Self-Assembly of a 3D Hollow BiOBr@Bi-MOF Heterostructure with Enhanced Photocatalytic Degradation of Dyes

Z-scheme Fe@Fe2O3/BiOBr heterojunction with efficient carrier separation for enhanced heterogeneous photo-Fenton activity of tetracycline degradation: Fe2+ regeneration, mechanism insight and toxicity evaluation

The recombination of photogenerated carrier leads to inefficient Fe2+ regeneration, which limits the extensive application of heterogeneous photo-Fenton. Here, a novel Fe@Fe2O3/BiOBr catalyst with Z-scheme heterojunction structure is designed, and the establishment of the Z-scheme heterojunction facilitates the separation and transfer of photogenerated carrier and maintains the superior redox capability of the system. As-prepared Fe@Fe2O3/BiOBr catalyst exhibits outstanding catalytic performance and stability, especially for the optimum composite FFB-3, its degradation efficiency of tetracycline (TC) achieves 98.22% and the mineralization degree reaches 59.48% within 90 min under natural pH. The preeminent catalytic efficiency benefited from the synergistic of heterogeneous photo-Fenton and Z-scheme carriers transfer mechanism, where Fe2+ regeneration was achieved by photogenerated electrons, and increased hydroxyl radicals were produced with the participation of H2O2 in-situ generated. The results of free-radical scavenging experiment and ESR illustrated that •OH, •O2-, 1O2 and h+ were active species participating in TC degradation. Furthermore, the TC degradation paths were proposed according to LC-MS, and the toxicity evaluation result showed that the toxicity of TC solutions was markedly decreased after degradation. This study provides an innovative strategy for heterogeneous photo-Fenton degradation of antibiotic contaminations by constructing Z-scheme heterojunctions.

Synthesis of a 3D Flower-Like BiOCl/Bi-MOF Heterostructure for High-Performance Removal of Rhodamine B and Tetracycline Hydrochloride

Semiconductor materials based on bismuth metal have been extensively explored for their potential in photocatalytic applications owing to their distinctive crystal structure. Herein, we present the development of a hybrid photocatalyst, CAU-17/BiOCl, featuring a flower-like nanosheet morphology tailored for the photocatalytic degradation of organic contaminants such as rhodamine B (RhB) and tetracycline hydrochloride (TCH). The composite material is obtained by growing thin CAU-17 layers directly onto the host flower-like BiOCl nanosheets under solvothermal conditions. The optimized CAU-17/BiOCl composite possesses excellent photocatalytic performance, achieving a notable 96.0% removal rate for RhB and 78.4% for TCH after 60 and 90 min of LED light irradiation, respectively. This boosted activity is attributed to the heightened absorption of visible light caused by BiOCl and the provision of additional reaction sites due to the thin CAU-17 layers. Furthermore, the establishment of an S-scheme heterojunction mechanism enables efficient charge separation between CAU-17 and BiOCl, facilitating the separation of photoinduced electrons (e-) and holes (h+). Analysis of the degradation mechanism of RhB and TCH reveals the predominant role of superoxide radicals (•O2-), e-, and h+ in the photocatalytic degradation process. Moreover, the removal efficiency of TCH can reach approximately 64.5% after four cycles of recycling of CAU-17/BiOCl. Our work provides a facile, effective solution and a theoretically explained approach for the effective degradation of pollutants using heterojunction photocatalysts.

In situ growth of Bi-MOF on cotton fabrics via ultrasonic synthesis strategy for recyclable photocatalytic textiles

Bismuth-based metal-organic framework (Bi-MOF) materials have shown potential for treating organic pollutants. In this work, multifunctional textiles were produced by in situ synthesis of CAU-17 on carboxymethylated cotton fabrics by solvothermal and ultrasonic strategies and employed as recyclable photocatalysts. The compositional and structural features of the dense MOF crystal coatings on cotton fibers were confirmed by scanning electron microscopy, X-ray diffraction, and other characterization approaches. Under optimized conditions, the developed functionalized cotton fabrics achieved a photodegradation efficiency of 98.8% under visible light for RhB in water, as well as good recyclability. The described results have provided the basis and reference for the fabrication of MOF-functionalized textiles.

