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In pursuit of advancing photocatalysts for superior performance in water treatment and clean energy generation, researchers are increasingly focusing on layered double hydroxides (LDHs) which have garnered significant attention due to their customizable properties, morphologies, distinctive 2D layered structure and flexible options for modifying anions and cations. No review has previously delved specifically into ZnCr and NiCr LDH-based photocatalysts and therefore, this review highlights the recent surge in ZnCr and NiCr-based LDHs as potential photocatalysts for their applications in water purification and renewable energy generation. The structural and fundamental characteristics of layered double hydroxides and especially ZnCr-LDHs and NiCr-LDHs are outlined. Further, the various synthesis techniques for the preparation of ZnCr-LDHs, NiCr-LDHs and their composite and heterostructure materials have been briefly discussed. The applicability of ZnCr-LDH and NiCr-LDH based photocatalysts in tackling significant issues in water treatment and sustainable energy generation is the main emphasis of this review. It focuses on photocatalytic degradation of organic pollutants in wastewater, elucidating the principles and advancements for enhancing the efficiency of these materials. It also explores their role in H 2 production through water splitting, conversion of CO 2 into valuable fuels and NH 3 synthesis from N 2 , shedding light on their potential for clean energy solutions. The insights presented herein offer valuable guidance for researchers working towards sustainable solutions for environmental remediation and renewable energy generation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Microplastics (MPs), as emerging pollutants, have attracted the attention of environmentalists, statespersons, and the scientific community over the last few decades. To address the spread of MPs in the environment, it is imperative to develop various removal techniques and materials that are effective, scalable, and ecologically benign. However, to the best of our knowledge, no review has systematically examined the removal of MPs using adsorption or provided an in-depth discussion on various adsorbents. Adsorption is an inexpensive and effective technology for wastewater treatment. Recently, many researchers have conducted studies on MP remediation using diverse adsorbent materials, such as biochar, activated carbon, sponges, carbon nanotubes, metal-layered oxides, metal-organic frameworks (MOFs), and zeolites. Each adsorbent has advantages and disadvantages. To overcome their disadvantages, researchers have been designing and developing hybrid adsorbents for MP remediation. This review provides insights into these individual adsorbents and also discusses hybrid adsorbents for MP removal. Finally, the review elaborates on future possibilities and ways to enable more efficient, scalable, and environmentally friendly MP cleanup. Overall, this review bridges the gap between contemporary MP remediation using adsorption techniques and adsorbent development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Since the growing need for fuel is causing major harm to the environment, it is essential to introduce photocatalytic energy conversion devices that are safe for the environment. One such strategy is the utilisation of photocatalytic water-splitting devices to achieve sustainable hydrogen production. In order for these devices to operate optimally, it is imperative to utilise materials that possess the capability to properly capture sunlight. Porphyrins are significant molecules that can be found all over nature as units that absorb visible light. Energy conversion devices can benefit from porphyrins' multifunctional features, including their easy fabrication, excellent chemical constancy, plentiful metallic active sites, adaptable crystalline structure, and high specific surface area. They can produce charge-transfer excited states with or without a cocatalyst and make it easier to transfer energy and move rapid excited energy. These properties, along with their ease of synthesis, make them excellent starting materials for porous metal-organic framework-based photocatalysts that convert solar energy into usable fuels. This article provides an overview of the synthesis as well as designing of porphyrin-based MOFs. The effect of metal in porphyrin besed MOFs and two bridging ligands are summarized briefly. In this article, the photocatalytic applications of porpyrin based MOFs and composites as photocatalysts, such as the hydrogen evolution process and photodegradation of organic contaminants are discussed. In conclusion, the bottlenecks that need to be overcome and some potential solutions for the ongoing research and development of porphyrin-based MOF photocatalysts are discussed. [Display omitted] • Porphyrin-based MOFs as photo-active materials for photocatalysis are discussed. • Synthesis strategies for Porphyrin MOF composite photocatalysts are discussed. • Comprehensive breakdown of various bridging ligand types is provided. • Strategies for boosting photocatalytic performance are summarized. • Advances for H 2 evolution and water treatment research hotspots are summarized. [ABSTRACT FROM AUTHOR]

