Li Xiaohong, Yang Lan, Liu Qilong, Bai Wei, Li Huiyi, Wang Mengxiang, Qian Qizhu, Yang Qinghua, Xiao Chong, Xie Yi
Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Institute of Energy, Hefei Comprehensive National Science Center, Hefei, Anhui, 230031, P. R. China.
Adv Mater. 2023 Nov;35(44):e2304532. doi: 10.1002/adma.202304532. Epub 2023 Sep 22.
The efficient catalysis of nitrogen (N ) into high-value N-containing products plays a crucial role in the N economic cycle. However, weak N adsorption and invalid N activation remain two major bottlenecks in rate-determining steps, leading to low N fixation performance. Herein, an effective dual active sites photocatalyst of polyoxometalates (POMs)-based metal-organic frameworks (MOFs) is highlighted via altering coordination microenvironment and inducing directional shunting of photogenerated carriers to facilitate N /catalyst interaction and enhance oxidation performance. MOFs create more open unsaturated metal cluster sites with unoccupied d orbital possessing Lewis acidity to accept electrons from the 3σ bonding orbital of N for storage by combining with POMs to replace bidentate linkers. POMs act as electron sponges donating electrons to MOFs, while the holes directional flow to POMs. The hole-rich POMs with strong oxidation capacity are easily involved in oxidizing adsorbed N . Taking UiO-66 (C H O Zr ) and Mo Fe ([Mo Fe O (CH COO) {Mo O (H O)} {H Mo O (H O)}(H O) ]·150H O) as an example, Mo Fe @UiO-66 shows twofold enhanced adsorption of N (250.5 cm g ) than UiO-66 (122.9 cm g ) at P/P = 1. And, the HNO yield of Mo Fe @UiO-66 is 702.4 µg g h , ≈7 times and 24 times higher than UiO-66 and Mo Fe . This work provides reliable value for the storage and relaying artificial N fixation.
将氮气（N₂）高效催化转化为高价值含氮产物在氮经济循环中起着关键作用。然而，弱氮吸附和无效氮活化仍然是速率决定步骤中的两个主要瓶颈，导致固氮性能较低。在此，通过改变配位微环境并诱导光生载流子的定向分流，以促进N₂/催化剂相互作用并增强氧化性能，突出了一种基于多金属氧酸盐（POMs）的金属有机框架（MOFs）的有效双活性位点光催化剂。MOFs通过与POMs结合取代双齿连接体，创造了更多具有未占据d轨道的开放不饱和金属簇位点，这些位点具有路易斯酸性，可接受来自N₂的3σ键合轨道的电子进行存储。POMs充当电子海绵向MOFs提供电子，而空穴则定向流向POMs。具有强氧化能力的富空穴POMs很容易参与氧化吸附的N₂。以UiO-66（C₉H₆O₆Zr）和Mo₇Fe₃（[Mo₇Fe₃O₂₀(CH₃COO)₆{MoO₂(H₂O)}₃{H₂MoO₄(H₂O)}(H₂O)₂]·150H₂O）为例，在P/P₀ = 1时，Mo₇Fe₃@UiO-66对N₂的吸附量（250.5 cm³ g⁻¹）比UiO-66（122.9 cm³ g⁻¹）提高了两倍。并且，Mo₇Fe₃@UiO-66的HNO₃产率为702.4 μg g⁻¹ h⁻¹，分别比UiO-66和Mo₇Fe₃高约7倍和24倍。这项工作为人工固氮的存储和中继提供了可靠的价值。
