Hybrid two-dimensional (2D) materials composed of carbon, boron, and nitrogen constitute a hot topic of research, as their flexible composition allows for tunable properties. However, while graphene-like hybrid lattices have been well characterized, systematic investigations are lacking for various 2D materials. Hence, in the present contribution, we employ first-principles calculations to investigate the structural, electronic and optical properties of what we call B x C y N z hybrid a-graphynes. We considered eleven structures with stoichiometry BC 2 N and varied atomic arrangements. We calculated the formation energy for each arrangement, and determined that it is low (high) when the number of boron-carbon and nitrogencarbon bonds is low (high). We found that the formation energy of many our structures compared favorably with a previous literature proposal. Regarding the electronic properties, we found that the investigated structures are semiconducting, with band gaps ranging from 0.02 to 2.00 eV. Moreover, we determined that most of the B x C y N z hybrid a-graphynes proposed here strongly absorb infrared light, and so could potentially find applications in optoelectronic devices such as heat sensors and infrared filters.Additional applications proposed for graphynes include: energy storage, 38 use as battery anodes, 39 gas separation, 40 and water desalination. 41 Boron nitride analogues of the a-, b-, g-, and 6, 6, 12-graphynes have also been investigated. [42][43][44] These structures, termed BNynes, are formed by the combination of BN hexagonal rings with BN linear chains (. -B^N-B^N-.). First-Fig. 1 Illustration of the optimized B x C y N z hybrid a-graphynes with different atomic arrangements.This journal is Fig. 8 Optimized B-C-N hybrid a-graphyne nanoribbon with armchair edge. The calculated band structure and the projected density of states (PDOS) are also shown. The Fermi energy E f is indicated by the horizontal dotted line.This journal is