FeCu bimetallic metal organic frameworks photo-Fenton synergy efficiently degrades organic pollutants: Structure, properties, and mechanism insight.

The high ion leaching, low photogenerated charge separation efficiency, and slow metal valence cycling of Fe-based metal organic frameworks (MOFs) have limited their application in the deep treatment of organic pollutants. Herein, FeCu bimetallic MOFs (FeCuBDC) were synthesized using a modified solvothermal method, and a coupled photo-Fenton degradation system was successfully constructed. Degradation performance tests showed that FeCuBDC could efficiently degrade 99.3% ± 0.1% of 50 mg/L phenol within 40 min. The reaction rate constants of the photo-Fenton system were 11.0 and 64.7 times higher than those of the single Fenton reaction and photocatalysis, respectively. FeCuBDC also exhibits good cycling stability, degradation generalization, and excellent photoelectric catalytic properties. Such a considerable enhancement in the overall performance pertains to the following. First, the introduction of Cu into Fe-MOFs not only improves the crystallinity and stability, but also reduces the band gap value, increases the absorption capacity of visible light, and promotes the generation of photogenerated carriers. Second, the FeCu in MOFs are all mixed valence. Initially, the high-valence FeCu captures photogenerated electrons and promotes photogenerated charge separation and transfer. Then, the low-valence FeCu adsorbs and decomposes H2O2, accelerating the valence cycling of the bimetallic sites. The core of the reaction mechanism is that FeCuBDC effectively promotes the photo-Fenton synergy.

Core-shell structure of sulphur vacancies-CdS@CuS: Enhanced photocatalytic hydrogen generation activity based on photoinduced interfacial charge transfer.

To regulate the charge flow of the photocatalyst in photocatalytic hydrogen reactions is highly desirable. In this study, a highly efficient sulphur vacancies-CdS@CuS core-shell heterostructure photocatalyst (denoted CdS-SV@CuS) was developed through the surface modification of CdS-sulphur vacancies (SV) nanoparticles by CuS based on photoinduced interfacial charge transfer (IFCT). This novel photocatalyst with modulated charge transfer was prepared by hydrothermal treatment and subsequent cation-exchange reactions. The SV confined in CdS and the IFCT facilitate the charge carrier's efficient spatial separation. The optimized CdS-SV@CuS(5%) catalyst exhibited a remarkably higher H2 production rate of 1654.53 µmol/g/h, approximately 6.7 and 4.0 times higher than those of pure CdS and CdS-SV, respectively. The high photocatalytic performance is attributed to the rapid charge separation, caused by the intimate interactions between CdS-SV and CuS in the core-shell heterostructure. This is the first time that a straightforward method is adopted to construct a metal sulphide core-shell structure for superior H2-production activity by IFCT.

Surface oxygen vacancies enriched FeOOH/Bi2MoO6 photocatalysis- fenton synergy degradation of organic pollutants.

To achieve rapid separation of photogenerated charges, increase photocatalytic degradation activity, a visible light-driven FeOOH/Bi2MoO6-OVs photocatalyst was designed and successfully fabricated via solvothermal synthesis and calcination. H2O2 was added under visible light irradiation to form a heterogeneous photocatalysis-Fenton synergy system. Using visible light irradiation, 10% FeOOH/Bi2MoO6-OVs had the best degradation activity. The removal efficiency of phenol was 100% within 3 h, which was 1.54 times and 1.33 times of the degradation efficiency of photocatalysis and Fenton alone, respectively. The catalyst has high removal activity for various pollutants and good cycle stability. Hydroxyl radicals and superoxide radicals have proven to be the main active substances and a reasonable catalytic mechanism was proposed. Surface oxygen vacancy can not only reduce the width of band gap, promote the separation and migration of photogenerated electron-hole pairs, but also make the OO bond of H2O2 elongate and weaken, making it easier to react with FeOOH and realize the synergistic effect of photocatalysis-Fenton. Simultaneously, the oxygen vacancies located near the valence band can capture holes, and the holes are rapidly transferred to the surface of the catalyst and participated in the degradation of pollutants.

Tuning the Supramolecular Structures of Metal-Free Porphyrin via Surfactant Assisted Self-Assembly to Enhance Photocatalytic Performance.