Amino-grafted Biochar as a Novel Photocatalyst for degradation of high concentration dye

Photocatalytic degradation of organic pollution by biochar was a sustainable strategy for waste water remediation, nevertheless, it still suffers drawbacks like low efficiency due to the poor photocatalytic properties of pristine biochar. Herein, amino groups were grafted on the edge sites/defects of biochar by Friedel-Crafts acylation to enhance the degradation of high concentration dye solutions. The results suggested that the amino groups played an important role in imparting photocatalytic properties to biochar. Owing to the strong Lewis basicity and electron-donating ability of amino groups, their interaction with oxygen-containing functional groups/aromatic structures in biochar was improved, which enhanced the electron exchange ability of biochar under visible light irradiation, resulting in excellent degradation performances of high concentration RhB (∼10 times faster than ungrafted biochar). In this work, amino-grafted garlic peel biochar delivered a new idea for the future direction of biochar-based photocatalysis in wastewater remediation.

Ultrathin Layered Structure and Oxygen Vacancies Mediated Efficient Charge Separation toward High Photocatalytic Activity in BiOIO3 Nanosheets

Previous bismuth-based photocatalysts usually employ a strong acid solution (e.g., HNO3 solution) to obtain an ultrathin structure toward high photocatalytic activity. In this work, the ultrathin layered BiOIO3 nanosheets are successfully synthesized using just the glucose hydrothermal solution. The high-concentration glucose solution shows the obvious acidity after the hydrothermal process, which leads to the quick decrease in thickness of BiOIO3 nanosheets from ∼45.58 to ∼5.74 nm. The ultrathin structure can greatly improve charge carriers' separation and transfer efficiency. The generation of reductive iodide ions brings about oxygen vacancies in the ultrathin nanosheets, then the defect energy level is formed, causing the decreased band gap and improving the visible light absorption. Compared to thick BiOIO3 nanosheet with little oxygen vacancies, much higher carrier separation efficiency and visible light absorption are achieved in the ultrathin nanosheets with oxygen vacancies, resulting in an excellent photocatalytic performance (0.1980 min-1 for RhB degradation), which is much higher than most other bismuth-based photocatalysts. The superoxide radicals (•O2-) and holes (h+) are the major active species responsible for high photocatalytic activity. This work affords an environmentally friendly strategy to synthesize ultrathin photocatalysts with superior photocatalytic properties.

Swallowed Embedding of Nanopetal-Rich Microflowers in Flexible Photocatalytic and Thermoresponsive Functional Composite Fibers

Developing efficient catalysts to degrade pollutants in water is a very important way to alleviate water pollution. However, it is crucial but challenging to broaden the functions of conventional photocatalysts and improve their environmental adaptability. In this paper, Bi(Er3+/Yb3+)OBr/polyacrylonitrile (BOB-EY/PAN) composite fibers with a swallowed-embedded structure assembled with nanopetal-rich microflowers were designed and fabricated, integrating photocatalytic and temperature-monitoring functions simultaneously. Their unique structure brings a large specific surface area, and the doping of rare earth ions improves the separation efficiency of electron-hole pairs, which enhances the photocatalytic efficiency and endows the fibers with a temperature-monitoring function at the same time. Under simulated sunlight irradiation, the nanofibers show a maximum degradation efficiency of 99.2% for tetracycline hydrochloride (TC) with a degradation constant of K as high as 0.078 min-1. Based on the fluorescence intensity ratio (FIR), the two thermally coupled levels of Er3+ in the nanofibers, 2H11/2 and 4S3/2, provide real-time temperature feedback, displaying a maximum relative sensitivity as high as 0.0215 K-1 at 303 K. Dual-functional BOB-EY/PAN composite nanofibers show great potential for industrial wastewater disposition, providing solutions for wastewater purification in special scenarios.

Exposed {110} facets of BiOBr anchored to marigold-like MnCo2O4 with abundant interfacial electron transfer bridges and efficient activation of peroxymonosulfate

Precise charge transfer modification and efficient activation of peroxymonosulfate are effective methods for increasing photocatalytic efficiency. Here, BiOBr/MnCo2O4 photocatalysts with abundant Mn-Br bonds were generated by immobilizing the exposed {110} facets of BiOBr in the marigold-like MnCo2O4. The prepared BiOBr/MnCo2O4 retained the marigold-like morphology of MnCo2O4 while exhibiting good adsorption properties and interface contact effects. More importantly, the interfacial Mn-Br bond between MnCo2O4 and BiOBr functioned as charge transport bridges, allowing for a directional transfer channel and lowering the potential energy barrier for interfacial charge transfer. In addition, the exposure of the {110} facets exhibited more Mn atom-anchored sites for easy anchoring of BiOBr, significantly solving the stability problem of the bismuth material. Compared to MnCo2O4 + BiOBr, which did not form Mn-Br bonds, the MnCo2O4/BiOBr heterojunction had more efficient photocatalytic activity (1.3 times) and stability. This suggested that using electronic bridges for directional charge transfer was an efficient way to improve photocatalytic efficiency.

