Advanced Progress in the Synthesis of Graphdiyne

Graphyne is a rapidly rising star material of carbon allotropes containing only sp and sp(2) hybridized carbon atoms forming extended two-dimensional 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.