ZIF-8/TiO2 Composite Mesocrystals: Preparation and Photocatalytic Activity

Microstructure, particle size and specific surface area of TiO2 are crucial factors influencing its photocatalytic activity. Mesocrystals represent a type of superstructural material formed by inorganic nanoparticles aligned along a common crystallographic axis, holding significant research potential in the field of photocatalysis. This study employed ammonium hexafluorotitanate and boric acid as titanium precursor and fluorine ion scavenger, respectively, and used a blend of anhydrous ethanol and deionized water as reaction medium. NH4TiOF3 mesocrystals precursors were prepared by a facile green method. Subsequently, washing with boric acid solution enabled the transformation of NH4TiOF3 mesocrystals into TiO2 mesocrysals through topotaxial conversion. Ultimately, the TiO2 mesocrystals were functionalized with ZIF-8 nanoparticles, and the photocatalytic degradation activity of the obtained ZIF-8/TiO2 composite mesocrystals was studied. The experimental results shows that ZIF-8 nanoparticles can uniformly nucleate on the surface of TiO2 mesocrystals, resulting in a relatively dense coating layer. ZIF-8/TiO2 composite photocatalyst exhibits a higher specific surface area and a narrower band gap. Meanwhile, the separation efficiency of photogenerated electrons and holes is also improved to a certain extent. Notably, the sample M-TiZIF-2 (with addition of 4 mmol Zn(NO3)(2)) demonstrated superior photocatalytic activity, and achieved a first-order reaction rate of 42-fold that of TiO2 mesocrystals and 16-fold that of pristine ZIF-8 nanoparticles. In conclusion, the synergistic effect of ZIF-8 nanoparticles and TiO(2 )mesocrystals significantly augments the photocatalytic performance of the ZIF-8/TiO2 composite mesocrystal materials.