Dear Colleagues,

Catalysis is one of the fundamental pillars of green chemistry. The design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances has led to the development of catalysts and catalytic systems to achieve the dual goals of environmental protection and economic benefit. The purpose of the issue is to find out more about the application of nanotechnology toward environmental remediation and organic synthesis, and the outcomes of this study are very essential to society. The nanomaterials rummage-sale in organic transformation/synthesis reactions are mainly used as solid acid catalysts by the replacement of liquid acids. Acids such as HF, H₂SO₄, HClO₄ and H₃PO₄ have been widely used in organic transformations and in oil refining, petrochemical and chemical industries. Since 1940, the tendency has been to replace these liquid acids with other solid acids which have several advantages compared to liquid acids. Solid acid catalysts have the following advantages for their use in industry: i) easy handling, ii) catalyst regeneration iii) simplicity and versatility of process engineering, iv) decreased reactor and plant corrosion problem, v) environmentally safe disposal.

One of the most important factors for the evaluation of treatment efficiency is the ability to reduce concentrations of chemical substances in wastewater. Physical, chemical and biological methods are well known for the treatment of wastewater. The disadvantage of precipitation methods is the sludge formation. Chemical coagulation and flocculation use a large amount of chemicals and the generated sludge may contain hazardous materials. Advanced oxidation processes (AOPs) such as semiconductor photocatalysis, UV/H₂O₂, Fenton, photo-Fenton, ozonation and O₃/H₂O₂ processes are used for the treatment of recalcitrant compounds in water and wastewater. These processes involve highly reactive intermediates particularly the hydroxyl radical (•OH). Hydroxyl radical is a powerful oxidizing agent with an oxidation potential of 2.8 eV.

Current research is mainly focused on the replacement of environmentally hazardous processes with energy-efficient routes to avoid the use and production of harmful products. Semiconductor oxides as catalysts offer an alternative green route for organic transformations. Nanosized semiconductor oxides attracted great attention mainly because of their wide applications in pollutant mineralization and organic synthesis. The catalytic efficiency of these semiconductor oxides can be enhanced by doping with metals/ non-metals/anions/metal halides.

The studies invited to this Special Issue should have a focus on the recent development of nanomaterials especially solar active photocatalysts for wastewater treatment, selective organic transformation and energy-related applications. Although there is a lot of academic knowledge and expertise in this area across a multitude of disciplines, many of the materials being inactive, expensive and lacking reusability. This issue will supplement the knowledge that relates to materials synthesis, characterization and their effective utilization related to the environment which is directly helpful to society.

The Special Issue is also helpful for interdisciplinary collaboration.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

• Modification of metal oxides /sulphides and their multiple applications such as water splitting, Pollutant degradation, H₂ productions and CO₂ reductions
• Development of solar active photocatalysts for environmental remediation and organic synthesis
• Semiconductor mediated synthesis of novel heterocyclic compounds for biological applications
• Investigation of organic photochemical reaction and mechanisms
• Catalysis based synthesis.
• Materials science
• Nanoscience and technologies

We look forward to receiving your contributions.

Dr. Balu Krishnakumar
Dr. Mani Durai
Dr. Sakthivel Kumaravel
Guest Editors

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• TiO₂
• ZnO
• metal sulfides
• solar active catalyst
• degradation, dye removal
• water splitting
• H₂ production
• solid acid catalyst
• organic transformation