Synergistic Enhancement of Electron Dynamics and Optical Properties in Zeolitic Imidazolate Framework-8-Derived Zinc Oxide via Surface Plasmon Resonance Effects of Silver Nanoparticles under UV Irradiation

This study investigates the surface plasmon resonance (SPR)-induced UV photoresponse of zinc oxide (ZnO) derived from zeolitic imidazolate framework-8 (ZIF-8) to assess the influence of silver nanoparticles (Ag NPs) on the photoresponse behavior of metal-organic framework (MOF)-derived ZnO. The initial synthesis involved a thermal treatment in air to convert ZIF-8 into ZnO. We noted enhanced optical absorption both in the UV and visible spectra with the deposition of Ag NPs onto the ZIF-8-derived ZnO. Additionally, the presence of Ag NPs in the ZnO resulted in a substantial increase in current, even without any light exposure. This increase is attributed to the transfer of electrons from the Ag NPs to the ZnO. Photocurrent measurements under UV illumination revealed that the photocurrent with Ag NPs was significantly higher-by two orders of magnitude-compared with that without Ag NPs. This demonstrates that SPR-induced absorption markedly boosted the photocurrent, although the current rise and decay time constants remained comparable to those observed with ZnO alone. Although Ag NPs contribute electrons to ZnO, creating a "pre-doping" effect that heightens baseline conductivity (even in the absence of light), this does not necessarily alter the recombination dynamics of the photogenerated carriers, as indicated by the similar rise and decay time constants. The electron transfer from Ag to ZnO increases the density of charge carriers but does not significantly influence their recombination.

A comprehensive review of oxygen vacancy modified photocatalysts: synthesis, characterization, and applications

Photocatalytic technology is a novel approach that harnesses solar energy for efficient energy conversion and effective pollution abatement, representing a rapidly advancing field in recent years. The development and synthesis of high-performance semiconductor photocatalysts constitute the pivotal focal point. Oxygen vacancies, being intrinsic defects commonly found in metal oxides, are extensively present within the lattice of semiconductor photocatalytic materials exhibiting non-stoichiometric ratios. Consequently, they have garnered significant attention in the field of photocatalysis as an exceptionally effective means for modulating the performance of photocatalysts. This paper provides a comprehensive review on the concept, preparation, and characterization methods of oxygen vacancies, along with their diverse applications in nitrogen fixation, solar water splitting, CO2 photoreduction, pollutant degradation, and biomedicine. Currently, remarkable progress has been made in the synthesis of high-performance oxygen vacancy photocatalysts and the regulation of their catalytic performance. In the future, it will be imperative to develop more advanced in situ characterization techniques, conduct further investigations into the regulation and stabilization of oxygen vacancies in photocatalysts, and comprehensively comprehend the mechanism underlying the influence of oxygen vacancies on photocatalysis. The engineering of oxygen vacancies will assume a pivotal role in the realm of semiconductor photocatalysis.

Nanotechnology-assisted treatment of pharmaceuticals contaminated water

The presence of pharmaceutical compounds in wastewater due to an increase in industrialization and urbanization is a serious health concern. The demand for diverse types of pharmaceutical compounds is expected to grow as there is continuous improvement in the global human health standards. Discharge of domestic pharmaceutical personal care products and hospital waste has aggravated the burden on wastewater management. Further, the pharmaceutical water is toxic not only to the aquatic organism but also to terrestrial animals coming in contact directly or indirectly. The pharmaceutical wastes can be removed by adsorption and/or degradation approach. Nanoparticles (NPs), such as 2D layers materials, metal-organic frameworks (MOFs), and carbonaceous nanomaterials are proven to be more efficient for adsorption and/or degradation of pharmaceutical waste. In addition, inclusion of NPs to form various composites leads to improvement in the waste treatment efficacy to a greater extent. Overall, carbonaceous nanocomposites have advantage in the form of being produced from renewable resources and the nanocomposite material is biodegradable either completely or to a great extent. A comprehensive literature survey on the recent advancement of pharmaceutical wastewater is the focus of the present article.

