<p>Graphene oxide (GO), owing to its exceptional surface functionality, tunable electronic structure, and excellent dispersibility, has emerged as a versatile platform for the development of advanced composite materials. This review comprehensively examines recent advances in the synthesis strategies of GO-based composites, including covalent and non-covalent functionalization, heterostructure assembly, and hybridization with metal oxides, polymers, and semiconductors. Furthermore, the interfacial interactions and structure-property relationships governing their physicochemical, optoelectronic, and catalytic behaviors are systematically elucidated. Particular emphasis is placed on the photocatalytic performance of GO-based composites in environmental remediation and sustainable energy production. The application of these composites in the degradation of organic pollutants, water splitting, and CO₂ reduction are comprehensively discussed. In addition, key factors influencing photocatalytic efficiency, such as charge-carrier dynamics, band alignment, light absorption, and surface chemistry, are critically discussed. Emerging trends in the design of GO-based photocatalysts with enhanced stability, scalability, and multifunctionality are also highlighted. Finally, current challenges and future research directions, including green synthesis approaches, and real-world application testing, are discussed. By bridging fundamental understanding with technological relevance, this review offers a timely and insightful perspective on the transformative potential of GO-based composites for addressing global water and energy challenges.</p> Graphical abstract <p></p>