Both pristine metal-organic frameworks (MOFs) and graphitic carbon nitride (g-C3N4) displayed outstanding photocatalytic performances toward H2 production, CO2 reduction, Cr(VI) reduction and organic pollutants degradation. To further enhance their photocatalytic performances under visible light or sunlight irradiation, MOFs and g-C3N4 were combined to construct g-C3N4/MOF heterojunctions with the purpose of overcoming their individual disadvantages like fast recombination of pohotogenerated electron-hole pairs. The fabrication methods, characterizations, photocatalytic performances and the corresponding mechanism of some typical g-C3N4/MOF composites were highlighted. Also, the prospective and challenges of this research field were declared.

Powerful combination of MOFs and C3N4 for enhanced photocatalytic performance

The photocatalytic hydrogen evolution on inorganic semiconductors has been studied for several decades. However, the conversion efficiency of solar energy is still poor caused by the recombination of photo-generated electron-hole pairs. Semiconductors - metal organic frameworks (MOFs) hybrid photocatalysts are being regarded as promising candidates due to large surface area and porosity. Here we reported the coordinative integration of a composite material with efficient capacity of H2 evolution driven by solar light, namely TiO2@ZIF-8, made up of titanium dioxide hollow nanospheres (TiO2 HNPs) externally decorated with zeolitic imidazolate framework-8 (ZIF-8) via a facile sonochemical route. The resulting composite demonstrates the high dispersion of ZIF-8 on the surface of TiO2 HNPs and this kind of close connection makes for an efficient photocatalyst through the synergistic effect. Up to 50.89% of apparent quantum efficiency (AQE), the hybrid double-shell HNPs exhibits 3.5 times higher H2 evolution rate (HER) than the bare TiO2 HNPs under solar light and shows good stability and recyclability. It is further proposed by photoluminescence spectra and optoelectronic measurement that the remarkably enhanced photocatalytic activity of TiO2@ZIF-8 is not only attributed to the efficient charge separation with electron injection from ZIF-8 to TiO2 HNPs, but also more active reaction sites provided by cavity structure of ZIF-8. Overall, this work exemplifies that surface engineering of semiconductors with MOFs is a great strategy to achieve advanced photocatalytic performance for solar energy conversion.

Self-template synthesis of double-shell TiO2@ZIF-8 hollow nanospheres via sonocrystallization with enhanced photocatalytic activities in hydrogen generation

ZIF-8-modified MnFe2O4 with high crystallinity and superior photo-Fenton catalytic activity by Zn-O-Fe structure for TC degradation

Rapid synthesis of Ag/AgCl@ZIF-8 as a highly efficient photocatalyst for degradation of acetaminophen under visible light

Probing the photo- and electro-catalytic degradation mechanism of methylene blue dye over ZIF-derived ZnO.

Controllable conjunction of semiconductors with metal organic frameworks (MOFs) has been an efficient tool to enhance the chemical and physical properties of semiconductors by forming semiconductor–MOF hybrid structures. Herein, a novel MOFs-derived strategy to fabricate ZnO/ZIF-8 hybrid photocatalysts via the micro-catalysis technique by using ZIF-8 as a precursor and AgNO3 as a catalyst is reported. The properties and structures of ZnO/ZIF-8 hybrid photocatalysts can be effectively controlled by adjusting the concentration of AgNO3 solution. The as-prepared ZnO/ZIF-8 hybrid photocatalysts were characterized by XRD, SEM, TEM, UV-vis, BET and other techniques. Their photocatalytic performances were evaluated by degradation of rhodamine B (RhB) solution under UV light. The results indicate that ZnO/ZIF-8 photocatalysts exhibit excellent photocatalytic properties. ZnO/ZIF-8(50) exhibits the highest photocatalytic activity and can degrade 98.17% RhB after 12 min of UV light irradiation, which is higher than the degradation ability of P25 (95.05%), benefiting from the synergistic effect of ZnO and ZIF-8. Furthermore, the ZnO/ZIF-8 (50) photocatalyst shows high photostability. After four repeated cycles, its photocatalytic efficiency could be maintained at 95.54%.

Ziling Wu

Papers

Synthesis of ZnO/ZIF-8 hybrid photocatalysts derived from ZIF-8 with enhanced photocatalytic activity