic hydrogen evolution. However, its photocatalytic efficiency is still unsatisfactory due to the rapid recombination rate of photo-generated carriers and restricted surface area with few active sites. Herein, we successfully synthesized a single-atom Pt cocatalyst-loaded photocatalyst by utilizing the anchoring effect of carbon dots (CDs) on C3N4. The introduction of CDs onto the porous C3N4 matrix can greatly enhance the specific surface area of C3N4 to provide more surface-active sites, increase light absorption capabilities, as well as improve the charge separation efficiency. Notably, the functional groups of CDs can efficiently anchor the single-atom Pt, thus improving the atomic utilization efficiency of Pt cocatalysts. A strong interaction is formed via the connection of Pt-N bonds, which enhances the efficiency of photogenerated electron separation. This unique structure remarkably improves its H2 evolution performance under visible light irradiation with a rate of 15.09 mmol h-1 g-1. This work provides a new approach to constructing efficient photocatalysts by using CDs for sustainable hydrogen generation, offering a practical approach to utilizing solar energy for clean fuel production.

Strategic Insertion of Heavy Atom to Tailor TADF OLED Material for the Development of Type I Photosensitizing Catalytic Red Emissive Assemblies

The work presented in the manuscript describes a simple strategy for transforming thermally activated delayed fluorescent organic light-emitting diodes (TADF OLEDs) compound 10-(dibenzo[a,c]phenazin-11-yl)-10H-phenoxazine (DPZ-PXZ) into type I photosensitizer 10-(dibenzo[a,c]phenazin-11-yl)-10H-phenothiazine (DPZ-PHZ) by strategically introducing sulfur atom in the photosensitizing core. The synthesized compound DPZ-PHZ exhibits aggregation-induced enhancement (AIE) and through-space charge transfer (TSCT) characteristics and generates red emissive assemblies in mixed aqueous media. The original compound DPZ-PXZ exhibits well-separated HOMO and LUMO levels and is reported to have highly efficient reverse intersystem crossing (RISC). In comparison, the incorporation of sulfur atom in the phenothiazine donor regulates the electronic communication between donor and acceptor units and promotes the intersystem crossing (ISC) in DPZ-PHZ molecules. Interestingly, compound DPZ-PHZ exhibits rapid activation of aerial oxygen for instant generation of superoxide radical anion. Backed by excellent type I photosensitizing activity, DPZ-PHZ assemblies have high catalytic potential for the synthesis of benzimidazoles, benzothiazoles and quinazolines derivatives under mild reaction conditions. The work presented in the manuscript provides an insight into the combination of heavy atom approach and TSCT for achieving adequate electronic communication between donor and acceptor units, balanced RISC/ISC, and stabilized-charge separated state for the development of efficient type I photosensitizing assemblies.

Preparation of highly dispersed Ni single-atom doped ultrathin g-C3N4 nanosheets by metal vapor exfoliation for efficient photocatalytic CO2 reduction

Single-atom photocatalysts can modulate the utilization of photons and facilitate the migration of photogenerated carriers. However, the preparation of single-atom uniformly doped photocatalysts is still a challenging topic. Herein, we propose the preparation of Ni single-atom doped g-C3N4 photocatalysts by metal vapor exfoliation. The Ni vapor produced by calcining nickel foam at high temperature accumulates in between g-C3N4 layers and poses a certain vapor pressure to destroy the interlayer van der Waals forces of g-C3N4. Individual metal atoms are doped into the structure while exfoliating g-C3N4 into nanosheets by metal vapor. Upon optimization of Ni content, the Ni single atom doped g-C3N4 nanosheets with 2.81 wt% Ni exhibits the highest CO2 reduction performance in the absence of sacrificial agents. The generation rates of CO and CH4 are 19.85 and 1.73 μmol g-1h-1, respectively. The improved photocatalytic performance is attributed to the anchoring Ni of single atoms on g-C3N4 nanosheets, which increases both carrier separation efficiency and reaction sites. This work provides insight into the design of photocatalysts with highly dispersed single-atom.

Template-Free Synthesis of Boron-Doped Graphitic Carbon Nitride Porous Nanotubes for Enhanced Photocatalytic Hydrogen Evolution

The photocatalytic activity of g-C3N4 can be enhanced by improving photoinduced carrier separation and exposing sufficient reactive sites. In this study, we synthesized B-doped porous tubular g-C3N4 (BCNT) using a H3BO3-assisted supramolecular self-template method, wherein H3BO3 helped in B-doping, building a porous structure, and maintaining one-dimensional nanotubes. The tubular structure had an ultrathin tube wall and large aspect ratio, which are conducive to the directional transmission and separation of photogenerated carriers; moreover, the abundant pore structure of the tube wall could fully expose the reactive sites. The introduction of B and the cyano group modulated the bandgap of g-C3N4 and elevated the position of the conduction band, thus enhancing the photoreduction ability and effectively improving the hydrogen evolution performance. Consequently, the hydrogen evolution of BCNT-2 (220.8, 53.2 μmol·h-1) was 1.82 and 1.54 times that of ultrathin g-C3N4 nanosheets (CNN, 121.3, 34.6 μmol·h-1) under simulated sunlight and LED lamp irradiation, respectively. Thus, this work provides in-depth insights into the rational design of one-dimensional g-C3N4 nanotubes with high hydrogen evolution activity under visible irradiation.

