<p>Visible light-responsive CdFe₂O₄ photocatalysts were synthesized via a one-step combustion route using a series of structurally distinct carboxylic acid-based fuels, enabling deliberate modulation of nanostructure and optoelectronic properties. The functional groups and molecular architecture of the fuels played a crucial role in governing combustion behavior, which in turn dictated crystallite growth, surface morphology, and bandgap tuning in the resulting CdFe₂O₄ nanoparticles. These tailored photocatalysts were evaluated for malachite green (MG) degradation in a Vis-light/CdFe₂O₄/H₂O₂ system, exhibiting pseudo-first-order kinetics with apparent rate constants enhanced by up to 31-fold as a function of solution pH. MG degradation proceeded via reactive oxygen species (ROS), including h⁺, ^·OH, and O₂⁻^·, with h⁺ identified as the dominant oxidative species. The system showed strong pH responsiveness and sensitivity to inorganic salts ions, attributable to fuel-dependent adjustments in surface charge and morphology. Furthermore, the CdFe₂O₄ displayed excellent stability, retaining high photocatalytic activity over nine consecutive reuse cycles.</p> Graphical Abstract <p></p>