Improved photocatalytic activity of TiO 2 with a regulated covalent organic framework thin film.

In this work, one-dimensional TiO 2 nanotube arrays are coupled with a covalent organic framework (COF) thin film with a controlled thickness to form a three-dimensional heterojunction, which exhibits a 3.3-fold higher hydrogen evolution rate than that of TiO 2 , and becomes active for CO 2 conversion, compared to the bare COF. Such high activity results from the large difference in Fermi levels forming an internal electric field at the interface.