Removal of dyes using polymers of intrinsic microporosity (PIMs): a recent approach

Removal of dyes from various industrial effluents is a great challenge, and cost-effective methods and materials with high dye removal efficacy are in high demand. Adsorption, nanofiltration and photocatalytic degradation are three major techniques that have been investigated for dye removal. PIMs are promising materials for use in these three methods based on their attributes, such as microporosity, solution processibility, high chemical stability and tunability through facile synthesis and easy postmodification. Although the number of reports on dye removal employing PIMs are limited, some of the materials have been shown to exhibit good dye separation properties, which are comparable to those of the state-of-the-art material activated carbon. In this highlight, we make an account of progress in PIMs and PIM-based composite materials in different dye removal processes over the last decade. Furthermore, we discuss the existing challenges of PIM-based materials and aim to analyze the key parameters for improving their dye removal properties.

Metal-organic frameworks for wastewater treatment: Recent developments, challenges, and future prospects

Wastewater treatment is critically important for the existence of life on earth; however, this approach involves the removal of toxic metal contaminants and organic pollutants, requiring efficient adsorbent materials. Within this agenda, metal-organic frameworks (MOFs) appear to be potential materials due to their unique properties as efficient adsorbents, effective photocatalysts, and reliable semi-permeable membranes. Therefore, MOFs have undergone various modifications over the years without desirable success to improve adsorption capacity, hydro-stability, reaction kinetics, and reusability. Therefore, scientists around the world got engaged in MOF research for novel modifications, including defect engineering, carbonization, and membrane fabrication, at the laboratory scale. This review focuses on developing MOF-based adsorbents, photocatalysts, and semi-permeable membranes for wastewater treatment since 2015, emphasizing their structural-functional relationships. Finally, the challenges and opportunities with MOFs in wastewater treatment are also underlined for future efforts.

Bi/Mn-Doped BiOCl Nanosheets Self-Assembled Microspheres toward Optimized Photocatalytic Performance

Doping engineering of metallic elements is of significant importance in photocatalysis, especially in the transition element range where metals possess empty 'd' orbitals that readily absorb electrons and increase carrier concentration. The doping of Mn ions produces dipole interactions that change the local structure of BiOCl, thus increasing the specific surface area of BiOCl and the number of mesoporous distributions, and providing a broader platform and richer surface active sites for catalytic reactions. The combination of Mn doping and metal Bi reduces the forbidden bandwidth of BiOCl, thereby increasing the absorption in the light region and strengthening the photocatalytic ability of BiOCl. The degradation of norfloxacin by Bi/Mn-doped BiOCl can reach 86.5% within 10 min. The synergistic effect of Mn doping and Bi metal can change the internal energy level and increase light absorption simultaneously. The photocatalytic system created by such a dual-technology combination has promising applications in environmental remediation.

Constructing BiOBr1-xIx-y with Abundant Surface Br Vacancies for Excellent Visible-Light Photodegradation Capability of High-Concentration Refractory Contaminants

Bismuth oxybromide (BiOBr) is a promising photocatalytic semiconductor material due to its unique hierarchical structure and band structure. However, its photocatalytic applications are restricted due to its narrow visible-light absorption range and poor photooxidation capability. In this study, BiOBr1-xIx-y with rich surface Br vacancies (BrVs-rich BiOBr1-xIx-y) was created via a facile indirect substitution strategy. Benefiting from the broadened visible-light response range and reduced recombination rate of photogenerated carriers, BiOBr1-xIx-y shows excellent visible-light photodegradation ability for high-concentration refractory contaminants, such as phenol, tetracycline, bisphenol A, rhodamine B, methyl orange, and even real wastewater. At the same time, the Br vacancies can regulate the band structure of BiOBr1-xIx-y and serve as trap states to promote charge separation, thus facilitating surface photoredox reactions. An in-depth investigation of the Br vacancy effect and photodegradation mechanism was conducted. This novel study revealed the significance of Br vacancies in enhancing the photocatalytic performance of BiOBr under visible light, providing a promising strategy for improving the utilization efficiency of sunlight in wastewater treatment.

