Construction of a stable porous composite with tunable graphene oxide in Ce-based-MOFs for enhanced solar-photocatalytic degradation of sulfamethoxazole in water

Pharmaceutically active compounds (PhACs) are ubiquitously detected in water matrices, arousing growing concern. Effective abatement of these toxic environmental contaminants is challenging but of great importance. Ce-based MOFs have been considered novel metal–organic framework (MOFs)-based photocatalysts in water treatment. However, limited light absorption ability, fast recombination of photogenerated carriers, and water stability limited the further application. Here, the UiO-66 (Ce) was successfully constructed onto the surface of a series of graphene oxide (GO) (1 mg ∼ 7.5 mg) in situ. GO with oxygen-containing functional groups (OCFGs) increased the adsorption (∼45 %) of the trace amount of sulfamethoxazole (SMX) (200 μg/L) over the interfaces and enhanced the degradation efficiency of SMX. The composite with the optimal ratio (GO@ UiO-66 (Ce)-5) significantly increased the charge separation ability and produced a large number of reactive oxygen species (ROS). •O₂^– was proved to be the major driving reactive substance for SMX degradation with the calculated steady-state concentration of 2.5 × 10^-9 M (∼1.37 times higher with bubbled oxygen), which is much higher than that of detected •OH (1.62 × 10^-14). Major operational parameters including dissolved oxygen, initial solution pH, and catalyst dosages were investigated systematically. Several intermediates were identified by high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (HPLC-MS/MS). By choosing the strategy, MOFs were closely bonded to the surface of the GO matrix, making the leakage of Ce ions inhibited obviously (∼3 times) in the water treatment process. This study offers useful guidance for improving the performance of existing photocatalytic materials for PhACs removal.