Hollow Covalent Triazine Frameworks with Variable Shell Thickness and Morphology

Covalent triazine frameworks (CTFs) are a class of semiconductive porous materials, showing enormous potential in many applications, such as gas adsorption and storage, and heterogeneous catalysis. At present, most of the studies on CTFs are focused on the structural design, synthesis, and applications, whereas very little attention is paid to morphological study, probably due to the difficulty in the control of the morphology via the conventional synthetic methods. In this work, a general approach is reported to fabricate morphological controllable CTFs by virtue of a mild polycondensation reaction via template method. As a proof of concept, a new type of hollow-structured CTFs is developed for the first time. The shell thickness of the hollow CTFs can be conveniently tuned by varying the amount of the template. Notably, the morphologies can be transformed from sphere to bowl with the decrease of the shell thicknesses. The hollow morphology of CTFs can efficiently improve the photocatalytic hydrogen evolution performance, in which the hydrogen evolution rate can be boosted by about 4 times as compared to the bulk state. The present study not only shows an effective strategy to construct morphology controllable CTFs, but also demonstrates an effective way to enhance photocatalytic performance for CTFs.