A facile and scalable synthetic method for covalent organic nanosheets: ultrasonic polycondensation and photocatalytic degradation of organic pollutants

Covalent organic framework nanosheets (COF NSs or CONs), as compared to their bulk counterparts two-dimensional (2D) covalent organic frameworks (COFs), exhibit superior performance in many aspects due to their fully accessible active sites benefiting from their ultrathin porous 2D structures. The development of a scalable synthetic methodology for CONs is crucial to further exploration of their unique properties and practical applications. Herein, we report an efficient strategy to fabricate ultrathin CONs through direct polycondensation of monomers under ultrasonic treatment and mild conditions. This method is facile and scalable, which is demonstrated by gram-scale synthesis of two ultrathin 2D CONs in several hours. Moreover, the as-prepared ultrathin CONs show excellent heterogeneous photocatalytic performance for the degradation of organic pollutants (dyes as representatives), remarkably superior to the bulk COFs prepared from the corresponding monomers under solvothermal conditions. This research provides a new roadmap for the scalable and facile synthesis of ultrathin CONs, which is of paramount importance for fully exploring the tremendous potential of this emerging type of 2D material.