TiO₂ semiconductors exhibit a low catalytic activity level under visible light because of their large band gap and fast recombination of electron–hole pairs. This paper reports the simple fabrication of a 0D/2D heterojunction photocatalyst by anchoring TiO₂ quantum dots (QDs) on graphite-like C₃N₄ (g-C₃N₄) nanosheets (NSs); the photocatalyst is denoted as TiO₂ QDs@g-C₃N₄. The nanocomposite was characterized via analytical instruments, such as powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, t orange (MO) under solar light were compared. The TiO₂ QDs@g-C₃N₄ photocatalyst exhibited 95.57% MO degradation efficiency and ~3.3-fold and 5.7-fold higher activity level than those of TiO₂ QDs and g-C₃N₄ NSs, respectively. Zero-dimensional/two-dimensional heterojunction formation with a staggered electronic structure leads to the efficient separation of photogenerated charge carriers via a Z-scheme pathway, which significantly accelerates photocatalysis under solar light. This study provides a facile synthetic method for the rational design of 0D/2D heterojunction nanocomposites with enhanced solar-driven catalytic activity.