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The fabrication of photocatalysts with preferable degradation ability is critical to purify wastewater. MIL-53-(Fe), as a representative Fe-based metal–organic framework (Fe-MOF), has been widely used in photocatalysis due to its excellent intrinsic characteristics. However, the inadequate electron number in MIL-53-(Fe) has restricted the ability of photodegradation of organic pollutants. Herein, desirable, energy-efficient, and environmentally friendly MIL-53-(Fe)/Sn3O4 nanosheet photocatalysts were first constructed by the solvothermal method. The characterization results indicated that the MIL-53-(Fe)/Sn3O4-5 (5 wt % Sn3O4) catalyst exhibited optimal photoelectric properties and maintained a relatively regular morphology. Moreover, the prepared MIL-53-(Fe)/Sn3O4-5 exhibited preferable photodegradation ability for dyes and antibiotics under visible light, and the maximum photodegradation capacity for malachite green, methylene blue, tetracycline, ciprofloxacin, and ofloxacin could reach 96.9, 88.2, 70.3, 83.5, and 88.1%, respectively. The initial pH, photocatalyst dosage, and initial concentration were comprehensively investigated for degrading malachite green. In addition, we also explored the prepared catalyst for the removal of malachite green from different actual wastewater samples. After three cycles, the degradation efficiency of malachite green by MIL-53-(Fe)/Sn3O4-5 decreased very little, exhibiting good reuse performance. The enhanced photodegradation efficiency of MIL-53-(Fe)/Sn3O4-5 could be attributed to the construction of heterojunctions derived from a compact joint interface between Sn3O4 and Fe-MOF, which expedited the separation ability of photogenerated carriers and broadened the visible response range. The active species trapping experiments and electron spin-resonance results determined that many active species (h+, •OH, and •O2–) were involved in the photocatalytic process. Correspondingly, a convincible photodegradation mechanism between Sn3O4 and MIL-53-(Fe) was proposed according to the experimental results. This study demonstrates that the fabricated Sn3O4 and MOF composites can provide a feasible solution for the purification of wastewater. [ABSTRACT FROM AUTHOR]

A novel SnO2 QDs (quantum dots)/PDI heterojunction photocatalyst was successfully constructed by a simple in‐situ compounded method and exhibited highly enhanced photocatalytic performance and long‐term stability under visible light irradiation. The results of ISI‐XPS and AFM‐KPFM revealed that the effective photo‐generated electrons transferred from PDI supramolecular nanorods to closely attached to SnO2 QDs, which was driven by a giant built‐in electric field across this hetero‐interface, thus highly improved the migration and separation of photo‐generated carriers. Importantly, we have proved for the first time that the formation of heterojunction can effectively hinder the generation of PDI anion radicals (PDI.−), thereby realized improved photocatalytic stability of PDI supramolecular aggregates by reducing the dissociation of PDI supramolecular caused by electrostatic repulsion interaction between PDI.− units. Furthermore, the established high structure and morphology stability also supported its excellent photocatalytic stability. [ABSTRACT FROM AUTHOR]

In this paper, the hydrangea-shaped Bi 2 WO 6 /ZIF-8 (BWOZ) visible light photocatalysts have been prepared via a facile synthetic strategy for the first time. The constructed BWOZ composites were systematically studied by a series of characterization techniques. The SEM results manifested the octahedral ZIF-8 coated the flower-like Bi 2 WO 6 uniformly and the composition of BWOZ composites had been confirmed by XPS measurement. And the photocatalytic activity was evaluated by eliminating methylene blue with the help of visible light. The results showed that 7%-BWOZ (7.0 wt% Bi 2 WO 6) exhibited better photodegradation capability than pure Bi 2 WO 6 and ZIF-8. Compared with Bi 2 WO 6 , the photocatalytic degradation of methylene blue by 7%-BWOZ could reach 85.7%. In addition, the pseudo-first-order kinetic constant of 7%-BWOZ was 23.00 and 1.61 times that of pristine Bi 2 WO 6 and ZIF-8, respectively. The improved photocatalytic ability of BWOZ systems may be due to the construction of heterojunctions between Bi 2 WO 6 and ZIF-8, which resulted in the rapid separation of photogenerated carriers. Additionally, the specific surface area of the formed BWOZ system was also improved in comparison with the flower-shaped Bi 2 WO 6 , and thus more active sites could be provided to contact with methylene blue molecules, thereby achieving better removal capacity. Moreover, trapping experiments and electron spin resonance results further illustrated that the coexistence of multiple free radicals realized efficient degradation of methylene blue. More importantly, the photocatalytic property of the 7%-BWOZ composite remained even after three cycles. Furthermore, a feasible photodegradation mechanism was also explored in depth. [Display omitted] • A novel photocatalyst of Bi 2 WO 6 /ZIF-8 was fabricated via a facile synthetic strategy. • The Bi 2 WO 6 /ZIF-8 can photodegrade methylene blue (MB) from wastewater efficiently. • The Bi 2 WO 6 /ZIF-8 can be applied in actual wastewater and possessed high renewability. • A convincible photocatalytic mechanism for removing MB by Bi 2 WO 6 /ZIF-8 was provided. [ABSTRACT FROM AUTHOR]

