Zhang Xiaofei, Yang Caoyu, An Pengfei, Cui Chengqian, Ma Yumiao, Liu Haitao, Wang Hui, Yan Xiaoying, Li Guodong, Tang Zhiyong
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Sci Adv. 2022 Oct 7;8(40):eadd5678. doi: 10.1126/sciadv.add5678.
Numerous efforts are being made toward constructing artificial nanopockets inside heterogeneous catalysts to implement challenging reactions that are difficult to occur on traditional heterogeneous catalysts. Here, the enzyme-mimetic nanopockets are fabricated inside the typical UiO-66 by coordinating zirconium nodes with terephthalate (BDC) ligands and monocarboxylate modulators including formic acid (FC), acetic acid (AC), or trifluoroacetic acid (TFA). When used in transfer hydrogenation of alkyl levulinates with isopropanol toward γ-valerolactone (GVL), these modulators endow zirconium sites with enhanced activity and selectivity and good stability. The catalytic activity of UiO-66FC is ~30 times that of UiO-66, also outperforming the state-of-the-art heterogeneous catalysts. Distinct from general consensus on electron-withdrawing or electron-donating effect on the altered activity of metal centers, this improvement mainly originates from the conformational change of modulators in the nanopocket to assist forming the rate-determining six-membered ring intermediate at zirconium sites, which are stabilized by van der Waals force interactions.
人们正在做出诸多努力，试图在多相催化剂内部构建人工纳米口袋，以实现传统多相催化剂上难以发生的具有挑战性的反应。在此，通过将锆节点与对苯二甲酸（BDC）配体以及包括甲酸（FC）、乙酸（AC）或三氟乙酸（TFA）在内的单羧酸调节剂配位，在典型的UiO-66内部制备了仿酶纳米口袋。当用于将乙酰丙酸酯与异丙醇转移加氢生成γ-戊内酯（GVL）时，这些调节剂赋予锆位点更高的活性、选择性和良好的稳定性。UiO-66FC的催化活性约为UiO-66的30倍，也优于目前最先进的多相催化剂。与关于吸电子或给电子对金属中心活性改变的普遍共识不同，这种改进主要源于纳米口袋中调节剂的构象变化，以协助在锆位点形成决定反应速率的六元环中间体，这些中间体通过范德华力相互作用得以稳定。