Applications of BiOX in the Photocatalytic Reactions

BiOX (X = Cl, Br, I) families are a kind of new type of photocatalysts, which have attracted the attention of more and more researchers. The suitable band gaps and their convenient tunability via the change of X elements enable BiOX to adapt to many photocatalytic reactions. In addition, because of their characteristics of the unique layered structure and indirect bandgap semiconductor, BiOX exhibits excellent separation efficiency of photogenerated electrons and holes. Therefore, BiOX could usually demonstrate fine activity in many photocatalytic reactions. In this review, we will present the various applications and modification strategies of BiOX in photocatalytic reactions. Finally, based on a good understanding of the above issues, we will propose the future directions and feasibilities of the reasonable design of modification strategies of BiOX to obtain better photocatalytic activity toward various photocatalytic applications.

Au@NiFeMOFs as the signal quencher of Au@g-C3N4NSs composite for sensitive "on-off" electrochemiluminescence immunosensing of beta-2-microglobulin

In this study, an electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor was constructed to detect beta-2-microglobulin (B2M). As a donor-acceptor pair, a carbon nitride nanosheet modified with gold nanoparticles (Au@g-C₃N₄NSs) and a nickel- and iron-based organic framework modified with gold nanoparticles (Au@NiFeMOFs) were prepared. The sandwich immunosensor was successfully constructed so that ECL-RET occurred between Au@NiFeMOFs and Au@g-C₃N₄NSs. The ECL intensity of the immunosensor decreased with the increase the B2M concentration due to the low conductivity of B2M. The linear range of the ECL-RET immunosensor was from 10 fg/mL to 10 ng/mL, and the limit of detection was 2.3 fg/mL (S/N = 3). The developed immunosensor had high sensitivity, high specificity, and excellent stability. It could realize the sensitivity test of B2M and provide a novel idea for the detection of biomarkers.

Omnidirectionally irradiated three-dimensional molybdenum disulfide decorated hydrothermal pinecone evaporator for solar-thermal evaporation and photocatalytic degradation of wastewaters

Although most solar steam generation devices are effective in desalinating seawater and purifying wastewaters with heavy metal ions, they are ineffective in degrading organic pollutants from wastewaters. Herein, we design novel solar-driven water purification devices by decoration of three-dimensional pinecones with MoS₂ nanoflowers via a one-step hydrothermal synthesis for generating clean water. The vertically arrayed channels in the central rachis and the unique helically arranged scales of the hydrothermal pinecone can not only transfer bulk water upward to the evaporation surface, but also absorb more solar light from different incident angles for solar-thermal evaporation and photodegradation of wastewaters under omnidirectional irradiations. The decorated MoS₂ nanoflowers can not only enhance the solar-thermal energy conversion efficiency, but also decompose organic pollutants in the bulk water by their photocatalytic degradation effects. The resultant hydrothermal pinecone with in situ decorated MoS₂ (HPM) evaporator exhibits a high evaporation rate of 1.85 kg m^-2 h^-1 under 1-sun irradiation with a high energy efficiency of 96 %. During the solar-driven water purification processes, the powdery HPM can also photodegrade organic pollutants of methylene blue and rhodamine B with high removal efficiencies of 96 % and 95 %, respectively. For practical demonstration, by floating in the methylene blue solution under 1-sun irradiation, the bulky HPM can generate clean water by simultaneous solar-thermal evaporation and photocatalytic degradation. The integration of solar steam generation and photocatalytic degradation mechanisms makes the HPM evaporator highly promising for practical high-yield purification of wastewaters.

The Solid-State Synthesis of BiOIO3 Nanoplates with Boosted Photocatalytic Degradation Ability for Organic Contaminants

BiOIO₃ exhibits excellent oxidation capacity in the photocatalytic degradation of contaminants thanks to its unique polarized electric and internal electrostatic field. However, the synthetic method of BiOIO₃ nanomaterials is mainly focused on hydrothermal technology, owing to its high energy consumption and time-consuming nature. In this work, a BiOIO₃ nanosheet was prepared by a simple solid-state chemical reaction, which was identified by XRD, EDS, XPS, and HRTEM. Benefiting from the strong oxidation ability of the valence band maximum, the distinctive layer structure, and the promoted generation of ·O₂^-, the BiOIO₃ nanosheet exhibits excellent photo-degradation activity for methyl orange (MO) and its apparent rate constant is 0.2179 min^-1, which is about 3.02, 8.60, and 10.26 times higher than that of P25, BiOCl, and Bi₂O₂CO₃, respectively. Interestingly, the BiOIO₃ nanosheet also has good photocatalytic degradation performance for phenolic compounds; in particular, the degradation rate of BPA can reach 96.5% after 16 min, mainly due to hydroxylation reaction.

