Mesoporous graphitic carbon nitride supported CoPd alloy nanoparticles as catalysts for various reactions of terpenes

Heterogeneous catalysis has attracted intensive attention due to the prevailing properties of heterogeneous catalysts such as high reusability and chemical stability. In recent years, 2D materials have found them enormous usage in heterogeneous catalysis owing to their unique optical, thermal, and electrical properties. Among them, mesoporous graphitic carbon nitride (mpg-CN) which is a polymeric, metal-free, non-toxic and low-cost material, has received great attention in the (photo)catalysis field. However, it suffers from several drawbacks such as fast charge carrier recombination and large band gap cause to construct heterojunction between another semiconductor or metal nanoparticles (NPs). Besides, the designing of platinum-group metals (PGM) based NPs have been dominating the heterogeneous catalysis field owing to their high catalytic activity, stability, and tolerance against poisoning. Among them, palladium (Pd) has gained the highest interest owing to its broader abundance and Pt-liked catalytic activity. Moreover, Pd demonstrates high activity in many organic reactions e.g. hydrogenation, dehydrogenation, oxidation, coupling reactions, etc. However, due to the current inflation in precious metals, Pd is the third most expensive PGM metals today, which limits its practical usage in industry. Hence, the last decade has witnessed the development of various bimetallic Pd alloys since they are more economical, and they boost catalytic activity compared to monometallic cunterparts owing to the synergistic effects between two divergent metals. However, a facile yet efficient synthesis of bimetallic PdM alloys, where M is the first-row transition metal, possesing high catalytic activity and stability is highly required to enhance their industrial usage. In this thesis, we developed a facile synthesis protocol for the synthesis of designed novel heterogeneous catalysts composed of mpg-CN serving both as support and stabilizer and bimetallic alloy NPs and tested their catalytic activity in various reactions of terpenes including dehydrogenation, hydrogenation, and oxidation. For this purpose, mpg-CN was prepared by using a hard-template polycondensation method and exfoliated in solvent to anchor CoPd alloy nanoparticles between its nanosheets. In the presented protocol, mpg-CN served both as stabilizer and support material for yielded NPs. CoPd alloy NPs were obtained via the colloidal synthesis method in different compositions. The as-synthesized CoPd/mpg-CN nanocatalysts were characterized by using advanced techniques. The proposed synthetic method allowed to synthesize of nearly monodisperse CoPd alloy NPs with an average particle size of 3.0 ± 0.4 nm. After the construction of the prepared bimetallic alloys on the support material and a detailed investigation of their structural and photophysical properties, as-synthesized CoPd/mpg-CN nanocatalysts were utilized in dehydrogenation, hydrogenation, and oxidation of natural terpenes. Among all prepared CoPd/mpg-CN nanocatalysts, Co37Pd63/mpg-CN served the highest activity for all reactions. The dehydrogenation of 5 substrates was achieved in high conversion yields (≥91%). Also, the hydrogenation and oxidation products of several terpenes were obtained, successfully. The reusability tests for dehydrogenation, hydrogenation, and oxidation showed that Co37Pd63/mpg-CN nanocatalysts can be reutilized up to 5 cycles without significant loss of its activity.