【摘要】 碳催化是一类以碳材料本身为催化剂,无需金属或金属氧化物作为活性位参与的绿色催化过程,具有无毒无害的优势,该路线尤其适用于食品、生物、医药等相关领域化学品的合成,具有很大的发展潜力.碳材料的孔隙结构和可接触活性位的数量是制备高效碳基催化剂的关键,然而由于C–C键固有的稳定性,碳材料表面通常呈惰性,活性中心仅存在于sp²杂化碳表面边缘的缺陷处,但很多碳材料中这种边缘位置相当有限.为了获得更多的活性位,常采用浓HNO₃和H₂O₂对碳材料进行苛刻的氧化处理,该方法不仅带来严重的环境问题,同时还会破坏碳材料原有的孔隙结构,因此需要从合成角度出发,探索制备具有高密度活性位的碳基催化材料的新方法.作为一种绿色可再生资源,生物质无疑是最理想的碳前驱体,但在高温炭化过程中,其自身的氧元素很容易失去,如何在构建多孔炭过程中有效保护氧物种,并最终形成有效的含氧活性位仍然面临挑战.本文以生物质作为碳源,提出一种界面诱导策略构建和提升生物质基多孔炭（记作Bio-PC）本征活性位,将铝盐（主要是硝酸铝）与生物质（如淀粉等）混合形成铝盐/淀粉界面,高温炭化过程中形成氧化铝/炭界面,开发制备高活性的碳催化剂.氧化铝一方面可起到硬模板的作用,另一方面由于铝和炭之间的界面相互作用,部分氧基团被保护下来.在该过程中,氧化铝/炭界面可被视为保护含氧官能团的摇篮,在铝物种去除后,这些含氧官能团得以有效地暴露.研究表明,在没有任何氧化处理的情况下, Bio-PC上的表面氧官能团的数量可以达到1.27 mmol·g^-1,明显高于熟知的基于传统硬模板法制备的CMK-3材料(0.24 mmol·g^-1).Bio-PC在催化胺氧化偶联合成亚胺（一类重要的药物中间体）反应中表现出优异的催化活性和选择性,其活性是氧化石墨催化剂的22倍.采用核磁共振和X射线光电子能谱技术等多种表征手段研究了氧化铝/炭界面在构建多孔炭过程中发挥的重要作用,并关联了反应活性与表面活性位数量间的关系.还可以根据本文策略在合成体系中简单引入其他组分,如磷酸、柠檬酸等,使所制备炭材料的孔径在微孔到介孔范围内有效调节,获得适用于催化不同分子大小反应物的多孔炭.综上,本工作将为开发高性能的碳基非金属催化剂提供新的思路.更多还原

【Abstract】 Carbon catalysis is an attractive metal-free catalytic transformation, and its performance is significantly dependent on the number of accessible active sites. However, owing to the inherent stability of the C–C linkage, only limited active sites at the edge defects of the basal plane can be obtained even after a harsh oxidation treatment. In this study, the concept of interfacial interactions was adopted to propose an efficient strategy to develop highly active carbon catalysts. The alumi-na/carbon interface formed in situ acted as a cradle for the generation of oxygen-containing functional groups. In the absence of oxidation treatment, the concentration of oxygen-containing functional groups and the specific surface area can reach 1.27 mmol·g^–1 and 2340 m²·g^–1, respectively, which are significantly higher than those of carbon prepared by traditional hard template methods. This active carbon shows a significant enhancement in catalytic performance in the oxidative coupling of amine to imine, about 22-fold higher than that of a well-known graphite oxide catalyst. Such interfacial interaction strategies are based on sustainable carbon sources and can effectively tune the porous structure of carbon in the micro-and meso-ranges. This conceptual finding offers new opportunities for the development of high-performance carbon-based metal-free catalysts.更多还原