Enhancing the durability of Au clusters in CO2 photoreduction via encapsulation in Cu-based metal-organic frameworks

Here, we report the encapsulation of Au₂₅ nanoclusters in a Cu₃(BTC)₂ metal-organic framework (Au₂₅@Cu-BTC), which can achieve CO₂ photoreduction for selective CO production in a gas-solid reaction system at low-concentration CO₂ atmospheres (even to 0.1%), with remarkably enhanced durability up to at least 48 h.

In Situ Growth of Cs3Bi2Br9 Quantum Dots on Bi-MOF Nanosheets via Cosharing Bismuth Atoms for CO2 Capture and Photocatalytic Reduction

Given the global warming caused by excess CO₂ accumulation in the atmosphere, it is essential to reduce CO₂ by capturing and converting it to chemical feedstock using solar energy. Herein, a novel Cs₃Bi₂Br₉/bismuth-based metal-organic framework (Bi-MOF) composite was prepared via an in situ growth strategy of Cs₃Bi₂Br₉ quantum dots (QDs) on the surface of Bi-MOF nanosheets through coshared bismuth atoms. The prepared Cs₃Bi₂Br₉/Bi-MOF exhibits bifunctional merits for both the high capture and effective conversion of CO₂, among which the optimized 3Cs₃Bi₂Br₉/Bi-MOF sample shows a CO₂-CO conversion yield as high as 572.24 μmol g^-1 h^-1 under the irradiation of a 300 W Xe lamp. In addition, the composite shows good stability after five recycles in humid air, and the CO₂ photoreduction efficiency does not decrease significantly. The mechanistic investigation uncovers that the intimate atomic-level contact between Cs₃Bi₂Br₉ and Bi-MOF via the coshared atoms not only improves the dispersion of Cs₃Bi₂Br₉ QDs over Bi-MOF nanosheets but also accelerates interfacial charge transfer by forming a strong bonding linkage, which endows it with the best performance of CO₂ photoreduction. Our new finding of bismuth-based metal-organic framework/lead-free halide perovskite by cosharing atoms opens a new avenue for a novel preparation strategy of the heterojunction with atomic-level contact and potential applications in capture and photocatalytic conversion of CO₂.

In situ fabrication of MIL-68(In)@ZnIn2S4 heterojunction for enhanced photocatalytic hydrogen production

Metal-organic frameworks (MOFs), as a class of semiconductor-like materials, are widely used in photocatalysis. However, the limited visible light absorption and poor charge separation efficiency are the main challenges restricting their photocatalytic performance. Herein, the type II heterojunction MIL-68(In)@ZIS was successfully fabricated by in situ growth of ZnIn₂S₄ (ZIS) on the surface of a representative MOF, i.e. MIL-68(In). After composition optimization, MIL-68(In)-20@ZIS shows an extraordinary photocatalytic hydrogen production efficiency of 9.09 mmol g^-1 h^-1 and good photochemical stability, which far exceeds those of most photocatalysts. The hierarchical loose structure of MIL-68(In)-20@ZIS is conducive to the adsorption of reactants and mass transfer. Meanwhile, a large number of tight 2D contact interfaces significantly reduce the obstruction of charge transfer, paving the way for high-perform photocatalytic hydrogen evolution. The experimental results demonstrate that the MIL-68(In)@ZIS heterojunction achieves intensive photoresponse and effective charge separation and transfer benefiting from unique charge transport paths of a type II heterojunction. This study opens an avenue toward MOF-based heterojunctions for solar energy conversion.

