Abstract Graphdiyne is a new carbon allotrope comprising sp‐ and sp 2 ‐hybridized carbon atoms arranged in a 2D layered structure. In this contribution, 2D graphdiyne is demonstrated to exhibit a strong light–matter interaction with high stability to achieve a broadband Kerr nonlinear optical response, which is useful for nonreciprocal light propagation in passive photonic diodes. Furthermore, advantage of the unique Kerr nonlinearity of 2D graphdiyne is taken and a nonreciprocal light propagation device is proposed based on the novel similarity comparison method. Graphdiyne has demonstrated a large nonlinear refractive index in the order of ≈10 −5 cm 2 W −1 , comparing favorably to that of graphene. Based on the strong Kerr nonlinearity of 2D graphdiyne, a nonlinear photonic diode that breaks time‐reversal symmetry is demonstrated to realize the unidirectional excitation of Kerr nonlinearity, which can be regarded as a significant demonstration of a graphdiyne‐based prototypical application in nonlinear photonics and might suggest an important step toward versatile graphdiyne‐based advanced passive photonics devices in the future.

Kerr Nonlinearity in 2D Graphdiyne for Passive Photonic Diodes