An emerging carbon allotrope: Graphyne−from diverse structures, controllable synthesis, and systematic characterizations to multifunctional applications

As a frontier complement and extension to the well-developed graphdiyne, graphyne (GY) is a distinctive carbon allotrope featuring single acetylene (−C≡C−) linkages bridging adjacent benzene rings, which represents a cutting-edge direction in the development of emerging two-dimensional carbon materials. This review first summarizes the structural classification, lattice parameters, and intrinsic properties of GY based on theoretical calculations. The controllable synthesis methods for almost all GY are then categorized by precursor type—including CaC₂‑mediated nucleophilic/mechanochemical routes, transition metal(TM)‑catalyzed cross‑coupling polymerization, metal‑free nucleophilic aromatic substitution, dynamic alkyne metathesis—with critical discussion of their respective advantages, limitations, and underlying mechanisms. Furthermore, we provide a detailed summary of characterization techniques covering structural, compositional, and additional advanced analyses, alongside a thorough overview of multifunctional applications covering supercapacitors, batteries, photo-/electro-catalysis, and nonlinear optics. Finally, this review critically assesses the key challenges and future opportunities spanning from GY synthesis to practical applications, emphasizing the urgent need for direct experimental evidence to elucidate the crucial role of −C≡C− bonds in different applications.