Heterogenization of homogeneous photocatalysts utilizing synthetic and natural support materials

Homogeneous photocatalysis has considerably contributed to green applications such as energy production and environmental decontamination. Currently, researchers mainly focus on the search for sustainable processes that can generate valuable chemical compounds with high selectivity and aid in the complete mineralization of hazardous compounds. Although homogeneous photocatalysts exhibit superior performance, their recovery after the reaction is difficult. The 3Rs process,i.e., recovery, recycling and reuse of photocatalysts respectively, is critical to make a photocatalytic process eco-friendly. Heterogenization of homogeneous photocatalysts is considered as an effective method to not only realize the recycling of homogeneous photocatalysts, but also enhance the overall photocatalytic activity. Conventional methods have employed synthetic materials for the heterogenization of homogeneous photocatalysts. Nevertheless, scientists have discovered that natural polymer sources can be alternatives due to their excellent chemical, mechanical, and electrical properties for applications under harsh reaction conditions. In this review, we have summarized state-of-the-art techniques employed for the heterogenization of homogeneous photocatalysts using various supporting materials in terms of design and preparation. First, we have organized these strategies into different categories, such as microporous encapsulation, dye-sensitized semiconductors, metal-organic framework (MOF) construction, carbon material fixation, synthetic polymer attachment and natural origin supports. To provide readers with deeper insights into this field, we have presented some fundamentals of homogeneous photocatalysis with respect to environmental applications and its heterogeneous strategies. Furthermore, we have discussed the performance of heterogeneous photocatalysts prepared from these methods, including photocatalytic performance, product selectivity and reusability. Finally, we have concluded with different aspects on the current challenges and new aspects in emerging technologies.