High-Performance Integrated rGO-[Polymeric Ionic Liquid] [Heteropolyanions] for Catalytic Degradation of Azo Dyes

Polymeric ionic liquid (such as poly[ViEtIm]Br)-modified reduced graphene oxide (rGO), rGO-poly[ViEtIm]Br, was nominated as an open carrier to construct a degradation platform. The large specific surface of rGO together with the anion-exchange property of poly[ViEtIm]Br terminals led to the wide growth of heteropolyanions (like [PW₁₂O₄₀]^3-, [PMo₁₂O₄₀]^3-, and [SiW₁₂O₄₀]^4-), thus assembling the integrated catalyst rGO-poly[ViEtIm][heteropolyanions]. The grafted poly[ViEtIm]Br provided an anchor point to interlink the polar heteropolyanions and the nonpolar rGO substrate, endowing this graphene-based catalyst with excellent dispersibility. The adequate exposure of heteropolyanions further promoted the decolorization capability during the degradation procedure. Morphology, structure, and properties of materials were confirmed and monitored via transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, etc. rGO-poly[ViEtIm][PW₁₂O₄₀] was selected as the optimal catalyst with degradation efficiency toward methyl orange reaching 98.7% in 3 h. In addition, the excellent structural stability of the catalyst improved the decolorization efficiency, which reached 95% after recycling five times.

Construction of BiOCl/Ti-MOFs type-II heterojunction photocatalyst for enhanced photocatalytic performance for multiple antibiotics removal

The increased threats to environmental and human health caused by the widespread use of antibiotics have increased the need for efficient technologies for removing antibiotic remnants from wastewater after production. Photocatalysis, which is non-toxic, highly efficient, and low energy consumption, has played a vital role in wastewater treatment among the aforementioned technologies. Therefore, a MIL-125(Ti)/BiOCl type-II heterojunction photocatalyst was fabricated using solvothermal method. Investigations remarkably revealed that the enhanced photocatalytic performance of the photocatalyst for multiple antibiotics degradation (tetracycline and ofloxacin) was attributed to the construction of a heterojunction, which inhibits carrier recombination and enhances visible-light absorption. Furthermore, the radical trapping experiments and electron spin resonance determined superoxide radicals and holes to be the main species in the photocatalytic process. Finally, we presented a potential photocatalytic mechanism that could account for the observations. Overall, this study offered guidelines for developing more photocatalysts with visible-light responses and removing multiple antibiotics from water more efficiently.

Reduced graphene oxide/carbon nitride composite sponge for interfacial solar water evaporation and wastewater treatment

Interfacial solar-driven steam generation has been proposed as a cost-effective green sustainable technology to alleviate the freshwater crisis. However, the desire to produce clean water from water sources containing organic contaminants is still remains a challenge due to the limitations of the traditional wastewater treatment methods. Here, we constructed a g-C3N4-based composite sponge solar steam generator (rGCPP) by a simple hydrothermal reaction. Benefiting from its low cost and easy preparation, this evaporator can be expected to be a promising candidate for the alleviation of water shortages and water pollution in practical applications. By combination of the solar steam generation and the photocatalysis into the rGCPP-based interfacial solar-driven steam generation system, the resulted rGCPP-based solar steam generator performs outstanding solar absorption of 90.8%, which achieves high evaporation rate of 1.875 kg m-2 h-1 and solar-to-vapor efficiency of 81.07% under 1 sun irradiation. Meanwhile, organic pollutants in the water source can be completely removed by photocatalytic degradation and the degradation rates were measured to be 99.20% for methylene blue and 91.07% for rhodamine B, respectively. Consequently, the as-prepared composite sponge has promising applications in generating clean water and alleviating water pollution.

In Situ Implantation of Bi2S3 Nanorods into Porous Quasi-Bi-MOF Architectures: Enabling Synergistic Dissociation of Borohydride for an Efficient and Fast Catalytic Reduction of 4-Nitrophenol

Catalytic hydrogenation reduction based on sodium borohydride (NaBH₄) has gained attention as an appealing "one-stone-two-birds" approach for the simultaneous elimination of nitroaromatic pollutants and the production of high-value aminoaromatics under mild conditions. However, the slow kinetics of NaBH₄ dissociation on the surface of catalysts restrict the catalytic hydrogenation reduction efficiency. Herein, we report an intelligent localized sulfidation strategy for an in situ implantation of Bi₂S₃ nanorods within quasi-Bi-MOF architectures (Bi₂S₃@quasi-Bi-MOF) by fine-tuning the pyrolysis temperature. In this novel Bi₂S₃@quasi-Bi-MOF, the porous quasi-Bi-MOF enables efficient adsorption of BH₄^- and 4-nitrophenol (4-NP), while Bi₂S₃ facilitates the BH₄^- dissociation to form H_ads* species adsorbed on the catalyst surface. Benefiting from the synergistic structure, Bi₂S₃@quasi-Bi-MOF exhibits excellent performance for the catalytic reduction of 4-NP, delivering a high turnover frequency (TOF) of 1.67 × 10^-4 mmol mg^-1 min^-1 and an extremely high normalized rate constant (k_nor) of 435298 s^-1 g^-1. The kinetic analysis and electrochemical tests indicate that this catalytic hydrogenation reduction follows the Langmuir-Hinshelwood mechanism. This study enriches the synthetic strategy of MOF-based derivatives and offers a new catalytic platform for hydrogenation reduction reactions.

