The depolymerization of lignin over polyoxometalate catalysis: A review

Lignin, as the most abundant natural aromatic compound, holds immense potential for the production of fuels and fine chemicals, making it a focal point in green chemistry. The efficient depolymerization of lignin hinges on the discovery of catalysts that are not only efficient but also stable and recyclable. Understanding the structure-function relationships and mechanisms governing lignin-catalyst depolymerization is paramount for its effective valorization. Polyoxometalates (POMs) have emerged as promising candidates due to their versatile structural composition and design flexibility. In this review, we explore the utilization of POMs in various methods of lignin transformation, encompassing oxidative catalysis, reduction catalysis, and photocatalysis. By summarizing these approaches, we aim to elucidate the current trends and challenges in the depolymerization of lignin using POMs.