Migration Of Photoinduced Charge Carriers Research Articles

Visible-light induced ofloxacin photodegradation catalyzed by the S-scheme Bi2MoO6/NH2-MIL-68(In) heterojunction: Interfacial engineering, DFT calculations, and toxicity assessment

The construction of photocatalysts with high efficiencies for visible light utilization and rapid migration of photoinduced charge carriers is essential for efficient photodegradation of contaminants in water. Thus, a novel Bi2MoO6/NH2-MIL-68(In) S-scheme heterostructure photocatalyst was synthesized via a hydrothermal method. The ofloxacin photodegradation efficiency of optimized BMN-2 reached 100 % within 90 min of visible-light illumination. In addition, an S-scheme charge migration pathway was confirmed within BMN-2 based on work function calculations, in situ XPS, and ESR studies. The photocatalytic mechanism, potential intermediates, and four photodegradation pathways were proposed from theoretical calculations and experimental studies. In addition, h+, •O2–, and •OH were the predominant active species identified via scavenger experiments and ESR spectroscopy. Moreover, the comprehensive toxicity of the degraded OFL solution was lower than that of the initial solution, as indicated by QSAR predictions and E. colicultivation.

Augmented photocatalysis induced by 1T-MoS2 bridged 2D/2D MgIn2S4@1T/2H-MoS2 Z-scheme heterojunction: mechanistic insights into H2O2 and H2 evolution.

In the realm of composite photocatalysts, the fusion of the co-catalyst effect with interfacial engineering is recognized as a potent strategy for facilitating the segregation and migration of photo-induced charge carriers. Herein, an innovative mediator-based Z-scheme hybrid, i.e. MIS@1T/2H-MoS2, has been well designed by pairing MIS with 1T/2H-MoS2via a facile hydrothermal strategy as a competent photocatalyst for H2O2 and H2 generation. The co-catalyst, i.e. metallic 1T-phase bridging between semiconducting 2H-MoS2 and MIS, serves as a solid state electron mediator in the heterostructure. Morphological findings revealed the growth of 1T/2H-MoS2 nanoflowers over MIS microflowers, verifying the close interaction between MIS and 1T/2H-MoS2. By virtue of accelerated e-/h+ pair separation and migration efficiency along with a proliferated density of active sites, the MMoS2-30 photocatalyst yields an optimum H2O2 of 35 μmol h-1 and H2 of 370 μmol h-1 (ACE of 5.9%), which is 3 and 2.7 fold higher than pristine MIS. This obvious enhancement can be attributed to photoluminescence and electrochemical aspects that substantiate the diminished charge transfer resistance along with improved charge carrier separation, representing a good example of a noble metal-free photocatalyst. The proposed Z-scheme charge transfer mechanism is aided by time-resolved photoluminescence (TRPL), XPS, radical trapping experiments, and EPR analysis. Overall, this endeavour provides advanced insights into the architecture of noble metal-free Z-scheme heterostructures, offering promising prospects in photocatalytic applications.

Interfacial Mo-S bond-reinforced hierarchical S-scheme heterostructure of Bi2MoO6@ZnIn2S4 for highly-selective and efficient CO2 photoreduction into CO

Developing highly-selective and efficient photocatalysts for converting CO2 into carbon-based fuels by solar energy is desirable, whereas it is still a severe challenge. Herein, we present a unique interfacial Mo-S bond-bridged hierarchical S-scheme heterostructured photocatalysts, prepared by in-situ loading ZnIn2S4 nanoflakes (ZIS-NFs) on the Bi2MoO6 porous micro-spheres (BMO-PMs) assembled from numerous nanosheets. The interfacial Mo-S bonds can reinforce the separation and migration of photoinduced charge carriers via the S-scheme mechanism in the BMO@ZIS heterostructure. Besides, its hierarchical heterostructure can improve the visible-light response ability, and afford plenty of active sites so as to benefit the CO2 adsorption and activation. Specifically, the combined results of experiment and density functional theory (DFT) calculations indicate that the fine heterostructure can not only convert the endoergic rate-determining step of bare ZIS (namely, CO2* hydrogenation to form COOH*) to an exoergic reaction process and lower the overall activation energy barrier, but also boost the desorption of CO* from the ZIS surface. As a result, in existence of H2O vapor without any sacrificial agents, the optimum photocatalyst (BMO@ZIS-0.4) manifests the outstanding CO2 photoreduction activity, with a CO yield and selectivity of 23.11 μmol g−1h−1 and 93.1 %, respectively, higher than those of the most reported photocatalysts. This work offers an in-depth insight for fabricating the interfacial chemical bond-modulated hierarchical S-scheme heterostructure with a remarkable performance of CO2 conversion.

