Heterogeneous photocatalysis holds enormous potential to transform a wide array of organic pollutants into relatively innocuous end products. Recently, 3D GBMs have emerged as a promising new class of metal-free photocatalysts, displaying semiconductor-like photoelectric properties and showing excellent photocatalytic performance owing to their unique interconnected structures, tunable porosity, ease of surface functionalization, outstanding electron-transfer efficiency and exceptional light-harvesting capabilities (from deep UV to the near-infrared). In this chapter, recent advances in the rational design of 3D GBM-based photocatalysts are highlighted and their applications in photocatalytic environmental remediation discussed. Additionally, the corresponding reaction mechanisms and pollutant transformation pathways are elucidated to fuel more disruptive and innovative research in this rapidly expanding …