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Templateless Synthesis of Ultra‐Microporous 3D Graphitic Carbon from Cyclodextrins and Their Use as Selective Catalyst for Oxygen Activation
Small Methods ( IF 10.7 ) Pub Date : 2020-01-21 , DOI: 10.1002/smtd.201900721 Alejandra Rendón‐Patiño 1 , Andrea Santiago‐Portillo 1 , Cristina Vallés‐Garcia 1 , Miguel Palomino 1 , Sergio Navalón 1 , Antonio Franconetti 2 , Ana Primo 1 , Hermenegildo Garcia 1
Small Methods ( IF 10.7 ) Pub Date : 2020-01-21 , DOI: 10.1002/smtd.201900721 Alejandra Rendón‐Patiño 1 , Andrea Santiago‐Portillo 1 , Cristina Vallés‐Garcia 1 , Miguel Palomino 1 , Sergio Navalón 1 , Antonio Franconetti 2 , Ana Primo 1 , Hermenegildo Garcia 1
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Pyrolysis of α‐, β‐, and γ‐cyclodextrins at 900 °C gives rise to the formation of crystalline graphitic porous nanoparticles (GCD), where the dimensions of the pores are uniform in the range from 0.63 to 0.97 nm, from Gα‐CD to Gγ‐CD, as determined by transmission electron microscopy. It is found that, while for Gβ‐CD and Gγ‐CD, the surface area measured by N2 adsorption is about 330–550 m2 g−1, respectively, no area can be measured for Gα‐CD with N2 or Ar due to its small pore dimensions. However, CO2 adsorption reveals for Gα‐CD the presence of ultra‐microporosity and a surface area of 727 m2 g−1. GCD exhibits activity as metal‐free catalysts for the aerobic oxidation of alcohols and the activity increases as the pore dimension decreases. Density functional theory calculations indicate that this high catalytic activity for O2 activation derives from confinement effects that favor charge transfer from the graphitic walls to O2. Studies on the formation mechanism shows that the key step leading to the formation of the channels is the melting of cyclodextrin precursors that makes possible the assembly of these capsules before their transformation into microporous graphitic particles.
中文翻译：
环糊精无模板合成超微孔3D石墨碳及其作为氧气活化的选择性催化剂
α-，β-和γ-环糊精在900°C时热解会形成结晶性石墨多孔纳米颗粒（G CD），其中孔的尺寸在从0.63至0.97 nm的范围内是均匀的α-CD到Gγ-CD，由透射电子显微镜确定。结果发现，对于Gβ -CD和Gγ -CD而言，通过N 2吸附测量的表面积分别约为330-550 m 2 g -1，而对于带有N的Gα -CD则无法测量面积。2或Ar的孔径较小。然而，CO 2吸附揭示了G α‐CD超微孔的存在，表面积为727 m 2 g -1。G CD表现出作为无氧催化剂进行酒精好氧氧化的活性，并且随着孔径的减小，活性增加。密度泛函理论计算表明，这种对O 2活化的高催化活性源自限制作用，该作用有利于电荷从石墨壁向O 2转移。对形成机理的研究表明，导致通道形成的关键步骤是环糊精前体的熔融，这使这些胶囊在转化为微孔石墨颗粒之前就可以组装。
更新日期：2020-01-22
中文翻译：
环糊精无模板合成超微孔3D石墨碳及其作为氧气活化的选择性催化剂
α-，β-和γ-环糊精在900°C时热解会形成结晶性石墨多孔纳米颗粒（G CD），其中孔的尺寸在从0.63至0.97 nm的范围内是均匀的α-CD到Gγ-CD，由透射电子显微镜确定。结果发现，对于Gβ -CD和Gγ -CD而言，通过N 2吸附测量的表面积分别约为330-550 m 2 g -1，而对于带有N的Gα -CD则无法测量面积。2或Ar的孔径较小。然而，CO 2吸附揭示了G α‐CD超微孔的存在，表面积为727 m 2 g -1。G CD表现出作为无氧催化剂进行酒精好氧氧化的活性，并且随着孔径的减小，活性增加。密度泛函理论计算表明，这种对O 2活化的高催化活性源自限制作用，该作用有利于电荷从石墨壁向O 2转移。对形成机理的研究表明，导致通道形成的关键步骤是环糊精前体的熔融，这使这些胶囊在转化为微孔石墨颗粒之前就可以组装。
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