Decorating CdS with cobaltous hydroxide and graphene dual cocatalyst for photocatalytic hydrogen production coupled selective benzyl alcohol oxidation

Coupling photocatalytic H2 evolution with benzyl alcohol (BA) oxidation to benzaldehyde (BAD) reaction allows the full utilization of the energy of light-induced electron and hole to produce fuel and valuable chemicals, which has received widespread attention recently. Herein, Co(OH)2 nanosheet array-graphene(GR) composites cocatalyst can be successfully synthesized by simple precipitation method, and then CdS nanoparticles are in situ grown in hybrid cocatalyst to finally obtain CdS-Co(OH)2-GR ternary photocatalysts. Composting of dual-cocatalyst with CdS facilitates the migration of photoinduced charge carriers of CdS, affords abundant active sites and makes the growth of CdS nanoparticles more uniform and dispersed. As a result, the CdS-Co(OH)2-GR ternary composites have shown a glorious performance, showing the H2 generation velocity of 1173.53 µmol h−1 g−1, and the conversion rate of benzyl alcohol has reached 100 % within 2 h, which has surpassed other prepared samples and most of analogous photocatalyst systems. We are confident that this study can supply a useful reference for the synthesis of dual-cocatalyst-modified semiconductor composites, and promote the development of photocatalytic coupling reaction system, in which sacrifice agents are free and energies of light-induced electron and holes can be fully utilized.

Interface engineering of 0D/2D Cu2O/BiOBr Z-scheme heterojunction for efficient degradation of sulfamethoxazole: Mechanism, degradation pathway, and DFT calculation

Constructed heterojunction has been considered an efficient strategy to enhance the migration and transfer of photoinduced charge carriers. Herein, a Z-scheme Cu2O/BiOBr heterojunction with 0D/2D structure was fabricated by microwave hydrothermal method. It was found that the optimal composites photocatalyst showed excellent activity for sulfamethoxazole (SMZ) illumination, and the removal rate reached 90.7%, which was higher than pristine Cu2O (53.0%) and BiOBr (60.0%). Subsequently, the operational parameters such as catalyst dosage, concentrations of pollutants, and pH of solution were investigated. According to the ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRs), Mott-Schottky curve, and density functional theory (DFT) analysis, the Z-scheme degradation mechanism of Cu2O/BiOBr heterostructure was proposed. Among them, the interface structure of 0-dimensions/2-dimensions (0D/2D) can significantly increase the number of heterojunctions in the composite catalyst, and Z-scheme heterostructures can accelerate the generation and migration of photoinduced charge carriers, which has a facilitation effect on improving the decomposition activity of the photocatalyst. Moreover, three possible pathways for SMZ degradation were inferred. This study provides a promising strategy for constructing novel heterojunctions with high photocatalytic performance.

In situ low-temperature pyrolysis fabrication type II BiOIO3/Bi4O5I2 heterostructures with enhanced visible-light-driven photooxidation activity.

