Temperature-Dependent Synthesis of Oxygen Vacancy-Rich NH₂–UiO-66: A Strategy for Sustainable Photocatalytic Nitrogen Fixation

Photocatalytic nitrogen fixation is a promising strategy for sustainable energy production, with efficient and cost-effective photocatalysts being crucial for its success. In this study, oxygen vacancy-rich photocatalysts (100-U, 200-U, and 300-U) were successfully synthesized via low-temperature calcination of NH2–UiO-66. Electron paramagnetic resonance analysis confirmed a significant increase in oxygen vacancies during calcination, enhancing active sites for photogenerated charge carrier capture. The bond length, thermogravimetric analysis, and X-ray diffraction revealed that calcination at 200 °C, compared to other temperatures, led to the cleavage of C1–C2 bonds and the breakage of Zr–OH–Zr bonds, promoting oxygen vacancy formation while preserving structural integrity. Photocatalytic results showed that the 200-U sample exhibited the highest nitrogen fixation performance, with an NH3 yield of 17.2 μmol g–1 h–1, approximately twice that of the original NH2–UiO-66. This work provides valuable insights into the partial decomposition process and oxygen vacancy formation mechanism, contributing to the design of photocatalysts with abundant oxygen vacancies.