Valorization of the treatment of antibiotic and organic contents generated from an in-situ-RAS-like shrimp farming pond by using graphene-quantum-dots deposited graphitic carbon nitride photocatalysts

In this study, we investigated the possibility of a photocatalytic system that uses graphene-quantum-dot (GQD)-deposited graphitic carbon nitride (g-C3N4) to treat tetracycline (TC) and other organic compounds generated from an in-situ-recirculatory-aquaculture-system (RAS)-like shrimp farming pond. GQDs were successfully deposited on the exfoliated g-C3N4 base through a hydrothermal treatment. The results showed that the incorporation of GQDs into the g-C3N4 enhanced its porosity without aggregating its mesoporous structure. The GQDs-deposited g-C3N4 photocatalysts revealed sheet-like structures with nanopores on their surface that facilitate photocatalysis. More than 90% of the TC was removed by the photocatalysts under UV-LED irradiation. Low loadings of GQDs over g-C3N4 resulted in a faster and more effective photocatalysis of TC, mainly driven by.O2- radicals. The photocatalysts were also applicable in the degradation of organic compounds with 27% of the total organic compounds (TOC) being removed from the wastewater of a RAS-like shrimp farming pond.

{Ru(C6 H6 )}-Decorating Heteropolymolybdate for Highly Activity Photocatalytic Oxidation of Benzyl Alcohol to Benzaldehyde

An unclassical structure of {Ru(C6 H6 )}-based polyoxometalate, Cs6 H4 [Te2 Mo12 O46 {Ru(C6 H6 )}] ⋅ 16.5H2 O (1), has been successfully constructed from {Te2 Mo12 O46 }-type heteropolymolybdate and {Ru(C6 H6 )} group, which structure type was discovered for the first time. Compound 1 not only possesses strong light-harvesting ability, but also exhibits high carrier separation efficiency and lower charge transfer resistance. Under visible light irradiation, compound 1 displayed excellent catalytic activity and circularity in the conversion of benzyl alcohol to benzaldehyde (yield=94 %; turnover number=500; turnover frequency=20.8 h-1 ). Finally, the electron paramagnetic resonance measurement and energy level matching analysis provide theoretical basis for the derivation of the reaction mechanism.

P-N Heterojunction Embedded CuS/TiO2 Bifunctional Photocatalyst for Synchronous Hydrogen Production and Benzylamine Conversion

The coupling of photocatalytic hydrogen production and selective oxidation of benzylamine is a topic of significant research interest. However, enhancing the bifunctional photocatalytic activity in this context is still a major challenge. The construction of Z-scheme heterojunctions is an effective strategy to enhance the activity of bifunctional photocatalysts. Herein, a p-n type direct Z-scheme heterojunction CuS/TiO2 is constructed using metal-organic framework (MOF)-derived TiO2 as a substrate. The carrier density is measured by Mott-Schottky under photoexcitation, which confirms that the Z-scheme electron transfer mode of CuS/TiO2 is driven by the diffusion effect caused by the carrier concentration difference. Benefiting from efficient charge separation and transfer, photogenerated electrons, and holes are directedly transferred to active oxidation and reduction sites. CuS/TiO2 also exhibits excellent bifunctional photocatalytic activity without noble metal cocatalysts. Among them, the H2 evolution activity of the CuS/TiO2 is found to be 17.1 and 29.5 times higher than that of TiO2 and CuS, respectively. Additionally, the yields of N-Benzylidenebenzylamine (NBB) are 14.3 and 47.4 times higher than those of TiO2 and CuS, respectively.

