Covalent organic frameworks (COFs) are being explored as promising candidates for solar photocatalysis, specifically for solar-driven water splitting to produce hydrogen. While COF-based photocatalysts have shown potential, challenges such as poor charge carrier separation and high exciton binding energy limit their efficiency. Constructing heterojunctions is found to enhance charge carrier separation efficiency in COF-based semiconductors. The ground-state charge transfer (GSCT) mechanism, which facilitates electron transfer and reduces recombination, plays a crucial role in improving charge separation within COFs. Recent research focuses on synthesizing and studying FOOCOF-based heterojunction photocatalysts, including three-dimensional stacked COF-based S-scheme heterojunctions and co-planar single-molecule junctions. Studies reveal that single-molecule junctions featuring covalent bonding exhibit a stronger GSCT effect, enhancing exciton dissociation and carrier migration. Experimental and theoretical analyses confirm the improved performance of COF-PDI in photocatalytic hydrogen production under visible light irradiation. The synthesis and characterization of the COF photocatalysts, along with the demonstration of their photocatalytic activity, showcase the potential of COFs in advancing solar-driven hydrogen production.