Novel visible-light-driven heterostructure semiconductors are considered as promising photocatalysts for the elimination of environmental organic pollutants. Herein, a solvent-assisted low-temperature in situ calcination strategy was developed to fabricate type II BiOIO3/Bi4O5I2 heterojunction by using BiOIO3 as self-sacrificed template. The phase transition temperature of BiOIO3 was reduced under solvent-assisted operating conditions. By controlling the elevated temperature from 200 to 300 °C, an in situ stepwise pyrolysis reaction occurred during the calcination process, which was described as BiOIO3 → BiOIO3/Bi4O5I2 → Bi4O5I2. The light absorption edge of different samples significantly red shifted from 385 to 632 nm with the increase of calcination temperature. Meanwhile, two interlocked interface lattice fringes were identified in high resolution transmission electron microscope (HRTEM) of BiOIO3/Bi4O5I2-250 composites, confirming the formation of BiOIO3/Bi4O5I2 heterojunction. The as-obtained BiOIO3/Bi4O5I2 heterojunction demonstrated the optimal photodegradation performance, which brought about 99.4% of bisphenol A (BPA) degraded within 30 min visible light (λ > 420 nm) illumination. Besides, after 5 repeated cycles, the photoactivity of BiOIO3/Bi4O5I2 heterojunction still maintained 91.5%, unfolding its high photostability. The superior photoreactivity of BiOIO3/Bi4O5I2 nanosheets was assigned to the formation of well-matched type II heterojunction, which significantly enhanced the separation and migration of photoinduced charge carriers. Superoxide radical (O2-) and hole (h+) are dominant reactive species in this photodegradation system. Based on active species quenching experiments and electron paramagnetic resonance (ESR) measurements, a possible type II heterojunction mechanism for enhanced photodegradation performance of BiOIO3/Bi4O5I2 heterostructure was proposed. This work affords an innovative method for design and construction of type II composites toward sustainable water purification.

Graphitic carbon nitride engineered α-Fe2O3/rGO heterostructure for visible-light-driven photochemical oxidation of sulfamethoxazole

Rational design of semiconductor photocatalysts is an effective way to achieve efficient visible-light-driven environmental remediation. Herein, a series of graphitic carbon nitride (g-C3N4) engineered hematite (Fe2O3)/reduced graphene oxide (rGO) photocatalysts were synthesised and employed in visible-light-driven photo-Fenton-like degradation of sulfamethoxazole (SMX). The exceptional performance of the optimal photocatalyst (0.4-FerGCN-3) was achieved because of the successful structural integration of g-C3N4/Fe2O3/rGO for efficient separation and migration of photoinduced charge carriers (e−/h+). Photochemical decomposition efficiency was also optimised by analysing the important reaction parameters such as initial catalyst loading, initial H2O2 dosage, pH, and reaction temperature. Detailed studies on the generation of reactive species and degradation intermediates were performed to propose a possible mechanism for SMX degradation. The findings may provide not only a strategy for nanostructure engineering of semiconductor photocatalysts but also insights into the effective remediation of emerging contaminants such as SMX.

Facile layer-by-layer self-assembly of 2D perovskite niobate and layered double hydroxide nanosheets for enhanced photocatalytic oxygen generation

Photocatalytic O2-generation reaction is recognized as a crucial step in water splitting and has drawn great attention of researchers. In this work, a hetero-layered composite photocatalyst was successfully prepared by a facile self-assembly method based on electrostatic interaction between oppositely charged Zn/Cr-layered double hydroxide (Zn/Cr-LDH) and lead niobate nanosheets. The layer-by-layer stacking of Zn/Cr-LDH and HPb2Nb3O10 nanosheets was beneficial for rapid migration of photo-induced charge carriers inside the photocatalyst because of large contact area. In the meantime, Zn/Cr-LDH and HPb2Nb3O10 components exhibited suitable energy-band alignment, which led to efficient separation of photo-induced charge carriers. The composite photocatalyst showed enhanced photocatalytic O2-generation activity under visible-light irradiation without loading cocatalyst. Briefly, this work expanded the applications of AB2Nb3O10-based materials in photocatalytic energy conversion and proved that constructing composites based on electrostatic self-assembly of complementary 2D materials is a promising strategy for development of more efficient photocatalysts.