Rational design of bimetallic sites in covalent organic frameworks for efficient photocatalytic oxidative coupling of amines

The conversion of organic compounds by photocatalysis under mild conditions is an environment-friendly alternative for organic transformations. In this work, the bimetallic covalent organic framework coordinated by Sr2+ and Fe2+ in the porphyrin centers with molar ratio of 2:1 (COF-Sr2Fe1) was synthesized through a two-step reaction. Under the synergistic regulation of Sr2+ and Fe2+, the separation of photogenerated charges and visible light absorption for COF-Sr2Fe1 were significantly promoted, and thus COF-Sr2Fe1 exhibited efficient photocatalytic performance towards benzylamine oxidative coupling reaction with a yield of 97 %, much higher than that of the nonmetallic covalent organic framework COF-366. Moreover, it was found that the Fe site displayed higher dehydrogenation ability and the Sr site displayed higher CN coupling ability through the density functional theory (DFT) calculations, thereby making the dehydrogenation and CN coupling steps more controllable for benzylamine oxidative coupling reaction by COF-Sr2Fe1. This work provides a strategy for designing efficient covalent organic frameworks photocatalysts, and helps to understand the oxidative coupling of amines more deeply.

Enhancing photocatalytic hydrogen production of carbon nitride: Dominant advantage of crystallinity over mass transfer

Mass transfer enhancement and crystallinity engineering are two prevailing technologies for photocatalyst modification. However, their relative effectiveness in enhancing photocatalytic activity remains unclear due to the lack of rational probing catalysts. In this study, we synthesized two distinct carbon nitride (C3N4) catalysts: one with a high specific surface area (CN-HA) and the other with improved crystallinity (CN-HC). These catalysts served as probes to compare their respective impacts on photocatalytic activities. Comprehensive characterization techniques and density functional theory (DFT) calculation results unveiled that crystallinity played a dominant role in light absorption and charge dynamics, while surface area primarily influenced mass transfer in photocatalysis. Importantly, our findings revealed that crystallinity engineering of photocatalyst achieved a greater impact on photocatalytic hydrogen evolution than that from mass transfer enhancement. Consequently, CN-HC demonstrated a remarkable improvement in photocatalytic performance for hydrogen evolution (6465.4 μmol h-1 g-1), surpassing both C3N4 and CN-HA by 19.4- and 2.4-fold, respectively, accompanied by a high apparent quantum yield of 23.8 % at 420 nm. This study not only unveils the dominant factor influencing the activity of photocatalysts but also provides a modified approach for robust solar fuel production, shedding light on the path toward efficient and sustainable energy conversion.

Nanoflower-like graphitic carbon nitride aerogel: Artful cyanuric acid-controlled synthesis and enhanced photocatalytic hydrogen evolution activity

The previously reported studies on cyanuric acid-assembly strategy usually ignores the promoting function of cyanuric acid in the production of g-C3N4, limiting the development of molecular assembly strategies. In this study, a cyanuric acid-controlled synthesis strategy involving the pre-assembly of cyanuric acid with melamine and subsequent one-step calcination was developed to produce a three-dimensional (3D) nanoflower-like graphitic carbon nitride (g-C3N4) aerogel. Some cyanuric acid molecules underwent a polycondensation reaction with melamine during the pre-assembly process and finally polymerized into the g-C3N4 structure during subsequent calcination. Meanwhile, the remaining cyanuric acid molecules assembled with melamine via hydrogen-bond interactions and underwent incomplete decomposition during subsequent calcination, which not only promoted the production of 3D nanoflower-like aerogel structures, but also introduced the carbonyl (CO) and hydroxyl (-OH) groups onto the g-C3N4 surface, resulting in the successful generation of a 3D nanoflower-like oxygen-modified g-C3N4 aerogel. Moreover, the fabricated g-C3N4 aerogel exhibited a greatly enhanced H2 production rate (1573 μmol h-1 g-1), which is ∼ 6.6 times higher than that of bulk g-C3N4 (239 μmol h-1 g-1) owing to the synergistic promotion function of ultrathin nanoflower-like aerogel and oxygen modification structures. This strategy provides a theoretical basis for the development of highly efficient g-C3N4 photocatalysts via molecular assembly.

Dual Z-scheme TCN/ZnS/ ZnIn2S4 with efficient separation for photocatalytic nitrogen fixation

The development of an efficient catalyst that can use solar energy for NH3 production is of great significance in solving the environmental and energy crisis caused by the traditional ammonia synthesis process. In this work, a dual Z-scheme tubular carbon nitride/zinc sulfide/zinc indium sulfide ternary composited photocatalyst (TCN/ZnS/ZnIn2S4) with excellent nitrogen photofixation performance under visible light was prepared by self-assembly and hydrothermal methods. The crystal structure studies confirmed that tubular carbon nitride (TCN) had more active sites that could promote N2 adsorption. The photochemical studies proved that the double charge transfer channel provided by the dual Z-scheme heterojunction could improve the efficiency of electron-hole separation and achieve excellent photocatalytic nitrogen fixation. The ammonia production rate of the TCN/ZnS/ZnIn2S4 catalyst was up to 136.56 μmol/L, and it also has good stability and reusability. This work provides new insight into the development of Z-scheme heterojunction photocatalysts with green and efficient nitrogen fixation.