High performance visible light response of a Z-type Bi2WO6/BiOBr/RGO heterojunction photocatalyst for the degradation of norfloxacin

A Bi₂WO₆/BiOBr/RGO (BWO/BOB/RGO) composite photocatalyst with a Z-type heterojunction was prepared by a simple one-pot hydrothermal method, and the micro-morphology and physicochemical properties of the prepared samples were characterized. After reacting under visible light for 120 min, the degradation rate of 20 mg L^-1 norfloxacin (NOR) by BWO/BOB/RGO was 95.12%, and the kinetic constant of the reaction was 6.42 times higher than that of pure BiOBr. Furthermore, BWO/BOB/RGO also shows good recycling stability and universality. The characterization results show that the improvement of the photocatalytic performance of the catalyst is mainly due to the heterojunction formed between Bi₂WO₆, RGO and BiOBr, which enhances the visible light absorption ability, accelerates the photogenerated electron migration and improves the electron-hole pair separation efficiency. The introduction of Bi₂WO₆ and RGO into the catalyst also increased its specific surface area and made it have more surface-active sites. The results of radical capture experiments showed that ˙O₂^- and h⁺ played an important role in the BWO/BOB/RGO reaction system, and the intermediate products and possible degradation pathways of the system were detected and analyzed. Furthermore, the electron transfer mechanism of the Z-type heterojunction using RGO as an electron transport medium and the mechanism of photocatalytic degradation of norfloxacin were proposed.

Modular Construction of an MIL-101(Fe)@MIL-100(Fe) Dual-Compartment Nanoreactor and Its Boosted Photocatalytic Activity toward Tetracycline

Iron-based metal-organic frameworks (MOFs) have aroused extensive concern as prospective photocatalysts for antibiotic (e.g., tetracycline, TC) degradation. However, efficiencies of single and simple Fe-based MOFs still undergo restricted light absorption and weak charge separation. Assembly of different iron-based MOF building blocks into a hybrid MOF@MOF heterostructure reactor could be an encouraging strategy for the effective capture of antibiotics from the aqueous phase. This paper reports a new-style MIL-101(Fe)@MIL-100(Fe) photocatalyst, which was groundbreakingly constructed to realize a double win for boosting the performances of adsorption and photocatalysis. The optical response range, surface open sites, and charge separation efficiency of MIL-101(Fe)@MIL-100(Fe) can be regulated through accurate design and alteration. Attributed to the synergistic effects of double iron-based MOFs, MIL-101(Fe)@MIL-100(Fe) exhibits an excellent photocatalytic activity toward TC degradability compared to MIL-101(Fe) and MIL-100(Fe), which is even superior to those reported previously in the literature. Furthermore, the main active species of •O₂^- and h⁺ were proved through trapping tests of the photocatalytic process. Additionally, MIL-101(Fe)@MIL-100(Fe) possesses remarkable stability, maintaining more than 90% initial photocatalytic activity after the fifth cycle. In brief, MIL-101(Fe)@MIL-100(Fe) was highly efficient for TC degradation. Our work offers a new strategy for visible-light photodegradation of TC by exploring the double Fe-based MOF composite.

RhB-Embedded Zirconium-Biquinoline-Based MOF Composite for Highly Sensitive Probing Cr(VI) and Photochemical Removal of CrO42-, Cr2O72-, and MO