[Display omitted] • New MIL-53(Fe)@TiO 2 composites were fabricated via a one-pot solvothermal process. • The MIL-53(Fe)@TiO 2 = 1:2 showed boosted adsorption performance for tetracycline. • The MIL-53(Fe)@TiO 2 = 1:2 also displayed photocatalytic capability for tetracycline. • The synergism and active species (•O 2 − and •OH) enhanced the elimination ability. • A possible mechanism for tetracycline degradation by MIL-53(Fe)@TiO 2 was proposed. Novel semiconductor–MOFs composites based on TiO 2 and MIL-53(Fe) were constructed using a facile one-pot solvothermal process and acted as effective visible-light responsive adsorptive photocatalysts for the removal of tetracycline (TC). The resultant MIL-53(Fe)@TiO 2 composites were characterized by comprehensive analyses, ESR, and photoelectrochemical measurements. Experimental results showed that the synthesized MIL-53(Fe)@TiO 2 composites possessed enhanced adsorption and excellent photocatalytic activity for TC solution under visible light irradiation. Among all the composites, the MIL-53(Fe)@TiO 2 = 1:2 exhibited optimal removal performance compared with pristine MIL-53(Fe) and TiO 2. The results of UV–vis DRS verified the visible light absorption range of the prepared composite was improved, and the results of the Nyquist plot illustrated that the transfer ability of photo-generated charge carriers was boosted. More importantly, the ESR results showed that the •O 2 − and •OH active species played a crucial role in photocatalytic reactions. The enhanced photocatalytic ability was due to not only the fabrication of the n-n type heterojunction photocatalysts, which could provide more active species, but also the synergy between MIL-53(Fe) and TiO 2 in the composites. A possible reaction mechanism was proposed to elucidate the reason for the photocatalytic performance enhancement. Our findings may open up a new field for Fe-MOF and semiconductor composite materials in removing TC in visible light. [ABSTRACT FROM AUTHOR]

[Display omitted] • The principals and bases of PDI supramolecular photocatalysts were summarized and discussed. • Recent progresses in PDI–based supramolecular photocatalysts were comprehensively and critically reviewed. • Prospects for PDI–based photocatalysts were proposed. Perylene diimide (PDI) organic materials and their derivatives are currently one of the best n–type organic semiconductors. In recent years, PDI supramolecular photocatalysts have been reported to be able to independently complete the entire photocatalytic process from light absorption, carrier separation to catalytic reaction, which attracts many researchers' attention. However, its practical applications are still faced with huge challenges such as slow transfer of photogenerated electrons and holes, fast recombination of the above photogenerated carriers, low catalytic activity and poor stability. In order to address these problems, many scholars have carried out a lot of studies. Herein, we will present an up-to-date review on using PDI supramolecular photocatalysts as the main catalyst and corresponding investigations on improving its photocatalytic performance via monomer molecular design of PDI, building π-π composite system, semiconductor heterojunction, precious metal deposition, carbon material coupling, designing PDI polymer and synergy with other methods, etc., and summarize the current existing questions, and make a prospect for the future research. [ABSTRACT FROM AUTHOR]