High efficiency photocatalytic CO2 reduction realized by Ca2+ and HDMP group Co-modified graphitic carbon nitride

The development of highly efficient and visible-light responsive carbon nitride (CN) photocatalysts is desirable to address energy shortages and environmental pollution challenges. Herein, we synthesized novel 2-hydroxy-4,6-dimethylpyrimidine (HDMP) group and Ca2+ co-modified carbon nitride (CN) photocatalyst (CN-CAA) using a facile in situ copolymerization procedure employing urea and calcium acetylacetonate (CAA) as precursors. The HDMP group and Ca2+ co-modification contributed to increased electron density and modulated electronic structure, resulting in extended visible light harvesting and accelerated separation and migration of photoinduced charge carriers. Benefiting from the enhanced visible light utilization and improved photoexcited carriers separation and transportation, the CN-CAA exhibited significantly elevated visible-light-driven photocatalytic activity for CO2 reduction. This work provided a new insight into the photocatalytic performance promotion of CN through molecular engineering and metal ions incorporation co-modification.

Photocatalytic overall water splitting without noble-metal: Decorating CoP on Al-doped SrTiO3

CoP, a noble-metal-free cocatalyst, was first introduced onto the surface of Al-doped SrTiO3 (Al:STO) via an in situ photodeposition-phosphorization method for photocatalytic overall water splitting (POWS) into stoichiometric H2 and O2. Compared with pure Al:STO, the POWS activity was enhanced by a factor of ~ 421 over 1.0%CoP/Al:STO, with the highest evolution rates of 2106 and 1002 μmol h−1 g−1 for H2 and O2, respectively. The mechanism for the remarkably boosted POWS activity was systematically analyzed based on the comprehensive characterization. On the one hand, benefiting from the in situ photodeposition process, CoP with metallic character were intimately decorated onto the surface of Al:STO and accelerated the separation and migration of photoinduced charge carriers. On the other hand, CoP, serving as reactive sites for H2 evolution reaction, lowered the overpotential and facilitated the surface reduction reaction, thereby enhancing the POWS activity. Furthermore, Cr2O3 was photodeposited on the surface of 1.0%CoP/Al:STO composite to suppress the undesired reverse reaction and the POWS activity was further enhanced up to 3558 and 1722 μmol h−1 g−1 for H2 and O2, respectively, with apparent quantum yield of 7.1% at 350 ± 10 nm. This work presents a new avenue for designing POWS system without noble-metal cocatalyst.

Hydrothermally synthesized mesoporous CS-g-PA@TSM functional nanocomposite for efficient photocatalytic degradation of Ciprofloxacin and treatment of metal ions

Tin-based ternary inorganic semiconductors enable new opportunities for the development of functional hydrogel nanocomposites to cope with environmental pollution. In this regard, we have synthesized highly functionalize CS-g-PA@TSM nanocomposites by the impregnation of Tin- Si/Mo (TSM) semiconductor in the matrix of chitosan/polyacrylamide (CS-g-PA) using the hydrothermal route. Multifunction platform showed ammonia vapor sensing, fluorescent detection as well as removal and exchange recovery of lead ions from wastewater and its photocatalytic behavior towards antibiotic degradation. The CS-g-PA@TSM nanocomposite achieved almost 96% photodegradation towards Ciprofloxacin (CIP) after 130 min of irradiation which was further monitored and confirmed by 3-D excitation-emission matrix fluorescence and GC–MS techniques, respectively. The photocatalytic mechanism of the CS-g-PA@TSM under visible light irradiation was clarified, which established the generation of O2− / OH species in the form of dominant radicals. The experimental results indicated that the improved photocatalytic performance of CS-g-PA@TSM could be attributed to enhance the optical absorption and efficient separation along with the migration of photoinduced charge carriers. The nanomaterial also exhibits significant Pb2+ recovery (95.6%) from wastewater with a limit of detection (LOD) and limit of quantification (LOQ) as 3.38 μg L−1 and 9.34 μg L−1, respectively. The CS-g-PA@TSM nanocomposite was successfully employed up to five regeneration cycles with 98% regeneration capacity. Thus, the finding of the present study establishes that the multifunctional CS-g-PA@TSM nanocomposite platform could be used for the treatment of antibiotics (CIP), ammonia, and Pb2+ from wastewater.

