The supercritical CO₂ (scCO₂)-subcritical H₂O (subH₂O) system offers a metal- and additive-free reaction solvent that can be used for organic synthesis. The enhanced formation of carbonic acid and ionization of water under elevated pressures and temperatures promote the production of hydronium and hydroxyl ions that can catalyze the conversion of a number of organic compounds. Furthermore, the biphasic nature of the system allows for the simultaneous extraction of less polar products from the aqueous solution by a flowing scCO₂ stream. In this study, we investigated the use of scCO₂-subH₂O as a reactive separation medium for the conversion of glucose to 5-hydroxymethylfurfural (HMF). The highest HMF yield achieved was 32.6 % with a selectivity of 52.7 %. These values corresponded to a 20.25 % and 41.9 % increase in the yield and selectivity that were achieved in the experiments performed under batch operations. The improvement was primarily attributed to the extraction of some of the HMF from the solution. The highest separation efficiency so far was 12.7 %. We also performed semi-empirical quantum calculations to determine a possible mechanism of the production of HMF from glucose. The two-step process, which involved the isomerization of glucose to fructose and the dehydration of fructose to HMF, was shown to proceed with only the OH^– and H₃O⁺ that are inherent in the solvent system as catalysts. Insights from both kinetic data and quantum calculations revealed that the reaction is highly favored in the acidic environment of the scCO₂-subH₂O system.

超临界CO ₂（scCO ₂）-亚临界H ₂ O（subH ₂ O）系统提供了无金属和无添加剂的反应溶剂，可用于有机合成。在升高的压力和温度下碳酸形成的增强和水的电离促进了水合氢根离子和氢氧根离子的产生，它们可以催化许多有机化合物的转化。此外，该系统的双相性质允许通过流动的scCO ₂流同时从水溶液中提取极性较小的产物。在这项研究中，我们调查了使用SCCO的₂ -subH ₂O作为反应性分离介质，用于将葡萄糖转化为5-羟甲基糠醛（HMF）。达到的最高HMF产率为32.6％，选择性为52.7％。这些值对应于在分批操作下进行的实验中实现的产率和选择性的20.25％和41.9％的增加。改进主要归因于从溶液中提取了一些HMF。迄今为止，最高分离效率为12.7％。我们还进行了半经验量子计算，以确定由葡萄糖生产HMF的可能机理。两个步骤的过程，其中涉及葡萄糖果糖和果糖为HMF脱水的异构化中，示出仅与OH进行^-和H ₃ ö ⁺溶剂体系中固有的催化剂。来自两个动力学数据和量子计算的见解，发现该反应在SCCO的酸性环境中的高度青睐₂ -subH ₂ O系统。