The growing awareness for environmental sustainability has been the thrust behind enormous developments in the area of chemistry. Sustainable or green chemistry is a type of enterprise that is implicated in the design of products as well as processes that minimize or do not generate and use hazardous materials. Green catalysis, on the other hand, forms a vital component of the green chemistry field and is an area employed in the design of active, non-toxic, and cost-effective catalysts. The present paper reports on new trends in the fields of sustainable chemistry and green catalysis. Emphasis is given to innovative approaches and technologies that decrease the environmental footprint of the chemical industry and enable it to proceed toward the present and future of sustainability.
Principles of Green Chemistry
Green chemistry is based on a set of 12 principles developed to guide chemists in their endeavor to develop processes and products that will be more sustainable. These principles dwell on waste prevention, using renewable feedstocks, energy efficiency, and reduction of toxicity. Following such courses enables chemists to plan processes that are environmental friendly and, at the same time, not only cost-effective but also safe for human health.
One of the key basic principles underpinning green chemistry is catalysis. A catalyst is a substance that increases the rate of a chemical reaction but is left unchanged in quantity and kind at the end of the reaction. Green catalysis is involved in the development of effective, non-toxic, and renewable catalysts ready to work in mild conditions. Such an approach reduces the environmental impact of chemical processes and raises their efficiency.
Advances in Green Catalysis
Subsequently, in the new horizons developed, there are now green and improved catalysis methods, among other novel catalysts. A good example is the polyoxometalates in catalysis. These have been a topic of great interest. Polyoxometalates are a class of metal-oxygen clusters that show unprecedented properties, rendering them useful in nearly all kinds of catalytic systems. They can fit into the oxidative processes of organic compounds, ester hydrolysis, and the degradation of biomass into value-added chemicals.
One of the interesting applications of POMs is in the area of nanocatalysis of nerve agent-simulant hydrolysis. Thus, scientists synthesized zirconium-containing POMs, which are good catalysts in the hydrolysis of these toxic compounds, so that the way to their environmentally friendly disposal is opened with an ecologically desired profile. These POMs show very good stability, are easily reusable a number of times without losing activity, and thus reveal the realistic perspectives of their use in practice in processes of decontamination.
Another important innovation in green catalysis is the use of ionic liquids as solvents and catalysts. ILs are salts that are liquid at room temperature and possess unique properties, including non-volatility, high thermal stability, and tunable solubility. In fact, these very properties make ILs most suitable for use in green catalysis, which could replace conventional organic solvents, which are usually very volatile and often highly toxic. In addition, ILs can be designed to have specific catalytic functions, which further increases their versatility.
The application of ILs in combination with POMs to form a hybrid catalyst system has also been reported. Based on the proton density of POM and the type of cations in the employed ILs, the resulting hybrid catalysts could be successfully shown to be applied in the conversion of renewable feedstocks, such as biomass, into valuable chemicals. For example, fructose can be efficiently catalyzed to 5-hydroxymethylfurfural (HMF), which is a key bio-based chemical intermediate, using IL-modified POMs. The whole process is useful both as far as renewable resources are concerned and also under mild conditions, and thus saves the overall burden that is put on the environment.