As a sustainable and green approach, carbocatalysis, a metal-free strategy, has shown exceptional results in advanced oxidation processes (AOPs). Nonetheless, the recovery of these catalysts has been a major shortcoming over the years. Herein, three-dimensional nitrogen-doped graphene macrostructures (3D-NGMs), in the form of macro cubes, were synthesised by a simple cross-linking and thermal annealing procedure, after which they were employed in the activation of peroxydisulfate (PS) for the degradation of sulfamethoxazole (SMX). The catalytic cubes were loaded with different amounts of nitrogen precursor to investigate the role of nitrogen configuration in the sp2 hybridised carbon network on AOPs. NGC3 cubes with optimum N-loading exhibited outstanding performance for SMX degradation owing to their optimum N/C ratio. Various reaction parameters were studied to optimise the catalytic system. Comprehensive studies on the radical generation were done and illustrated the dominance of the non-radical pathway leading to the proposal of a possible reaction mechanism for SMX. This study not only suggests the role of nitrogen doping on graphene macrostructures but also provides novel insights into macro catalysis to overcome the recovery challenges posed by nano catalysis.