In situ plasmonic Bi grown on I− doped Bi2WO6 for enhanced visible-light-driven photocatalysis to mineralize diverse refractory organic pollutants

Plasmonic Bi metal and I− dopant co-modified Bi2WO6 photocatalysts were successfully fabricated through a one-pot solvothermal method. The samples were characterized by multiple techniques to explore their crystalline structures, surface morphologies, photoelectric properties and photocatalytic performance. The photocatalytic activity of I-Bi/Bi2WO6 samples was evaluated by degrading diverse organic pollutants, including colorless Bisphenol A (BPA), cationic dye Rhodamine B (RhB), anionic dye Congo red (CoR), antibiotic Sulfamethoxazole (SX) and pesticide Atrazine (AZ). The results revealed that 1/5 I-Bi/Bi2WO6 (I:W = 1:5) possessed the best photocatalytic performance for degrading BPA, RhB, CoR, SX and AZ. The improved photocatalytic performance was mainly attributed to the enhanced the visible light harvesting caused by the impurity level generated via the I− dopant and effective separation and migration of photoinduced charge carriers. Moreover, the SPR effect of metallic Bi is also a key factor for the enhancement of photocatalytic performance. Additionally, the 1/5 I-Bi/Bi2WO6 sample also showed excellent photochemical stability after five cyclic tests. This work could be a basic platform for investigating impurity doping and surface metallization co-modified photocalysts with remarkable photocatalytic performance for the environmental pollution degradation.

Efficient day-night photocatalysis performance of 2D/2D Ti3C2/Porous g-C3N4 nanolayers composite and its application in the degradation of organic pollutants

It is hindered by the limited light time that the development of photocatalysis technology, which is a clean and energy-saving advanced oxidation process. In this work, a 2D/2D Ti3C2/porous g-C3N4 nanolayers composited van der Waals (VDW) heterostructure photocatalyst (Ti3C2/PCN) was prepared by a straightforward vacuum filtration method after an ultrasonic stripping process. In this Ti3C2/PCN composite photocatalyst, PCN nanolayers play the role of absorbing visible light, while Ti3C2 nanolayers form VDW heterojunction with PCN nanolayers, which is beneficial to migration of photo-generated electrons from PCN to Ti3C2. The band structure match of Ti3C2/PCN and the build-in electric field from the VDW heterojunction both favor the effective separation and migration of photo-induced charge carriers that is why the Ti3C2/PCN composite shows good day-photocatalytic capability with 98% phenol removal efficiency. Besides, as a good electronic storage material, the Ti3C2 can store excess photo-generated electrons under light irradiation and release them when exposed to electron acceptors in the dark condition. Therefore, the night-photocatalysis can work out even without sunlight, in which 32% phenol was decomposed. In addition, the universality of Ti3C2/PCN day-night photocatalytic system is proved by the degradation of various organic pollutants. The design of this day-night photocatalyst can facilitate the application of photocatalytic reaction to actual environmental scenes, since it reduces the limitation imposed by the presence or absence of sunlight.

Fabrication of Ag quantum dot/SnIn4S8 Schottky junction with enhanced photocatalytic inactivation of E. coli under visible light excitation

A highly efficient visible light driven Ag quantum dots (QDs)/SnIn4S8 Schottky junction photocatalyst was fabricated and applied for the inactivation of E. coli cells under visible light irradiation (λ > 420 nm). The 100 Ag QDs/SnIn4S8 composite displayed the highest inactivation ability with about 7.4 log cfu ml−1 of E. coli cells completely deactivated within 5 h visible light irradiation. The photocatalytic inactivation mechanism could be explained by the broken cell membrane, leakage and damage of biomolecules (proteins and DNA) as proved by scanning electron microscopy, electrophoresis, fluorescence-based stain and reactive species trapping experiments. The reactive species h+, and e− were involved in the bactericidal process over the Ag QDs/SnIn4S8 system. Moreover, the enhanced photoinactivation activity of Ag QDs/SnIn4S8 composites could be ascribed to the enhancement of light absorption by the surface plasmon resonance effect, the formation of the Schottky junction to facilitate the separation and migration of photoinduced charge carriers and the higher number of active sites provided by the enlarged specific surface area.