Metal-free porphyrin with good planarity is beneficial to π-π stack interactions, which promotes electron coupling and the separation and transfer of photogenerated carriers. It is necessary to develop metal-free porphyrin-based photocatalysts and exploit the photocatalytic mechanism. Herein, metal-free porphyrin (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, TCPP) was self-assembled through an acid-based neutralization reaction and mixing dual-solvents under surfactants to form different aggregates. Morphology structures, optical and optoelectronic properties of the TCPP aggregates were characterized in detail. TCPP self-assemblies showed higher photocatalytic activities for the degradation of phenol under visible light than untreated TCPP powders, and the aggregates of nanorods formed through the acid-based neutralization reaction in the presence of hexadecyl trimethyl ammonium bromide (CTAB) possessed 2.6 times more activity than the nanofiber aggregates formed through mixing dual-solvents. It was proved that self-assembly methods are crucial for controlling the aggregation of porphyrins to form different aggregations, which have a profound impact on the photocatalytic activity.

Enhancement of Photocatalytic Activity under Visible Light Irradiation via the AgI@TCNQ Core-Shell Structure.

In this paper, a AgI@TCNQ photocatalyst with a core-shell structure was reported. A two-dimensional TCNQ (7,7,8,8-Tetracyanoquinodimethane) nanosheet, with a π-π conjugate structure, was used as a shell layer to realize the flexible coating on the surface of AgI nanoparticles. These special core-shell structure composites solve the key problems of the small interface of the bulk composites and the lesser charge transfer paths, which could accelerate the migration of photogenerated carriers. Thus, the AgI@TCNQ photocatalysts showed the better photodegradation performance for the methylene blue (MB) solution, and the degradation rate of AgI@TCNQ (1 wt.%) composite was 1.8 times than AgI under irradiation. The reactive species trapping experiments demonstrated that ·O2-, h+, and ·OH all participated in the MB degradation process. The photocatalytic mechanism of AgI@TCNQ composites could be rationally explained by considering the Z-scheme structure, resulting in a higher redox potential and more efficient separation of charge carriers. At the same time, the unique core-shell structure provides a larger contact area, expands the charge transport channel, and increases the surface active sites, which are beneficial for improving photocatalytic performance.

Surface Decoration of ZnWO4 Nanorods with Cu2O Nanoparticles to Build Heterostructure with Enhanced Photocatalysis.

The surface of ZnWO4 nanorods was decorated with Cu2O nanoparticles (Cu2O/ZnWO4) prepared through a precipitation method. The Cu2O nanoparticles were tightly deposited on the ZnWO4 surface and had average diameters of 20 nm. The nanoparticles not only promoted the absorption and utilization of visible light but also facilitated the separation of photogenerated charge carriers. This brought an improvement of the photocatalytic activity. The 5 wt % Cu2O/ZnWO4 photocatalyst displayed the highest degrade efficiency for methylene blue (MB) degradation under visible light, which was 7.8 and 2 times higher than pure ZnWO4 and Cu2O, respectively. Meanwhile, the Cu2O/ZnWO4 composite photocatalyst was able to go through phenol degradation under visible light. The results of photoluminescence (PL), photocurrent, and electrochemical impedance spectra (EIS) measurements were consistent and prove the rapid separation of charge, which originated from the match level structure and the close contact with the interface. The radical and hole trapping experiments were carried out to detect the main active substances in the photodegradation process. The holes and ·O2- radicals were predicted to dominate the photocatalytic process. Based on the characterization analysis and experiment results, a possible photocatalytic mechanism for enhancing photocatalytic activity was proposed.

Facile synthesis of an Ag@AgBr nanoparticle-decorated K4Nb6O17 photocatalyst with improved photocatalytic properties.

