• Nanodiamond (ND) offers exceptional chemical stability, high charge carrier mobility, and versatile surface functionalization, positioning it as a promising photocatalyst platform.
• Strategies such as surface functionalization, plasmonic hybridization, heteroatom doping, and heterostructure design effectively extend ND's light absorption into the visible range and enhance charge separation.
• The structure-activity relationship and design principles for ND-based photocatalysts focus on optimizing light harvesting, charge transport, and redox kinetics.
• ND-based photocatalysts show significant potential for solar fuel production (H2, CO2 reduction) and environmental remediation, addressing limitations of conventional photocatalysts.