2D conjugated metal-organic frameworks (MOFs) have attracted significant attention in various fields due to their outstanding characteristics. However, due to the strong interlayer π-π stacking interactions, the preparation of high-quality and atomic-scale single-crystalline conjugated MOF structures continues to pose a significant challenge. The investigation of its nonlinear optical (NLO) property and application for ultrafast photonics is still rare. Herein, the ultrathin Cu