ZHOU Jingyuan , ZHANG Jin , LIU Zhongfan

1 Center for Nanochemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China.

2 Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R. China.

Abstract: Graphyne is a rapidly rising star material of carbon allotropes containing only sp and sp2 hybridized carbon atoms forming extended twodimensional layers. In particular, graphdiyne is an important member of graphyne family. With unique nanotopological pores, two-dimensional layered conjugated frameworks, and excellent semiconducting and optical properties,graphdiyne has displayed distinct superiorities in the fields of energy storage,electrocatalysis, photocatalysis, nonlinear optics, electronics, gas separation,etc. Therefore, the synthesis of high-quality graphdiyne is highly required to fulfill its potentially extraordinary applications. Furthermore, the development of a standardized and systematic set of characterization procedures is an urgent need, and would be based on intrinsic samples. However, there are still obvious barriers to synthesizing this newborn carbon allotrope that can be mainly considered as follows. The selection and stability of monomers is essential for synthesis. The synthesis process in solution also suffers from an annoying problem of the relatively free rotation possible about the alkyne-aryl single bonds, which leads to the coexistence and rapid equilibration of coplanar and twisted structures.Furthermore, the limited reaction conversion and side reactions also lead to a confusion of configuration.

In this review, we primarily focus on the state-of-the-art progress of the synthetic strategies for graphdiyne. First, we give a brief introduction about the structure of graphyne and graphdiyne. We subsequently discuss in detail the recent developments in synthetic methods that can mainly be divided into three aspects: total organic synthesis, on-surface covalent reaction, and polymerization in a solution phase. In particular, much progress in solution polymerization has been achieved since in-situ polymerization on Cu surface was reported in 2010. Liquid/liquid interface, gas/liquid interface, and surface template were also employed for confined reaction, and contribute significantly to the synthesis of a graphdiyne film. Through such strategies, graphdiyne with a well-defined structure and diverse morphologies could be achieved successfully. Finally, the opportunities and challenges for the synthesis of graphdiyne are prospected. A more rational design is desired in terms of monomer modification and reaction regulation.

Key Words: Graphdiyne; Total synthesis; On-surface covalent reaction; Polymerization in solution phase;Morphology control

1 引言

碳元素是自然界中最具魅力的元素之一，碳材料的发展几乎伴随了整个人类文明史的发展。碳原子位于元素周期表中的第二周期第四主族，其原子核外层有四个价电子，可通过sp、sp2、sp3三种杂化形式的组合构建碳同素异形体，成键形式的多样性也带来了碳材料家族结构和性质的多样性(如图1所示)，尤其是近三十年来，随着纳米材料科学的兴起，涌现出了多种明星纳米碳材料，例如富勒烯、碳纳米管、石墨烯等等，它们在电子学、光学、超导、催化、生物医药等诸多领域中均展现出了重要的应用前景1–3。探索不同杂化形式的碳原子所构成的新型碳同素异形体，发现其中更多新奇的物性，一直是科学家们的追求。

1987年，著名理论学家 Baughman等4首次提出了石墨炔的结构模型，它是仅由sp和sp2两种杂化形式的碳原子组成的二维平面层状结构，理论计算的结果证实了这种结构的稳定性。由于这两种杂化形式有多种组合方式，石墨炔具有丰富的结构多样性，根据其结构的特点，主要可以分为如图 2中所示的四大类：第一类是由碳碳三键连接苯环而成，具有C6对称轴；第二类是除苯环和三键之外，还包含部分碳碳双键，这类结构不符合C6对称性，由于双键的构型使得这类结构具有C2对称轴；第三类是石墨炔结构中不包含苯环，仅由碳碳双键组成，同样不符合C6对称性；第四类结构是不含有苯环，含有一个正六边形的十八元大环，具有 C6对称轴5。石墨炔家族结……