Graphitic carbon nitride (g-C3N4) has garnered considerable attention due to its exceptional characteristics, such as strong chemical and thermal stability and a tunable optical band gap, making it an ideal candidate for environmental remediation applications. Recent advancements focus on innovative modifications to enhance g-C3N4’s photocatalytic and adsorptive properties. Techniques like doping and composite synthesis have been employed to improve charge separation and light absorption, significantly increasing its photocatalytic efficiency. Additionally, g-C3N4’s notable electrochemical and photoelectrochemical properties contribute to its effectiveness in water splitting and pollutant degradation. A particularly novel aspect of this study is the integration of machine learning approaches and computational methods for structural and mechanistic studies of g-C3N4. These techniques are used to predict performance, optimize enhancements, and gain deeper insights into the material’s behavior, driving rapid progress in the field. This review explores g-C3N4’s crystalline structure, photocatalytic properties, and adsorption mechanisms, while also emphasizing the material’s potential for eco-friendly water treatment systems and the transformative role of advanced computational approaches in its development.

Biodiesel is considered eco-friendly, biodegradable, non-toxic, and carbon-neutral fuel. It is made from edible or non-edible oil feedstocks including other triglyceride sources. The production of biodiesel depends on the availability of a particular feedstock and the cost of desired raw materials. Biodiesel is mainly produced by the transesterification process using a suitable catalyst preferably a heterogeneous catalyst as it is more beneficial in terms of reusability, recovery, product purity, and production cost as well. Various reactors are developed to produce cost-effective biodiesel at the commercial level. The latest trend in biodiesel synthesis is the application of the machine learning (ML) technique to optimize the process parameters. The application of a mixture of two or more oils as feedstock either non-edible or edible oil is emphasized for biodiesel synthesis and is presently getting more importance. In this paper, the production of biodiesel from various mixed oil (hybrid oil) is reviewed and the effects of mixed oil on the reaction, physicochemical properties, fatty acid composition, and fuel quality of the product are discussed. The study highlighted the activity of various catalysts in the reaction of mixed oil and the economic feasibility. It was found that the ratio of mixed oil is an important factor in terms of conversion and quality of biodiesel. It is also revealed that the application of the ML technique is essentially useful to optimize production efficiency. The utilization of mixed oils will overcome the issues related to the non-availability of feedstocks and reduce the overall cost with improved quality of biodiesel. This approach enhances the production possibility of biodiesel at a large-scale and may boost the biorefinery sector satisfying the future energy demand if the research at the advanced level goes in the right direction.

Biodiesel has emerged as a versatile alternative to fossil-derived fuels which is a renewable and eco-friendly. The reactions via which biodiesel is synthesized from oil feedstocks are transesterification and esterification. These reactions are facilitated by certain catalysts which include both homogeneous and heterogeneous. Applications of homogeneous catalysts have been declining owing to certain limitations. The heterogeneous catalysts have been propounded as highly efficient catalysts for biodiesel production. However, the heterogeneous catalysts are also associated with a deficiency of active sites which adversely affect the catalytic performance. Recently, scientists have investigated various catalyst supports to enhance the catalytic activity among which metal organic frameworks (MOFs) and polyporous materials have gained the most attention. Several attractive features of MOFs such as high surface area, large porosity, tunable structures and functional groups, adjustable properties, uniformity in pore size, etc. are driving these materials as suitable catalysts for biodiesel synthesis. This review is focused mainly on the applications of MOFs-based catalysts and their catalytic performances in biodiesel synthesis. Different types of MOF catalysts, synthesis process, mechanisms, stability of the catalyst, and biodiesel properties are discussed herein. Moreover, other significant features of the synthesis of biodiesel such as production cost, economic viability, life cycle assessment, and applications of the machine learning techniques and reactors are highlighted and future perspectives are also discussed in this review. It can be emphasized from the study that MOFs could be developed as per the requirement for conversion of diverse qualities of feedstocks to biodiesel. Reactors such as microwave and ultrasound-assisted systems for the synthesis of both MOF catalyst and biodiesel are increasingly used in recent research to make the process cost-effective. Besides, applications of machine learning techniques in biodiesel research are found to be superior to conventional systems in modeling and optimization of the process.

Biodiesel is a renewable alternative biofuel to conventional fossil fuel. Biodiesel can be produced through esterification and transesterification reactions mainly catalyzed by acid, alkali, and enzyme catalysts. Among all of these catalysts, enzyme catalysts are more advantageous than chemical catalysts (alkali and acid catalysts) due to their high selectivity, mild reaction conditions, lower energy consumption, and yielding of good quality of products with no side reactions. However, because of the high costs of enzymes, there is a limit on the use of enzymatic operation on an industrial scale. The cost of enzymes can be reduced by improving the lifespan of catalysts. Over the last few decades, significant developments in enzyme-based biodiesel synthesis have been attained both on the laboratory and industrial scale, and production costs are also reduced. This review gives an overview of immobilized lipase-catalyzed and lipase-inorganic hybrid nanoflowers catalyzed biodiesel pro-duction, including the economic viability of enzyme catalysts and idea about different reactors which is used for enzymatic transesterification reaction.