In Situ Growth of Highly Dispersed TiO2 in Covalent Organic Frameworks for Photocatalytic H2 Evolution.

Titanium dioxide (TiO2) has the disadvantages of being difficult to excite and easily agglomerating in use. The imine-linked covalent organic frameworks (COFs) have shown various excellent properties in diverse fields, but the drawbacks such as monofunctionality and poor light-corrosion resistance are the problems that need to be improved in photocatalytic applications. In this paper, the imine-linked COF (COF-Im) was prepared and then transformed into a quinoline-based COF (COF-Qui) by an aza-Diels-Alder reaction, which successfully improved the light absorption and stability of the COFs. The COF-Qui-TiO2 heterojunction photocatalyst was successfully prepared by in situ growth of TiO2 in pores of COF-Qui. The highest H2 evolution rate of COF-Qui-TiO2 was 5373 μmol·h-1·g-1, and it maintained good performance and a stable structure after 5 cycles. This work provided valuable experience for the development of novel, efficient heterojunction photocatalysts.