Facile preparation of CuO-Gd2Ti2O7 using Acmella uliginosa leaf extract for photocatalytic degradation of malachite green

•CuO-Gd2Ti2O7 has been successfully prepared by a two-phase system of hexane-water.•Optical bandgap of Gd2Ti2O7 decreased from 3.68 to 1.78 eV after decoration with CuO.•Gd2Ti2O7 actively work in the visible region.•CuO-Gd2Ti2O7 exhibited the highest photocatalytic activity for MG degradation. CuO-Gd2Ti2O7 has been prepared in a two-phase system of polar precursor solution and non-polar hexane fraction of Acmella uliginosa leaf extract (AUE). The secondary metabolites in AUE have an essential role in the synthesis of CuO-Gd2Ti2O7. The optical bandgap value for CuO-Gd2Ti2O7 plummeted from 3.68 to 1.78 eV, compared to Gd2Ti2O7. The photocatalytic activity was investigated to degrade malachite green (MG) under visible light illumination. As a result, CuO-Gd2Ti2O7 showed the MG degradation percentage of 88.60% after 90 min of illumination, which was 1.9 times higher than the MG degradation percentage over Gd2Ti2O7. The improved photocatalytic activity could be ascribed to the narrower optical bandgap Gd2Ti2O7 after being decorated by CuO, which effectively works in the visible region. This research suggests a novel method to prepare CuO-Gd2Ti2O7 as a promising candidate with good photocatalytic activity for the degradation of malachite green under visible light illumination. [Display omitted]