Wang Wenjing, Zhang Ling, Jia Taikang, Jiang Bei, Xu Mengya, Li Ruofan, Zhang Chuanqi, Wang Wenzhong
State Key Laboratory of High Performance Ceramics, Shanghai Institute of Ceramics Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai, 200050, P. R. China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing, 100049, China.
ChemSusChem. 2025 Sep 26:e202501492. doi: 10.1002/cssc.202501492.
The selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a key monomer for degradable plastics, is crucial for biomass valorization and addressing plastic pollution. However, its efficiency is limited by high energy barriers and slow kinetics due to the complex multi-electron and multi-proton transfer steps. Herein, a MIL-100(Fe)/TEMPO/nitric acid catalyst system is developed to facilitate electron transfer in HMF oxidation. The catalyst system achieves 100% conversion of 3 wt% HMF in 16 h at 353 K and atmospheric pressure, with a 94% yield of total acid product. The cyclic voltammetry and in situ electron paramagnetic resonance (EPR) reveal that nitric acid promotes TEMPO oxidation to TEMPO, facilitating electron transfer and increasing the oxidation rate. The Griess method, ferrocene cation probe, and in situ EPR confirm nitric oxide (NO) formation, which acts as an electron shuttle between oxygen and MIL-100(Fe), accelerating the Fe(III)/Fe(II) redox cycle. Hydrogen/deuterium kinetic isotope effect analysis supports a proton-coupled electron transfer (PCET) mechanism. This study demonstrates that nitric acid significantly enhances PCET, enabling rapid oxidation of HMF to FDCA under mild conditions.
将生物质衍生的5-羟甲基糠醛（HMF）选择性氧化为2,5-呋喃二甲酸（FDCA，一种可降解塑料的关键单体）对于生物质增值和解决塑料污染至关重要。然而，由于复杂的多电子和多质子转移步骤，其效率受到高能垒和缓慢动力学的限制。在此，开发了一种MIL-100(Fe)/TEMPO/硝酸催化剂体系，以促进HMF氧化中的电子转移。该催化剂体系在353 K和大气压下16小时内实现了3 wt% HMF的100%转化，总酸产物产率为94%。循环伏安法和原位电子顺磁共振（EPR）表明，硝酸促进TEMPO氧化为TEMPO⁺，促进电子转移并提高氧化速率。格里斯方法、二茂铁阳离子探针和原位EPR证实了一氧化氮（NO）的形成，其作为氧与MIL-100(Fe)之间的电子穿梭体，加速了Fe(III)/Fe(II)氧化还原循环。氢/氘动力学同位素效应分析支持质子耦合电子转移（PCET）机制。本研究表明，硝酸显著增强了PCET，能够在温和条件下将HMF快速氧化为FDCA。