Construction of a direct Z-scheme CeO2/UiO-66-NH2 heterojunction for boosting photocatalytic organic pollutant degradation and H2 evolution performance

In this study, hollow CeO₂ nanospheres were grown on UIO-66-NH₂ nanosheets to form a novel CeO₂/UiO-66-NH₂ (abbreviation, CU_x) Z-scheme heterojunction photocatalyst by calcination and hydrothermal method for hydrogen production and photocatalytic degradation of organic pollutants. Under visible light, the H₂ generation rate of the CU_0.50 composite was 5662.1 μmol g^-1 h^-1, which was 22 and 7 fold than that of pure CeO₂ and pure UiO-66-NH₂, respectively. In addition, compared with CeO₂ and UiO-66-NH₂, the as-prepared CU_x composites exhibited enhanced photo-degradation efficiencies for tetracycline (TC) and 2,4-dichlorophenol (DCP) under simulated solar light irradiation. Among them, the CU_0.50 composite demonstrated the highest photocatalytic performance and reached 91.5% for TC, and 94.3% for DCP. In addition, a logical solid-state Z-type electron transfer mechanism is presented with the results of radical scavenging and ESR experiments to illustrate the intensive decomposed ability of the photocatalytic system. The enhanced photocatalytic performance of CU_x heterostructures can be attributed to the formation of a band-position-matched hollow structure heterojunction between CeO₂ and UIO-66-NH₂, which can effectively inhibit the recombination of carriers and increase the specific surface area as well as the light absorption. Moreover, the oxidation and reduction ability of the charge carriers was also increased. This work resulted in a feasible idea for removing organic pollutants and hydrogen production by traditional inorganic semiconductor/MOF-based heterostructured photocatalysts.

Metal-Organic Frameworks Meet Metallic Oxide on Carbon Fiber: Synergistic Effect for Enhanced Photodegradation of Antibiotic Pollutant

Photodegradation shows a potential strategy for alleviating the excessive antibiotics crisis. The synergistic effect of various metal compounds immobilized on conductive substrates has been considered for wastewater treatment. However, developing a facile and universal approach for rational design and enhancing photocatalytic properties has endured extreme challenges. Herein, we develop a strategy to facilitate the photocatalytic reactions by designing a composite architecture of ZIF-8 ligand binding to the in-situ synthesis ZnO seed layer on carbon fiber. In this architecture, the dissolution and release of the seed layer in the excessive 2-Methylimidazole methanol solution were used as the binder to enhance the interplay between organic ligand and substrate. As an evaluated system for antibiotic contaminants, the photodegradation of tetracycline hydrochloride was performed with a removal efficiency of 88.47% (TC = 50 mg/L, pH = 4, 0.08 g of photocatalyst, illumination within 100 min). Moreover, the photocatalyst exhibited a steady photocatalytic activity (75.0%) after five cycles. The present work demonstrated a strategy for enhancing the photocatalytic performances of carbon fiber and accordingly provided useful perception into the design of the synergistic structure.

Enhanced photocatalytic performance over PANI/NH2-MIL-101(Fe) with tight interfacial contact

Constructing a suitable heterojunction structure while maintaining a tight interface to promote the separation of photogenerated electrons is of great significance for improving the photocatalytic activity. In this paper, a new PANI/NH₂-MIL-101(Fe) II-scheme heterojunction was prepared by a hydrothermal method. PANI with a porous structure was firstly obtained by the template method, and then PANI fragments were loaded on the surface of NH₂-MIL-101(Fe) crystals under hydrothermal conditions to obtain a PANI/NH₂-MIL-101(Fe) photocatalyst. The photocatalytic degradation of TC under simulated sunlight can reach 90% within an hour, and the maximum hydrogen evolution rate is 7040 μmol g^-1 h^-1 under visible light. The enhanced catalytic performance of PANI/NH₂-MIL-101(Fe) was attributed to the appropriate matching of the VB and CB of PANI and NH₂-MIL-101(Fe), and secondly, the coordination bonds formed between PANI and NH₂-MIL-101(Fe) provided a channel for charge separation and transfer. Finally, a possible mechanism of the photocatalytic system was proposed through a free radical capture experiment and characterization analysis. More importantly, the experiment proved that the heterojunction formed by PANI and NH₂-MIL-101(Fe) can achieve the effect of complementing each other, which provides a feasible idea and method for the design of efficient heterojunction photocatalysts.