We report the fabrication of a novel waste-derived biochar-impregnated Bi 5 O 7 Br/Fe 3 O 4 (WBF) magnetic composite for photocatalytic removal of malachite green pollutant. The newly prepared catalyst was applied for the removal of malachite green dye under visible light irradiation. It was found that the composite degrades 99.39% MG dye within 20 min of the experiment as compared to Bi 5 O 7 Br, Fe 3 O 4, and biochar with 83.19%, 75.09%, and 55.47% in the 50-min experiment. The findings demonstrated that a photocatalytic integrated composite quickly transfers charges across surfaces and effectively separates electron-hole pairs, considerably increasing charge carrier separation and photocatalytic activity. Further, the kinetics show that the rate constant for WBF composite is 7.1 times higher than that observed for Bi 5 O 7 Br. Scavenging experiments reveal the huge role of.OH and •O 2 − radicals in malachite green degradation. Additionally, the magnetic nature of the catalyst ensures the easy separation of the catalyst during photocatlytic experiments and reduces the chance of secondary pollution. The results showed that integrating Bi 5 O 7 Br and biochar with Fe 3 O 4 to create photocatalytic composites is a very efficient strategy to boost photocatalytic activity for environmental waste water treatment. [Display omitted] • Newly designed waste derived bio-char impregnated Bi 5 O 7 Br/Fe 3 O 4 magnetic composite was successfully synthesised. • Composite degrades 99.39% MG dye within 20 min of the experiment. • Rate constant for MG removal for WBF composite is 7.1 times higher than that observed for Bi 5 O 7 Br. • Integrated composite improves the charge carrier separation and photocatalytic activity. • Composite exhibit sound stability upto six degradation cycles. [ABSTRACT FROM AUTHOR]

Growing industrialization and urbanization generate greater quantities of wastewater, which is constantly thrown into the surroundings. A number of dangerous contaminants like heavy metals, dyes, pesticides, antibiotics, and microbes are discharged into aquatic environments. Around the world, more than 80% of wastewater is discharged into the environment without being adequately treated. While environmental pollution is still increasing because of the increased percentage of polluting sectors, traditional methods of cleaning the environment are ineffective and costly. Recently, research has concentrated on designing 2D nanomaterials for environmental applications. MXenes and MXene based materials have drawn considerable interest and are now being investigated as novel substrate materials for a variety of applications because of their tuneable interlayer spacing and tailorable surface chemistry. This review discusses the fabrication methods, characterization methods, MXene derived materials, functionalization, toxicity, the multifunctional role of MXene, and applications of MXene based materials for CO 2 reduction, H 2 generation, and wastewater treatment systems. There are also multiple viewpoints on issues and future studies in this field that are addressed. [Display omitted] • The advance of MXene-based nanomaterials for water decontamination and energy conversion application are summarized. • The toxicity, multifunctional role, and fabrication of MXene based materials are introduced. • The reduction of CO 2 and H 2 generation is explained. • The elimination of heavy metals, dyes, antibiotic, and pesticides are determined. [ABSTRACT FROM AUTHOR]

