Liu Cheng, Chen Qi, Chen Yueling, Yu Jimmy C, Wu Jionghua, Wu Ling
State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou 350116, China.
Department of Chemistry, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong 999077, China.
J Colloid Interface Sci. 2025 Jan 15;678(Pt A):616-626. doi: 10.1016/j.jcis.2024.08.218. Epub 2024 Aug 30.
Photocatalysis, which uses sunlight, N and HO to produce NH, is a more sustainable approach to N fixation than the Haber-Bosch process. However, its efficiency is severely limited by the difficulty of activating NN bonds. This work presents metal (M = Cu, Fe, V)-substituted MIL-125(Ti) (MIL-(MTi)) for photocatalytic N fixation without using any sacrificial agents. Structural characterizations reveal that the active sites including oxygen vacancies (OV) and Ti species are formed by the resulting crystal distortion due to the partial substitution of Ti by other metal ions (Cu, Fe, V) in MIL-125(Ti). MIL-(CuTi) possesses a larger number of OV and Ti compared to MIL-(FeTi) and MIL-(VTi) due to the larger valence difference between Cu and Ti. These active sites not only promote the adsorption and activation of N and HO, but also facilitate the photogenerated charge mobility. Photogenerated holes oxidize HO to produce O and H. Photogenerated electrons reduce N activated on Ti sites by combining with H to form NH. Therefore, MIL-(CuTi) shows the highest NH production rate 46.5 µmol·h·g, which is much higher than that (1.2 µmol·h·g) of the pristine MIL-125(Ti). This work provides a new insight into rational design for artificial N fixation systems by the construction of the active site.
光催化利用阳光、氮气和水来产生氨，与哈伯-博施法相比，是一种更具可持续性的固氮方法。然而，其效率受到激活氮氮键困难的严重限制。这项工作展示了金属（M = 铜、铁、钒）取代的MIL-125（钛）（MIL-(MTi)）用于光催化固氮，且无需使用任何牺牲剂。结构表征表明，由于在MIL-125（钛）中钛被其他金属离子（铜、铁、钒）部分取代，导致晶体畸变，从而形成了包括氧空位（OV）和钛物种在内的活性位点。由于铜和钛之间较大的价态差异，与MIL-(FeTi)和MIL-(VTi)相比，MIL-(CuTi)拥有更多的氧空位和钛。这些活性位点不仅促进了氮气和水的吸附与活化，还促进了光生电荷迁移。光生空穴将水氧化生成氧气和氢离子。光生电子通过与氢离子结合，还原在钛位点上活化的氮气，形成氨。因此，MIL-(CuTi)表现出最高的氨生成速率46.5 μmol·h⁻¹·g⁻¹，远高于原始MIL-125（钛）的生成速率（1.2 μmol·h⁻¹·g⁻¹）。这项工作通过构建活性位点，为人工固氮系统的合理设计提供了新的见解。