Nanoengineered metal-organic framework for adsorptive and photocatalytic mitigation of pharmaceuticals and pesticide from wastewater

Rapidly expanding water pollution has transformed into significant dangers around the world. In recent years, the pharmaceutical and agriculture field attained enormous progress to meet the necessities of health and life; however, discharge of trace amounts of pharmaceuticals and pesticides into water significantly have a negative influence on human health and the environment. Contamination with these pollutants also constitutes a great threat to the aquatic ecosystem. To deal with the harmful impacts of such pollutants, their expulsion has attracted researchers' interest a lot, and it became essential to figure out techniques suitable for the removal of these pollutants. Thus, many researchers have devoted their efforts to improving the existing technology or providing an alternative strategy to solve this environmental problem. One of the attractive materials for this purpose is metal-organic frameworks (MOFs) due to their superior high surface area, high porosity, and the tunable features of their structures and function. Among various techniques of wastewater treatment, such as biological treatment, advanced oxidation process and membrane technologies, etc., metal-organic frameworks (MOFs) materials are tailorable porous architectures and are viably used as adsorbents or photocatalysts for wastewater treatment due to their porosity, tunable internal structure, and large surface area. MOFs are synthesized by various methods such as solvo/hydrothermal, sonochemical, microwave and mechanochemical methods. Most common method used for the synthesis of MOFs is solvothermal/hydrothermal methods. Herein, this review aims at providing a comprehensive overview of the latest advances in MOFs and their derivatives, focusing on the following aspects: synthesis and applications. This review comprehensively highlights the application of MOFs and nano-MOFs to remove pharmaceuticals and pesticides from wastewater. For the past years, transition metal-based MOFs have been concentrated as photocatalyst/adsorbents in treating contaminated water. However, work on main group metal-based MOFs is not so abundant. Hence, the foremost objective of this review is to present the latest material and references concerning main group element-based MOFs and nanoscale materials derived from them towards wastewater treatment. It summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future. With the context of recent pioneering studies on main group elements-based MOFs and their derivatives; we hope to stimulate some possibilities for further development, challenges and future perspectives in this field have been highlighted.

MOF-5 derived ZnO-C nanoparticles combined with α-MnO2 for efficient degradation of tetracycline under visible light

A multifunctional α-MnO2/ZnO-C (MZ) Z-scheme photocatalyst was synthesized by suit-growth of α-MnO2 on the surface of MOF-5 and pyrolysis of the organic components in a certain condition. The obtained photocatalysts...

A review of metal organic framework (MOFs)-based materials for antibiotics removal via adsorption and photocatalysis

Antibiotic abuse has led to serious water pollution and severe harm to human health; therefore, there is an urgent need for antibiotic removal from water sources. Adsorption and photodegradation are two ideal water treatment methods because they are cheap, simple to operate, and reusable. Metal organic frameworks (MOFs) are excellent adsorbents and photocatalysts because of their high porosity, adaptability, and good crystal form. The aim of this study is to suggest ways to overcome the limitations of adsorption and photocatalysis treatment methods by reviewing previous applications of MOFs to antibiotic adsorption and photocatalysis. The different factors influencing these processes are also discussed, as well as the various adsorption and photocatalysis mechanisms. This study provides a valuable resource for researchers intending to use MOFs to remove antibiotics from water bodies.

Metal oxide integrated metal organic frameworks (MO@MOF): rational design, fabrication strategy, characterization and emerging photocatalytic applications

This review focuses on the possible synthesis route, characterization techniques, and mechanistic pathways involved in the photocatalytic applications of MO@MOFs.

A Fenton-like method using ZnO doped MIL-88A for degradation of methylene blue dyes

MIL-88A with different sizes was prepared by hydrothermal method by changing the content of ZnO. The samples were characterized by SEM, TEM, XRD, XPS and FT-IR. The synthesized material was used for the removal of methylene blue dye in a Fenton-like reaction, and the optimal reaction conditions were studied through single factor experiments. The experimental results show that when the molar ratio of the amount of ZnO introduced to FeCl3·6H2O is 1 : 1, the obtained materials have better catalytic performance than others. Under the optimal conditions, MIL-88A(Fe1Zn1) has the best catalytic performance for 300 mg L-1 methylene blue. The removal rate can reach 96.15% within 40 minutes.