Interfacial charge-transfer transitions enhanced photocatalytic activity of TCNAQ/g-C3N4 organic hybrid material

Abstract Graphitic carbon nitride (g-C3N4) photocatalyst has a promising application prospect in solving environment problems and energy crisis. In order to improve the photocatalytic activity of g-C3N4, a novel TCNAQ/g-C3N4 organic hybrid photocatalyst was designed by introducing 11,11,12,12-tetracyanonaphtho-1,4-quinodimethane (TCNAQ) as an electron acceptor. Due to the interfacial charge-transfer transitions between g-C3N4 donor and TCNAQ acceptor, separation and migration of photo-induced charge carriers were promoted, while their recombination was prohibited, which led to enhanced photocatalytic performance in pollutant degradation. This work provides a strategy to produce efficient hybrid photocatalysts with high light-to-current conversions due to the interfacial charge-transfer transitions, which have potential applications in light-to-energy conversions.

Ultrathin 2D/2D ZnIn2S4/MoS2 hybrids for boosted photocatalytic hydrogen evolution under visible light

A well-connected hetero-layered ZnIn2S4/MoS2 composite was fabricated via an electrostatic self-assembly process to boost photocatalytic hydrogen evolution under visible-light irradiation. Ultrathin nanosheets contribute to efficient charge transfer by reducing electron diffusion length. In the sheet-on-sheet heterostructure, ultrathin ZnIn2S4 nanosheets (NSs) and MoS2 NSs were well connected with each other to form a large and intimate contact interface, which features an efficient separation and migration of photoinduced charge carriers. Moreover, MoS2 NSs endow the composite with abundant active sites and lowers its overpotential for water reduction. Consequently, the ultrathin hetero-layered ZnIn2S4/MoS2 composite with optimized loading of MoS2 achieves a hydrogen production rate of 4.974 mmol g−1 h−1, which is ca. 50 times as much as that of pure ZnIn2S4, and 2.2 times as much as that of its ZnIn2S4/Pt counterpart. This work provides inspiration for the fabrication of well-contacted hetero-layered structure for photocatalytic hydrogen evolution.

Rational Fabrication of Hierarchical Z‐Scheme WO3/Bi2WO6 Nanotubes for Superior Photoelectrocatalytic Reaction

AbstractTo develop efficient and stable photocatalysts for visible light pollutant degradation, hierarchical Z‐Scheme WO3/Bi2WO6 nanotubes have been rationally designed and fabricated via a combined electrospinning‐calcination process. Moreover, the morphology of as‐fabricated nanotubes could be tuned by the annealing temperature. Accordingly, the newly‐designed hierarchical Z‐Scheme system highly facilitates the separation and migration of photoinduced charge carriers, and enhances the broadened photoabsorption range and high redox capacity owning to the synergistic effects of WO3 and Bi2WO6. Meanwhile, the corresponding possible formation mechanism is proposed as well. Benefiting from the unique structural features, the optimized 550 °C‐WO3/Bi2WO6 nanotubes exhibit the remarkable photoelectrochemical activity and photocatalytic performance for degrading pollutant models (4‐NP and RhB), among which reaction rate is superior to 500 °C and 600 °C‐WO3/Bi2WO6 counterparts. This work may shed light on rational design and construction of hierarchical Z‐Scheme WO3/Bi2WO6 nanotubes for energy and environment‐related applications.

