Ceria-Based Materials for Thermocatalytic and Photocatalytic Organic Synthesis

Abstract

Value-added chemicals, fuels, and pharmaceuticals synthesized by organic transformation from raw materials via catalytic techniques have attracted enormous attention in the past few decades. Heterogeneous catalysts with high stability, long cycling life, good environmental-friendliness, and economic efficiency are greatly desired to accomplish the catalytic organic transformations. With the advantages of reversible Ce3+/Ce4+ redox pairs, tailorable oxygen vacancies, and surface acid–base properties, ceria-based catalysts have been actively investigated in the fields of catalytic organic synthesis. In this Review, we summarize the fundamentals and latest applications of ceria-based heterogeneous catalysts for organic transformations via thermocatalytic and photocatalytic routes. The fabricating approaches of various ceria and ceria-based catalysts and their structure/composition–activity relationship are discussed and prospected. The advanced characterization techniques and theoretical methods for reaction mechanism studies over CeO2-based catalysts are summarized and discussed. This comprehensive Review provides a basic understanding of the structure–performance relationships of ceria-based catalysts for organic synthesis. In addition, it also provides some insights and outlooks in the design and research direction in the ceria-based catalysts with better performance.

Visible-Light-Induced Selective Oxidation of Amines into Imines over UiO-66-NH2@Au@COF Core–Shell Photocatalysts

“…Imines as valuable intermediates are comprehensively applied in the fields of medicine and biology, in which the aerobic oxidative coupling of amines to generate corresponding imines has become a research hotspot. Compared with conventional thermocatalysis, photocatalysis as an environmentally friendly and cost-effective method has attracted widespread attention for chemical synthesis at room temperature. − Up to now, a series of traditional semiconductors such as TiO 2 , CdS, and C 3 N 4 have been extensively explored for the visible-light-driven selective oxidation of amines to imines; − however, their poor structure adjustment and low photocatalytic efficiency have limited their further applications in photocatalysis. Recently, emerging metal–organic frameworks (MOFs) with large surface areas and adjustable pores have attracted increasing attention as promising photocatalysts for organic synthesis because the metal-containing clusters in MOFs can act as semiconductor dots and the organic linkers as photoinduced electron initiators to complete the electron transfer via the linker to the metal cluster charge-transfer (LCCT) route. − However, some intrinsic defects of MOFs, like poor visible-light adsorption and low stability as well as deficient efficiency of light utilization, have greatly restricted their practical applications.…”

Support–Activity Relationship in Heterogeneous Catalysis for Biomass Valorization and Fine-Chemicals Production

“…With the advantages of reversible Ce 3+ /Ce 4+ redox pairs, tailorable oxygen vacancies, and surface acid−base properties, ceria-based catalysts are actively investigated in the fields of catalytic organic synthesis [135]. This is the reason why, in recent years, several reviews on special organic reactions over CeO 2 -based catalysts were reported, such as transformations of nitriles and amides [136], CO 2 conversion with alcohols or amines [137,138]; sustainable oxidation processes [139] and transformations of biomass, its derivatives, and downstream chemicals [140].…”

Photocatalytic Conversion of Plastic Waste: From Photodegradation to Photosynthesis

“…In recent years, upcycling catalytic methods for plastics conversion, such as thermocatalytic and photocatalytic routes, have received increasing attention because the plastic waste can be upgraded into valuable fuels, chemicals, or materials with additional economic benefits. [30][31][32][33][34][35][36] Compared to the thermochemical route, including pyrolysis and gasification, which generally require large energy inputs and harsh reaction conditions such as high temperature and pressure, photocatalysis is considered as a greener and cheaper technique owing to its mild conditions of ambient pressure and temperature using sunlight or artificial light (e.g., LEDs with low-energy consumption) as the energy source. [37][38][39][40][41][42] Furthermore, in contrast with the severe conditions applied during thermocatalysis, the mild process of photocatalysis has great potential for the precise activation of specific chemical bonds with other functional groups preserved, which can achieve high selectivity toward targeted products.…”