An Ag@AgBr nanoparticle-decorated K4Nb6O17 (Ag@AgBr/K4Nb6O17) photocatalyst was prepared via the oil-in-water self-assembly method. The Ag@AgBr nanoparticles, with average diameters of 20 nm, were uniformly deposited on the K4Nb6O17 surface. The as-prepared Ag@AgBr/K4Nb6O17 composites exhibited high visible light absorption, high photocurrent intensity, and high charge transfer efficiency, thus enhancing the photocatalytic performance for methyl-blue (MB) dye degradation. The Ag@AgBr (20 wt%)/K4Nb6O17 composite displayed the highest photocatalytic activity, degrading 96% of the MB solution under visible light irradiation for 60 min, which was 2.3-times and 8.5-times that of the bulk Ag@AgBr and K4Nb6O17, respectively. The excellent photocatalytic activity of the Ag@AgBr/K4Nb6O17 composites is due to the synergistic effect between Ag@AgBr and K4Nb6O17, where the Ag@AgBr nanoparticles not only enhanced visible light absorption efficiency due to the Ag nanoparticles' SPR, but also greatly accelerated the separation of the photogenerated electron-hole pairs. From the UV-vis spectra, the Ag@AgBr nanoparticles greatly extend the composites' visible light absorption. The data collected from photoluminescence (PL), photocurrent and electrochemical impedance spectra (EIS) were consistent and confirmed the rapid separation of charge carriers. Moreover, the composite exhibited a larger specific surface area, which was also beneficial for the photocatalytic activity. In addition, the roles of the radical species were investigated, and the holes and ·O2 - radicals were hypothesized to dominate the photocatalytic process. Based on the characterization analysis and experimental results, a possible photocatalytic mechanism for the enhancement of photocatalytic activity is proposed.

Two copper(i) cyanide coordination polymers modified by semi-rigid bis(benzimidazole) ligands: syntheses, crystal structures, and electrochemical and photocatalytic properties.

Two Cu(i) cyanide coordination polymers (CPs), namely, [Cu2(L1)(CN)2]n (1) and [Cu2(L2)(CN)2]n (2) (L1 = 4,4'-bis(2-methylbenzimidazol-1-ylmethyl)biphenyl, L2 = 4,4'-bis(5,6-dimethylbenzimidazol-1-ylmethyl)biphenyl) were synthesized and structurally characterized by single crystal X-ray diffraction, IR spectroscopy, X-ray powder diffraction and elemental analysis. The cyanide ligands in these CPs are generated in situ from the C-C bond cleavage of acetonitrile under solvothermal conditions, which is environmentally friendly and used conveniently. CP 1 features a three-fold interpenetration 3D framework consisting of Cu10(CN)6(L1)4 rings, which represents the first investigation on introducing bis(benzimidazole) ligands into copper(i) cyanide CPs with ThSi2 topology, while CP 2 exhibits a two-dimensional (6,3) layered structure containing Cu6(CN)4(L2)2 rings. The thermal stabilities, and photoluminescence and electrochemical behavior in the solid state of CPs 1 and 2 have been investigated in detail. Moreover, both CP 1 and CP 2 manifest promising photocatalytic activities (photodegradation efficiency using CP 1 is 90.8% and using CP 2 is 87.2%) for the degradation of methylene blue (MB) under UV light irradiation. A possible photocatalytic mechanism is suggested by introducing t-butyl alcohol (TBA) as a widely used ˙OH scavenger.

Novel Cu2O quantum dots coupled flower-like BiOBr for enhanced photocatalytic degradation of organic contaminant.

Here we report a highly efficient novel photocatalyst consisting of Cu2O quantum dots (QDs) incorporated into three-dimensional (3D) flower-like hierarchical BiOBr (hereafter designated QDs-Cu2O/BiOBr), which were synthesized via a simple reductive solution chemistry route and applied to decontaminate the hazardous wastewater containing phenol and organic dyes. The deposition of Cu2O QDs onto the surface of the BiOBr was confirmed by structure and composition characterizations. The QDs-Cu2O/BiOBr composites exhibited superior activity for organic contaminant degradation under visible light and 3 wt% QDs-Cu2O/BiOBr composite showed the highest degrade rate for phenol and methylene blue (MB), which was 11.8 times and 1.4 times than that of pure BiOBr, indicated the QDs-Cu2O/BiOBr composite has the great potential application in purifying hazardous organic contaminant. The incorporated Cu2O QDs played an important role in improving the photocatalytic performance, due to the enhancement of visible light absorption efficiency as well as the efficient separation of the photogenerated charge carriers originating from the intimately contacted interface and the well-aligned band-structures, which was confirmed by the results of PL, photocurrent and EIS measurements. The possible photocatalytic mechanism was proposed based on the experiments and theoretical results.