Enhanced photocatalytic degradation of methylene blue dye using CuS[sbnd]CdS nanocomposite under visible light irradiation

The inorganic nanoparticles based semiconductor photocatalyst has attracted widespread attention for the practical applications in sustainable energy and environmental remediation due to its low cost, eco-friendly, high efficiency and ease of process. CuS, CdS and CuSCdS nanocomposite photocatalysts have been successfully synthesized by a simple hydrothermal approach. The phase purity, composition and surface morphology of as synthesized nanomaterials were characterized using various analytical techniques. The photocatalytic activities of the as-prepared materials have been evaluated by the degradation of methylene blue (MB) dye in the presence of hydrogen peroxide (H2O2) which served as an oxidant under visible light irradiation. MB dye (10 ppm) was degraded by about 80%, 59% and 99.97% for CuS, CdS and CuSCdS nanocomposite respectively at 10 min. The results demonstrate that CuSCdS nanocomposite exhibited excellent photocatalytic activity as compared to the CuS and CdS is which mainly attributed to large surface area, narrow band gap, high adsorbing capacity of the dye and also low recombination of the photo-generated electrons and holes. Further, electrochemical impedance (EI) measurement revealed that as prepared CuSCdS nanocomposite suggested that as compared to CuS and CdS, the CuSCdS nanocomposite exhibits rapid migration of photo-induced charge carriers. In addition, the CuSCdS nanocomposite demonstrated that good stability towards photocatalytic degradation even after repeated usage. Finally, a suitable photocatalytic reaction mechanism has been proposed to indicate the photocatalytic performance of the nanocomposite.

Triamterene-Grafted Graphitic Carbon Nitride with Electronic Potential Redistribution for Efficient Photocatalytic Hydrogen Evolution.

In this study, a photocatalyst with a distorted skeleton and synthesized by grafting triamterene onto graphitic carbon nitride (g-C3 N4 ) frameworks was prepared. The pteridine ring of the triamterene-based nitrogen-enriched organic structure functions as a trapped electron site owing to its inductive effect. The benzene ring in triamterene plays an important role in the even dispersion of electrons by a conjugative effect. Redistribution of the intramolecular electronic potential is caused by a synergistic effect between the pteridine and benzene rings of triamterene and promotes separation and migration of the photoinduced charge carriers. After coupling with triamterene, the π electrons of g-C3 N4 are relocated; that is, the intrinsic electronic and band structures of g-C3 N4 are effectively modulated. The modified polymeric photocatalyst shows a high photocatalytic H2 evolution rate of 157.5 μmol h-1 , a value that is 4.3 times higher than the H2 evolution rate of pristine g-C3 N4 (36.8 μmol h-1 ), with an apparent quantum efficiency of 9.7 % at λ=450 nm. The incorporation of triamterene into the g-C3 N4 frameworks significantly expands its π-delocalized system by redistribution of the electronic potential, expands the visible-light absorption range, and effectively promotes the separation and migration of photoinduced charge carriers. This strategy may provide a reference for promoting charge separation of g-C3 N4 through redistribution of the electronic potential and for synthesizing novel carbon nitride based semiconductors for efficient solar energy conversion into hydrogen.

Highly effective photoreduction of CO2 to CO promoted by integration of CdS with molecular redox catalysts through metal-organic frameworks.

We propose a strategy to synthesize ternary CdS/UiO-bpy/Co composites by integration of CdS and molecular redox catalysts through metal-organic framework (MOF) UiO-bpy. The CdS/UiO-bpy/Co composites were very effective for photocatalytic conversion of CO2 to CO under visible light irradiation. The evolution rate of CO could reach 235 μmol g-1 h-1, which was a 10.2-fold improvement compared to that for the parent CdS, and selectivity for CO was 85%. The outstanding performance of the CdS/UiO-bpy/Co composites resulted from promoting the separation and migration of photo-induced charge carriers, enhancing the adsorption of CO2 molecules, and offering abundant active sites for CO2 reduction. As far as we know, this is the first study to integrate inorganic semiconductors and molecular redox catalysts through MOFs.