Graphdiyne (GDY)/two-dimensional materials (2DMs) heterostructures present unique opportunities for advanced optoelectronic and neuromorphic devices because of their exceptional electrical, optical, and structural properties. However, the traditional methods for construction of GDY/2DMs heterostructures usually lead to inferior interfaces, which seriously affects the charge separation and transport. Herein, an in situ approach for growing GDY nanowalls (NWs) on WSe2 is employed in this work. The as-prepared GDY NWs/WSe2 heterostructure exhibits self-powered broadband photodetection across 405–980 nm with a high responsivity of 2176 A/W and detectivity of 3.6 × 1012 Jones at 532 nm under 0.02 mW/cm2 illumination, significantly outperforming previously reported GDY-based devices. The efficient charge separation and strong photocarrier trapping in the GDY NWs/WSe2 heterostructure result in pronounced short-term and long-term synaptic plasticity. The nonlinear, wavelength-dependent reservoir state separation enables clear distinction of multiple pulse sequences, which shows great potential for logic processing. The successfully resolved red, green, and violet patterns, and one-shot color image recognition of a 5-letter image highlight transformative potential of GDY NWs/WSe2 device for future adaptive imaging and neuromorphic computing technologies.