Mukadam Zamaan, Liu Sihang, Scott Soren B, Zhou Yuxiang, Kastlunger Georg, Ryan Mary P, Titirici Maria Magdalena, Stephens Ifan E L
Department of Materials, Imperial College London, London SW7 2AZ, United Kingdom.
Catalysis Theory Center, Department of Physics, Technical University of Denmark (DTU), 2800 Kgs. Lyngby, Denmark.
ACS Electrochem. 2025 Mar 14;1(5):699-708. doi: 10.1021/acselectrochem.4c00171. eCollection 2025 May 1.
The electrochemical synthesis of nitrogen-containing molecules from biomass-derived compounds under ambient conditions is demonstrated, relying only on green sources of feedstock, renewable energy, and water. In this study, we report a two-step method of electrochemically synthesizing 5-(aminomethyl)furan-2-carboxylic acid (AFCA) from 5-hydroxymethylfurfural (HMF) using hydroxylamine (NHOH) as the nitrogen source in an acidic electrolyte. In the first step, HMF was reductively aminated into (5-(aminomethyl)furan-2-yl)methanol (HMFA) using NHOH as the source of nitrogen. This was followed by a second step, involving the oxidation of HMFA to AFCA on a manganese oxide (MnO ) anode at the same pH. MnO was able to selectively oxidize the alcohol group on HMFA to produce AFCA with 35% Faradaic efficiency without affecting the amine group. As both of these reactions are completed in a pH 1 electrolyte, it eliminates the need to separate HMFA before proceeding with the second reaction. Among different metal electrodes (Ag, Au, Cu, Pb, Pt and Sn) tested for the electrochemical reductive amination reaction, Ag electrodes displayed the best performance to selectively aminate HMF to the intermediate species, HMFA, with up to 69% Faradaic efficiency at mild potentials of -0.50 V. Density functional theory calculations were carried out to explore a possible reaction pathway for the reductive amination on Ag(111), which suggests a thermodynamically feasible reaction even at 0 V. The cathodic experimental reaction parameters were optimized to reveal that an electrolyte pH of 1 is optimal for the electrochemical reductive amination reaction. Our work shapes the future possibility of an electrochemical synthesis to produce AFCA without the need for any product separation between steps by combining the Ag cathode reaction to the MnO anode reaction sharing the same electrolyte. Since both the cathode and anode reactions both involve four electrons transferred, combining both half reactions in a single electrochemical reactor can eliminate the need for energy-wasting auxiliary counter reactions such as hydrogen evolution or water oxidation.
本文展示了在环境条件下，仅依靠绿色原料、可再生能源和水，从生物质衍生化合物中电化学合成含氮分子的方法。在本研究中，我们报道了一种两步法，即在酸性电解质中，以羟胺（NHOH）作为氮源，从5-羟甲基糠醛（HMF）电化学合成5-（氨甲基）糠酸（AFCA）。第一步，使用NHOH作为氮源，将HMF还原胺化生成（5-（氨甲基）呋喃-2-基）甲醇（HMFA）。第二步，在相同pH值下，在氧化锰（MnO ）阳极上，将HMFA氧化为AFCA。MnO 能够选择性地氧化HMFA上的醇基，以35%的法拉第效率生成AFCA，而不影响胺基。由于这两个反应均在pH为1的电解质中完成，因此无需在进行第二步反应之前分离HMFA。在测试的用于电化学还原胺化反应的不同金属电极（Ag、Au、Cu、Pb、Pt和Sn）中，Ag电极表现出最佳性能，能够在-0.50 V的温和电位下，以高达69%的法拉第效率将HMF选择性胺化为中间物种HMFA。进行了密度泛函理论计算，以探索Ag(111)上还原胺化的可能反应途径，结果表明即使在0 V时，该反应在热力学上也是可行的。对阴极实验反应参数进行了优化，结果表明电解质pH为1对于电化学还原胺化反应是最佳的。我们的工作通过将Ag阴极反应与MnO 阳极反应结合在同一电解质中，为无需在步骤之间进行任何产物分离即可电化学合成AFCA创造了未来可能性。由于阴极和阳极反应均涉及四个电子转移，在单个电化学反应器中结合这两个半反应可以消除诸如析氢或水氧化等耗能辅助对映反应的需要。
