Visualizing stepwise evolution of carbon hybridization from sp3 to sp2 and to sp
Wei Xiong, Guang Zhang, De‐Liang Bao, Jianchen Lu, Lei Gao, Yusen Li, Hui Zhang, Zilin Ruan, Zhenliang Hao, Hong-Jun Gao, Long Chen, Jinming Cai
Abstract
Abstract Regulating carbon hybridization states lies at the heart of engineering carbon materials with tailored properties but orchestrating the sequential transition across three states has remained elusive. Here, we visiualize stepwise evolution in carbon hybridizations from sp ³ to sp ² and to sp states via dehydrogenation and elimination reactions of methylcyano-functionalized molecules on surfaces. Utilizing scanning probing microscopy, we distinguish three distinct carbon-carbon bond types within polymers induced by annealing at elevated temperatures. Density-functional-theory calculations unveil the pivotal role of the electron-withdrawing cyano group in activating neighboring methylene to form C( sp 3 )–C( sp 3 ) bonds, and in facilitating subsequent stepwise HCN eliminations to realize the transformation across three carbon-carbon bond types. We also demonstrate the applicability of this strategy on one-dimensional molecular wires and two-dimensional covalent organic framework on different substrates. Our work expands the scope of carbon hybridization evolution and serves as an advance in flexibly engineering carbon-material by employing cyanomethyl-substituted molecules.