To address the global energy crisis and widespread environmental deterioration issues, semiconductor photocatalysts have been widely recognized and studied. In this direction, new-age materials as zeolitic imidazolate frameworks (ZIFs), belonging to a sub-class of metal-organic frameworks (MOFs) have piqued the interest of researchers as prospective photocatalyst candidates. With huge specific surface area, tuneable porosity, diverse structure, ease of designing and controllable properties, ZIFs are highly sought-after material for pollutant degradation and clean energy generation. Additionally, ZIFs may undergo thermal processing to produce functional substances with similar structural characteristics but improved light responsiveness and electron transfer abilities. Numerous functional materials and better photocatalysts can be prepared by thermal treatment of ZIFs, formation of composites, heterostructures with other semiconductors or electron mediators which may have similar structural characteristics but better light capture abilities, charge transfer capabilities and strong redox properties. This paper carefully summarizes and analyses the applications of ZIFs based photocatalysts for photocatalytic organic pollutant degradation, hydrogen generation and CO 2 conversion. A sincere attempt has been made to lay down mechanistic insights into synergism of the structural and electronic properties of ZIFs with other catalyst counterparts for superior photocatalytic performance with focus on band structure analysis, charge transfer mechanisms and performance. Finally, the achievements, novelties and bottlenecks have been discussed and future research directions have been proposed. [Display omitted] • ZIFs as photocatalytic materials-Special structure and properties. • Synthetic routes to ZIFs based composites and heterojunctions. • Applications for CO 2 reduction, H 2 evolution and water treatment. • Detailed discussion on synergism with semiconductors and mechanisms. • Challenges, opportunities and future prospects were fully debated. [ABSTRACT FROM AUTHOR]

In the present work, mixed-spinel ferrite anchored onto graphitic carbon nitride (GCN) was synthesized for mineralization of antibiotic pollutant from waste water. A Z-scheme g-C 3 N 4 /Ni 0.5 Zn 0.5 Fe 2 O 4 nano heterojunction was fabricated by three step procedure: pyrolysis, solution combustion and mechanical grinding followed by annealing. The prepared photocatlyst was tested for degradation of Doxycycline (DC) drug under the natural sun light. Results revealed that the prepared heterojunction has maximum degradation efficiency of 97.10% pollutant in 60 min experiment. The Z-scheme heterojunction between g-C 3 N 4 and Ni–Zn ferrite improves the photoinduced charges separation and protection of redox capability and therby increases the photo degradation efficiency. The scavenging experiments suggested that O 2 −● and h+ as main active species responsible for degradation of the antibiotic. In addition, the dopant variation can drive the shists in band gap and energy band positiong too which makes then excellent candidates for synthesizing tunable heterostructures with organic semiconductors. The work focusses on designing and developing of saimpler but efficient magnetic heterojunctions with superior redox capability for solar powered waste water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Overview of fundamentals of Nb 2 O 5 as photocatalyst-structure and properties. • Heterojunction photocatalysts -Z and S scheme- charge transfer routes. • Recent advances in Nb 2 O 5 based heterojunctions for photocatalytic applications. • Strategies for improving the photocatalytic performance Nb 2 O 5 based heterojunctions. Significant advancements in the field of photocatalysis in recent years have highlighted the heterojunctions based on Nb 2 O 5 as a focal point of research. This comprehensive review diligently analyses the progress in Nb 2 O 5 -based heterojunctions for their application in photocatalysis, focusing on synthesis, characteristics and their pivotal role in addressing crucial energy and environmental challenges. The review emphasizes the fundamental principles of photocatalysis in pollutant removal and H 2 generation, elucidating key processes such as light absorption, charge generation and surface reactions. The different types of heterojunctions, their basic principles and role in enhancing the charge separation and overall photocatlytic performance have been discussed. The recent advances in Nb 2 O 5 -based heterojunctions are extensively discussed for the photocatalytic applications such as pollutants removal and H 2 evolution. Furthermore, the review delves into strategies employed to enhance the photocatalytic activity of Nb 2 O 5 -based heterojunctions such as doping, oxygen vacancies modification, morphological engineering and atomic control, as well as loading with support materials. Each strategy is explained, emphasizing its impact on charge separation and overall efficiency. The review concludes by highlighting existing challenges and providing insights into potential future directions that integrates synthetic processes, novel methods for photoelectric characterization, and an in-depth understanding of the local structure of Nb 2 