How to accurately detect and efficiently sweep Cr(VI) from contaminated water has come into focus. Zirconium-based metal-organic frameworks (MOFs) play vital roles in water environmental chemistry due to excellent hydrolysis-resistant stability. However, as photochemical probes and photocatalysts, poor performances in detection sensitivity, selectivity, and photosensitiveness limit sole Zr-MOFs' applications. So, it is urgent to quest valid strategies to break through the dilemmas. Embedding luminous dyes into MOFs has been considered one of the most feasible avenues. Herein, a dual-emissive RhB@Zr-MOF with orange-yellow fluorescence has been assembled by in situ-encapsulating rhodamine B (RhB) into a zirconium-biquinoline-based MOF. Actually, within RhB@Zr-MOF, the aggregation fluorescence quenching (ACQ) effect of RhB molecules was effectively avoided. Notably, RhB@Zr-MOF exhibits a rapid fluorescence quenching response toward Cr(VI) ions with high selectivity, sensitivity, and anti-interference abilities. More interestingly, unlike the most widely reported fluorescence resonance energy transfer (FRET) between MOFs and encapsulated guest modules, photoinduced electron transfer from RhB to Zr-MOF has been confirmed by modeling the ground state and excited states of RhB@Zr-MOF using density functional theory (DFT) and time-dependent DFT (TD-DFT). The effective electron transfer makes RhB@Zr-MOF more sensitive in probing Cr₂O₇^2- and CrO₄^2- ions with ultralow detection limit (DL) values of 6.27 and 5.26 ppb, respectively. Prominently, the detection sensitivity based on DL values has been increased about 6 and 9 times, respectively, compared with pristine Zr-MOF. Moreover, rather negative CB and positive VB potentials make RhB@Zr-MOF have excellent photochemical scavenging ability toward Cr(VI) and MO.

Hollow CuFe2O4/MgFe2O4 Heterojunction Boost Photocatalytic Oxidation Activity for Organic Pollutants

P-n heterojunction-structured CuFe2O4/MgFe2O4 hollow spheres with a diameter of 250 nm were synthesized using a template-free solvothermal method, and time-dependent morphological studies were carried out to investigate the hollow formation mechanism. The CuFe2O4/MgFe2O4 with a molar ratio of 1:2 (Cu:Mg) had the highest degradation efficiency with the model organic dye Acid Orange 7, with a degradation rate of 91.96% over 60 min. The synthesized CuFe2O4/MgFe2O4 nanocomposites were characterized by XRD, TEM, HRTEM, UV-vis spectroscopy, Mott–Schottky, and EIS. Due to the synthesis of the p-n heterojunction, CuFe2O4/MgFe2O4 has efficient photogenerated carriers, and the hollow structure has a higher specific surface area and stronger adsorption capacity, which is significantly better than that of CuFe2O4 and MgFe2O4 in terms of photocatalytic performance. The outstanding performance shows that the p-n heterostructure of CuFe2O4/MgFe2O4 has potential for application in wastewater degradation.

Self-Assembled Zeolitic Imidazolate Framework/CdS Hollow Microspheres with Efficient Charge Separation for Enhanced Photocatalytic Hydrogen Evolution

Enhanced interfacial charge separation is of great importance to high-efficiency photocatalytic hydrogen production. Herein, we successfully fabricated novel ZIF-67/CdS hollow sphere (HS) and ZIF-8/CdS HS heterostructures through an in situ self-assembly process, in which ZIF-67 and ZIF-8 are closely coated on CdS HSs to form "double-shell"-like structures. This hierarchical heterostructure with porous outer layers on the surface of CdS HSs can expose accessible active sites and possess close contact. Upon visible-light illumination, the optimal proportion of ZIF-67/CdS HS displays a hydrogen generation rate of 1721 μmol g^-1 h^-1, which is 11.9 and 3.1 times higher than that of a pure CdS HS (145 μmol g^-1 h^-1) and ZIF-8/CdS HS (555 μmol g^-1 h^-1), respectively. The proposed photocatalytic mechanism is explored: ZIF-8/CdS HS follows the type-II mechanism, and ZIF-67/CdS HS follows the Z-scheme mechanism. The reason for the higher photocatalytic activity of ZIF-67/CdS HS is that ZIF-67 not merely with a porous structure facilitates the diffusion of H₂ gas, but with a well-matched band structure promotes charge transfer and separation.

Conductive polymer mediated earth abundant Z-scheme g-C3N4/Fe2O3 heterostructure with excellent photocatalytic activity

Being the second most abundant metal in the surface of the earth (5.1%), the size confined iron-based photocatalyst is of especially importance for solar energy conversion. Herein, the ternary Z-scheme...

Hematite nanoparticles decorated nitrogen-doped reduced graphene oxide/graphitic carbon nitride multifunctional heterostructure photocatalyst towards environmental applications

The carcinogenic heavy metals and aromatic organic compounds linger as wastewater pollutants implying great menace to the ecological balance. To solve these environmental pollution problems, the photocatalytic process is an...