Recent progress in polymer nanosheets for photocatalysis

Polymers have been considered as promising photocatalysts for energy conversion and environmental remediation, because of their inherent advantages such as adjustable optical and electronic properties as well as abundant active sites. However, it is difficult for polymers without effective design to achieve ideal photocatalytic performance. Compared with bulk polymers, polymer nanosheets obtained by exfoliation have the thickness of single or multiple atomic layers, which possess numerous unique advantages, such as more accessible active sites, shorter carrier transport distances, a prolonged lifetime of photogenerated carriers and the atomic level regulation of the backbone. Therefore extensive efforts have been focused on photocatalysts based on polymer nanosheets, and remarkable progress has been reported. In this review, the principles of photocatalytic water splitting, pollutant degradation and CO2 reduction are briefly introduced. And then recent advances in polymer nanosheets (conjugated microporous polymers, covalent organic frameworks, conjugated triazine frameworks and carbon nitrides) and their heterojunctions in the above-mentioned fields are highlighted. Specifically, the effects of the modification strategy on their light absorption ability, carrier migration, and photocatalytic activity are discussed. Finally, the important challenges and potential opportunities for developing polymer nanosheets and their heterojunctions as high-performance photocatalysts are envisaged. The insights exhibited in this review can provide a useful guidance for the design and development of polymer nanosheet based photocatalysts. Polymer nanosheets (CMPs, COFs, CTFs and carbon nitrides) have many unique advantages. This review summarizes the recent advances in polymer nanosheets for efficient photocatalysis including water splitting, pollutant degradation and CO2 reduction.