通过非原位 X 射线吸收光谱和原位衰减全反射红外研究阐明杂多酸/铜金属有机骨架催化剂选择性氧化 5-羟甲基糠醛的活性位点和机理途径,ACS Catalysis

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通过非原位 X 射线吸收光谱和原位衰减全反射红外研究阐明杂多酸/铜金属有机骨架催化剂选择性氧化 5-羟甲基糠醛的活性位点和机理途径
ACS Catalysis ( IF 11.3 ) Pub Date : 2023-04-18 , DOI: 10.1021/acscatal.3c00872
Paramita Koley ₁ , Subhash Chandra Shit ₂ , Takefumi Yoshida _{3,

4} , Hiroko Ariga-Miwa _{3,

4} , Tomoya Uruga _{3,

4,

5} , Tayebeh Hosseinnejad ₁ , Selvakannan Periasamy ₁ , Su-Il In ₂ , Dharmendra D. Mandaliya ₆ , Ravindra D. Gudi ₇ , Yasuhiro Iwasawa _{3,

4,

8} , Suresh K. Bhargava ₁

Affiliation

在无碱条件下，5-羟甲基糠醛 (HMF) 在非贵金属上化学选择性氧化生成生物塑料单体 2,5-呋喃二甲酸 (FDCA) 具有挑战性，值得研究。HMF 氧化成 FDCA 涉及伯醇和醛官能团同时氧化成羧基，因此需要包含双活性位点和 HMF 化学选择性氧化的双功能催化剂。目前的工作证明了在由 Cu-BTC（金属有机骨架（MOF））和多金属氧酸盐（POM）组成的复合多孔材料（Cu-BTC_PMA）中形成了新的选择性活性位点。多孔框架提供 (Cu-BTC_PMA) 所需的化学选择性，而 Cu-BTC (MOF) 和 Cu-O-Mo 位点中的选择性 Cu 金属中心充当将 HMF 同时氧化为 FDCA 的活性位点。该催化剂在无碱和温和的反应条件下表现出 89% 的 HMF 转化率和 92.3% 的 FDCA 选择性。详细而言，X 射线吸收光谱分析证明了 MOF 和 POM 在分子水平上的化学键调整以及电子结构调制，这指导了新的协同界面活性位点和电荷转移态的形成。这种现象导致铜独特的氧化还原环境和多种氧化态以及 Cu-BTC_PMA 催化剂中的氧空位的产生，这很可能表现为无碱氧化的活性位点。随后使用原位衰减全反射红外光谱对该反应进行了动力学研究，证明了导致 FDCA 形成的特定中间体的稳定性。此外，我们对反应物（HMF）与Cu-BTC和Cu-BTC_PMA两种催化剂模型之间的表面相互作用进行了比较密度泛函理论和分子原子量子理论研究，以定量解释Cu-BTC_PMA的较高催化活性催化剂。动力学研究还评估了多步氧化反应的决速步骤和活化能。我们对反应物（HMF）与Cu-BTC和Cu-BTC_PMA两种催化剂模型之间的表面相互作用进行了比较密度泛函理论和分子中原子量子理论研究，以定量解释Cu-BTC_PMA催化剂的较高催化活性。动力学研究还评估了多步氧化反应的决速步骤和活化能。我们对反应物（HMF）与Cu-BTC和Cu-BTC_PMA两种催化剂模型之间的表面相互作用进行了比较密度泛函理论和分子中原子量子理论研究，以定量解释Cu-BTC_PMA催化剂的较高催化活性。动力学研究还评估了多步氧化反应的决速步骤和活化能。

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Elucidation of Active Sites and Mechanistic Pathways of a Heteropolyacid/Cu-Metal–Organic Framework Catalyst for Selective Oxidation of 5-Hydroxymethylfurfural via Ex Situ X-ray Absorption Spectroscopy and In Situ Attenuated Total Reflection-Infrared Studies

Chemoselective oxidation of 5-hydroxymethylfurfural (HMF) over non-noble metals to produce a bioplastic monomer, 2,5-furandicarboxylic acid (FDCA), under alkaline-free conditions is challenging and worthy of investigation. HMF oxidation into FDCA involves the concurrent oxidation of primary alcohol and an aldehyde functional group into carboxylic groups, which therefore demand a bifunctional catalyst containing dual active sites and chemoselective oxidation of HMF. The present work demonstrated the formation of new selective active sites in a composite porous material (Cu-BTC_PMA) that consists of Cu-BTC (metal–organic framework (MOF)) and polyoxometalate (POM). The porous framework provides (Cu-BTC_PMA) the desired chemoselectivity, while a selective Cu metal center in Cu-BTC (MOF) and Cu–O–Mo sites functions as active sites for the concurrent oxidation of HMF into FDCA. This catalyst exhibited a HMF conversion of 89% and an FDCA selectivity of 92.3% under base-free and mild reaction conditions. In detail, X-ray absorption spectroscopy analysis demonstrated the chemical bond tuning, as well as electronic structural modulations of MOF and POM at the molecular level, which directs the formation of new synergistic interfacial active sites and charge transfer states. This phenomenon causes the generation of the unique redox environment of copper and the multiple oxidation states along with the oxygen vacancy in the Cu-BTC_PMA catalyst, which most likely behaves as active sites for base-free oxidation. A kinetics study of this reaction was followed using in situ attenuated total reflection-infrared spectroscopy, demonstrating the stabilization of the specific intermediates that lead to the formation of FDCA. Moreover, we made comparative density functional theory and quantum theory of atoms in molecules investigations on the surface interaction between the reactant (HMF) and two catalyst models of Cu-BTC and Cu-BTC_PMA to interpret quantitatively the higher catalytic activity of the Cu-BTC_PMA catalyst. The kinetics study also evaluates the rate-determining step and activation energy for the multistep oxidation reactions.

更新日期：2023-04-18

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