O 5. This review serves as a valuable resource for researchers in the field, offering a comprehensive overview of the state-of-the-art in Nb 2 O 5 -based heterojunctions for advanced photocatalytic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen vacancies fundamentals and importance in photocatalysis. • Oxygen vacancies rich heterojunction-Synthetic strategies. • OVs rich Z-scheme and S-scheme heterojunctions- Photocatalytic mechanism. • Applications for Hydrogen production and water treatment. • The existing challenges and future perspectives. Photocatalytic removal of pollutants and energy production is a green, low cost and environment friendly technology for addressing the mounting pressure of energy crisis and environmental deterioration. Developing efficient photocatalysts is still a big challenge for accelerating the photocatalytic hydrogen production and pollutant degradation especially utilizing solar light. Therefore, constructing oxygen vacancies rich Z-scheme and S-scheme semiconductor heterojunctions emerged as a promising approach to enhance the light harvesting and increasing the redox capability of photocatalysts. This review comprehensively summarises the state of art focus on oxygen vacancy's role in photocatalysts especially in Z-scheme and S-scheme heterojunctions including synthesis process and modifications. In particular, the functions of oxygen vacancy in supporting the main processes in photocatalytic energy production and pollutant removal, such as light absorption, charge separation and conversion are highlighted in this review. The current issues and future prospective in oxygen vacancies rich heterojunctions for efficient photocatalytic removal of pollutant and energy production are also addressed. Finally, a brief discussion on challenges and future prospects is demonstrated. [ABSTRACT FROM AUTHOR]

The voluminous anthropogenic activities and non-regulated discharge of emerging pharmaceutical pollutants have led to deterioration of water quality characteristics and shortage of potable water. One of most ubiquitous problems is that the pharmaceutical pollutants are slowly developing resistance in pathogens, which increases the risks manifold. Conventional water treatment methods and technologies have been known to be inadequate for elimination of recalcitrant and emerging pollutants. Advanced oxidation processes have been exploited to the most for mineralizing the pollutants with some limitations especially toxic metal based catalysts and secondary pollution. However Fenton-based systems are considered to be safer as they utilize non-toxic chemicals. Homogeneous Fenton processes suffer from limitations as limited pH operational range, generation of Fe containing sludge etc. have shifted focus to heterogeneous systems. This review focusses on removal of pharmaceutical pollutants by homogeneous and heterogeneous Fenton, electro-Fenton, sono-Fenton, photo-Fenton and photo-electro-Fenton processes using nano-catalysts. Various types of new pharmaceutical pollutants, their emergence, characteristics and toxicity have been discussed to have an insight into quantity and variety. New Fenton-like catalysts have been designed and used for degradation of pollutants and high mineralization is also achieved in a wide pH-range. In addition Fenton catalysts capable of showing high mineralization using solar light have been prepared by various methods with and without iron based materials. In addition in this review we have also focused on complexities related to removal of pharmaceutical effluents and how they are addressed by Fenton systems. The review aims to assist researchers and engineers to gain fundamental understandings and critical view of Fenton process and its optimization processes, and hopefully with the knowledge it could bring new opportunities for the optimization and future development of Fenton process. The key advances in Fenton catalysts are innovations in design of ligands, junction designing for effective radical generation, reaction engineering, hydro-dynamical effects and complete mineralization. The combinations and coupling of biological oxidation, semiconductor photocatalysis with Fenton process for high performance pharmaceutical pollutants removal in pilot-scale experiments have been discussed and evaluated. • Pharmaceutical pollutants as emerging class of toxic pollutants. • Fenton, electro-Fenton, photo-Fenton processes: Safe, Cheap and environmental benign. • Controllable parameters for effective degradation of pharmaceutical pollutants. • Heterogeneous photo-Fenton reaction better than homogenous. • Focus on coupled Fenton and biological oxidation systems. [ABSTRACT FROM AUTHOR]