A novel (Ti/Ce)UiO-X MOFs@TiO2 heterojunction for enhanced photocatalytic performance: Boosting via Ce4+/Ce3+ and Ti4+/Ti3+ redox mediators

Titanium-substituted cerium-oxo-based UiO MOFs with terephthalate linkers modified by various groups (–Br, –NH2, –NO2) or their derivatives (N-heterocyclic or biphenyl groups) were combined with titanium dioxide in a multistep route to obtain a core-shell-like architecture. DFT simulations showed that Ce- and bimetallic Ti/Ce-MOFs exhibited different charge compensation. Extended characterization revealed the formation of heterojunctions between the (Ti/Ce)UiO-X MOFs and TiO2 nanoflowers, suitable band edge positions, and high specific surface area and porosity, which resulted in effective electron transfer and excellent photocatalytic activity. The photoactivity of the (Ti/Ce)UiO-X@TiO2 composites for hydrogen production or phenol degradation varied according to the order –NH2 > biphenyl > –N– > –H > –Br > –NO2 > pristine TiO2 or –Br > –NH2 > –NO2 > –N– > –H > biphenyl > pristine TiO2. The photocatalytic hydrogen production rate of (Ti/Ce)UiO-66-NH2@TiO2 was 4724 and 19.3 μmol·gcat–1 after 4 h of UV–Vis and visible light irradiation, which were 79 and 19 times higher than that of pristine rutile, respectively.