Yang Xiaojian, Chen Feiran, Kim Min A, Liu Haitao, Wolf Lawrence M, Yan Mingdi
Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854, USA.
Department of Chemistry, University of Pittsburgh, 4200 Fifth Ave, Pittsburgh, PA 15260, USA.
Phys Chem Chem Phys. 2022 Aug 31;24(34):20082-20093. doi: 10.1039/d2cp01842j.
The Diels-Alder (DA) reaction, a classic cycloaddition reaction involving a diene and a dienophile to form a cyclohexene, is among the most versatile organic reactions. Theories have predicted thermodynamically unfavorable DA reactions on pristine graphene owing to its low chemical reactivity. We hypothesized that metals like Ni could enhance the reactivity of graphene towards DA reactions through charge transfer. The results indeed showed that metal substrates enhanced the reactivity of graphene in the DA reactions with a diene, 2,3-dimethoxy butadiene (DMBD), and a dienophile, maleic anhydride (MAH), with the activity enhancement in the order of Ni > Cu, and both are more reactive than graphene supported on silicon wafer. The rate constants were estimated to be two times higher for graphene supported on Ni than on silicon wafer. The computational results support the experimentally obtained rate trend of Ni > Cu, both predicted to be greater than unsupported graphene, which is explained by the enhanced graphene-substrate interaction reflected in charge transfer effects with the strongly interacting Ni. This study opens up a new avenue for enhancing the chemical reactivity of pristine graphene through substrate selection.
狄尔斯-阿尔德（DA）反应是一种经典的环加成反应，涉及二烯和亲双烯体形成环己烯，是最通用的有机反应之一。理论预测，由于原始石墨烯的化学反应性较低，其DA反应在热力学上是不利的。我们假设像镍这样的金属可以通过电荷转移提高石墨烯对DA反应的反应性。结果确实表明，金属基底提高了石墨烯在与二烯2,3-二甲氧基丁二烯（DMBD）和亲双烯体马来酸酐（MAH）的DA反应中的反应性，活性增强顺序为Ni>Cu，且两者都比支撑在硅片上的石墨烯更具反应性。据估计，支撑在镍上的石墨烯的速率常数比支撑在硅片上的高两倍。计算结果支持了实验得到的Ni>Cu的速率趋势，两者预计都大于无支撑的石墨烯，这是由与强相互作用的镍的电荷转移效应所反映的增强的石墨烯-基底相互作用来解释的。这项研究为通过基底选择提高原始石墨烯的化学反应性开辟了一条新途径。
