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首页> 外文期刊>Electrocatalysis >Polymer of Intrinsic Microporosity Induces Host-Guest Substrate Selectivity in Heterogeneous 4-Benzoyloxy-TEMPO-Catalysed Alcohol Oxidations
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Polymer of Intrinsic Microporosity Induces Host-Guest Substrate Selectivity in Heterogeneous 4-Benzoyloxy-TEMPO-Catalysed Alcohol Oxidations

机译：本征微孔性的聚合物在多相4-苯甲酰氧基-TEMPO催化的醇氧化反应中诱导主宾基质的选择性。

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摘要

The free radical 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4B-TEMPO) is active as an electrocatalyst for primary alcohol oxidations when immobilised at an electrode surface and immersed into an aqueous carbonate buffer solution. In order to improve the catalytic process, a composite film electrode is developed based on (i) carbon microparticles of 2-12 mu m diameter to enhance charge transport and (ii) a polymer of intrinsic microporosity (here PIM-EA-TB with a BET surface area of 1027 m(2) g(-1)). The latter acts as a highly rigid molecular framework for the embedded free radical catalyst with simultaneous access to aqueous phase and substrate. The resulting mechanism for the oxidation of primary alcohols is shown to switch in reaction order from first to zeroth with increasing substrate concentration consistent with a kinetically limited process with competing diffusion of charge at the polymer layer-electrode interface (here the "LEk" case in Albery-Hillman notation). Reactivity optimisation and screening for a wider range of primary alcohols in conjunction with DFT-based relative reactivity correlation reveals substrate hydrophobicity as an important factor for enhancing catalytic currents. The PIM-EA-TB host matrix is proposed to control substrate partitioning and thereby catalyst reactivity and selectivity.
机译：自由基4-苯甲酰氧基-2,2,6,6-四甲基哌啶-1-氧基（4B-TEMPO）固定在电极表面并浸入碳酸盐缓冲水溶液中时，可作为伯醇氧化的电催化剂。为了改善催化过程，开发了一种复合膜电极，该复合膜电极基于（i）直径为2-12微米的碳微粒以增强电荷传输，以及（ii）具有固有微孔性的聚合物（此处为PIM-EA-TB，具有BET表面积为1027 m（2）g（-1））。后者充当嵌入式自由基催化剂的高刚性分子框架，同时可接触水相和底物。结果表明，生成的伯醇氧化机理随着反应物浓度从高到低依次从第一顺序切换到零，这与在聚合物层-电极界面处电荷竞争扩散的动力学受限过程（此处为“ LEk”情况） Albery-Hillman表示法）。结合最广泛的伯醇进行的反应性优化和筛选以及基于DFT的相对反应性相关性表明，底物疏水性是增强催化电流的重要因素。提出了PIM-EA-TB基质，以控制底物分配，从而控制催化剂的反应性和选择性。

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