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

• Published in: Angewandte Chemie International Edition Vol. 64; no. 6; pp. e202418790 - n/a
• Main Authors: Ouyang, Zhihao, Sheng, Guan, Zhong, Yao, Wang, Jun, Cai, Jianxin, Deng, Shuguang, Deng, Qiang
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 03.02.2025
• Edition: International ed. in English
• Subjects: Aldehydes; aromatic aldehydes; Aromatic compounds; Biofuels; Catalysis; Catalytic converters; Chemical bonds; Covalence; covalent organic framework; Hydrogenation; hydrogenative hydrogenolysis; Hydrogenolysis; keto-enol tautomerism; methyl aromatics; Palladium; Room temperature; Solvents; Tautomerism; aromatic aldehydes; keto-enol tautomerism; methyl aromatics; hydrogenative hydrogenolysis; covalent organic framework
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202418790

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−−Pd⋅⋅⋅O−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. In situ‐generated H+−H− pairs by hydrogen heterolysis on palladium single atom‐supported covalent organic framework act as hydrogenation sites for C=O group and hydrogenolysis sites for C−OH group. The close intimate hydrogenation and acid sites show unprecedented hydrogenative hydrogenolysis route of aromatic aldehydes in a water solvent at room temperature.