Cerium-based metal-organic framework-modified natural mineral vermiculite for photocatalytic nitrogen fixation under visible-light irradiation

In order to protect the environment and economize energy, a nitrogen-fixing photocatalyst, VMCeact, is investigated in this work. This catalyst is prepared from a natural mineral, vermiculite, and modified by Ce-based metal-organic framework, Ce-UiO-66. Vermiculite was treated with formic acid; thus, Ce-UiO-66 particles grew in-situ on vermiculite; then, Ce-UiO-66 particles were activated by ultraviolet irradiation. The vermiculite absorbed visible light with a narrow band gap, and transferred photogenerated electrons to the active sites on Ce-UiO-66. Moreover, the lamella structure of vermiculite protected Ce-UiO-66 during photocatalytic process. Therefore, with only 45.92 wt% of Ce-UiO-66, the nitrogen fixation performance of VMCeact was 2.29 times that of pure activated Ce-UiO-66 particles under 455 nm light irradiation (apparent quantum efficiency of 4.49%), and retained at least 96.05% performance after 7 × 24 h of photocatalytic reaction. This cost-reduced, efficient and stable photocatalyst has the opportunity to facilitate environmentally friendly ammonia production.