Controllable assembly of single/double-thin-shell g-C₃N₄ vesicles via a shape-selective solid-state templating method for efficient photocatalysis

Mimicking natural thylakoid vesicles is an effective approach for facilitating photoabsorption and charge separation over photocatalysts. However, bulk materials cannot function well with a short photocarrier transport distance while thin-layers suffer from preparation difficulty due to the ease of structural collapse. Herein, inspired by natural thylakoid vesicles, a solid-state thermolysis templating method using the shape selectivity of MCM-41 and melamine precursor has been developed to assemble stable thin-shell g-C₃N₄ vesicles and their heterojunctions. The relatively narrow channel of MCM-41 allows the oligomerization of melamine inside the pore but inhibits its further polymerization into melon. With increasing temperature, oligomers begin to form and migrate out of the channel and polymerize selectively on the open-up outer surface into the vesicle structure. Single- and double-thin-shell g-C₃N₄ vesicles as well as their heterojunctions have successfully been fabricated through templating by MCM-41, hollow MCM-41 and MO_x/MCM-41 (M = Ag, Fe, Co, Cu, and Ni) as evidenced by TEM. A uniform shell thickness can be precisely controlled from 17.5 to 42.1 nm. The tailored g-C₃N₄ vesicles exhibit enhanced photocatalytic activity and stability for the hydrogen evolution reaction which results from the enhanced photoabsorption and suppressed charge recombination. This new method is versatile for encapsulation of the secondary component including metals and metal oxides in g-C₃N₄.