Green synthesis of SiO<sub>2</sub> from <i>Equisetnm arvense</i> plant for synthesis of SiO<sub>2</sub>/ZIF-8 MOF nanocomposite as photocatalyst
Babak Azari, Afshin Pourahmad, Babak Sadeghi, Masoud Mokhtary
Abstract
Equisetnm arvense plant extract was used for preparing amorphous SiO2. For preparing of SiO2/zeolitic imidazolate framework-8 (ZIF-8) nanocomposite by solvothermal method, the synthesized SiO2 was added to synthesis mixture ZIF-8. The photocatalytic activity of SiO2/ZIF-8 was investigated systematically by degrading crystal violet as a cationic dye under UV light irradiation. The photodegradation of crystal violet by SiO2, ZIF-8 and SiO2/ZIF-8 samples was 13.7%, 25.6% and 75.6% during UV-light irradiation for 15 min. Among synthesized samples (SiO2, ZIF-8 and SiO2/ZIF-8), the SiO2/ZIF-8 exhibited highest photocatalytic activity and improved stability compared to pure SiO2 and ZIF-8. As evidenced from SEM and TEM images, ZIF-8 particles without aggregation located over SiO2. The enhancement of the photocatalytic activity is due to the fact that the introduction of insulator SiO2 in SiO2/ZIF-8 composites can modify the surface state of the composite; more importantly, the energy level of SiO2 can help accelerate the separation and transfer of electron-hole pairs of ZIF-8. The SiO2/ZIF-8 photocatalyst did not show any obvious loss of photocatalytic activity during five cycles, which indicate that the heterostructured photocatalyst was stable and can be used repeatedly.