南昌大学邓强团队报道了钯单原子负载共价有机框架用于水相氢异解芳醛氢解。相关研究成果发表在2024年11月6日出版的《德国应用化学》。

研究人员开发一种将生物基糠醛串联氢解为甲基呋喃的方法，其对于合成可持续的生物燃料和化学品至关重要。然而，由于C=C键易于氢化，C-O键难以断裂，带来了挑战。

该文中，研究人员制备了一种钯（Pd）单原子支撑的共价有机框架，当在30°C下与5-甲基呋喃醛在前所未有的水溶剂中反应时，其2,5-二甲基呋喃的收率高达98.2%。此外，它在室温下转化各种糠醇、苄基和杂环醛时表现出优异的催化通用性。

对催化机理的分析证实，H₂在Pd-N对上被异质激活，引发共价有机框架（COFs）主体的酮-烯醇互变异构，导致H-PdO-H⁺位点。这些位点通过稀有的SN2机制，为C=O基团提供了新的不对称氢化位点，为C-OH基团提供了氢解位点。

该研究通过COF催化剂的H₂诱导酮-烯醇互变异构，在室温下在水溶剂中非典型制备甲基芳烃，证明了显著的双功能催化作用。

附：英文原文

Title: Palladium Single Atom-supported Covalent Organic Frameworks for Aqueous-phase Hydrogenative Hydrogenolysis of Aromatic Aldehydes via Hydrogen Heterolysis

Author: Zhihao Ouyang, Guan Sheng, Yao Zhong, Jun Wang, Jianxin Cai, Shuguang Deng, Qiang Deng

Issue&Volume: 2024-11-06

Abstract: Developing a method for the tandem hydrogenative hydrogenolysis of bio-based furfuryl aldehydes to methylfurans is crucial for synthesizing sustainable biofuels and chemicals; however, it poses a challenge due to the easy hydrogenation of the C=C bond and difficult cleavage of the C–O bond. Herein, a palladium (Pd) single-atom-supported covalent organic framework was fabricated and showed a unique 2,5-dimethylfuran yield of up to 98.2% when reacted with 5-methyl furfuryl aldehyde in an unprecedented water solvent at 30°C. Furthermore, it exhibited excellent catalytic universality while converting various furfuryl-, benzyl-, and heterocyclic aldehydes at room temperature. The analysis of the catalytic mechanism confirmed that H2 was heterolytically activated on the Pd–N pair and triggered the keto-enol tautomerism of the covalent organic frameworks (COFs) host, resulting in H––PdO–H+ sites. These sites served as novel asymmetric hydrogenation sites for the C=O group and hydrogenolysis sites for the C–OH group through a scarce SN2 mechanism. This study demonstrated remarkable bifunctional catalysis through the H2-induced keto-enol tautomerism of COF catalysts for the atypical preparation of methyl aromatics in a water solvent at room temperature.

DOI: 10.1002/anie.202418790

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202418790