TPPS supported on core-shell PMMA nanoparticles: The development of continuous-flow membrane-mediated electrocoagulation as a photocatalyst processing method in aqueous media

Herein, the successful utilization of core shell poly-methyl methacrylate nanoparticles (CS-PMMA NPs) as a valuable support for organocatalyst immobilization in aqueous medium is presented along with an unprecedented direct current-based electrochemical method for processing a water colloid of the resulting nano-supported catalyst. The NP coagulation procedure relied on various electrocoagulation techniques and it was achieved through water electrolysis occurring in a dialysis membrane immersed in the colloid. Mass recoveries of up to 95% w/w were obtained for the NPs within 1 h of electrolysis. This was optimized at a constant current of 90 mA or a constant potential of 24 V. The disclosed NP separation procedure was effectively exploited in a continuous-flow reaction/separation/recycle sequence involving the tetraphenylporphyrin tetrasulfonate (TPPS) organo-photocatalyst immobilized on CS-PMMA NPs (NP2s). After an optimization study aimed at maximizing the chemical efficiency of the entire synthetic and purification process, the nano-supported catalyst NP2 (0.05 mol%) efficiently promoted the photoexcitation of triplet oxygen to singlet oxygen for the selective and environmentally benign sulfoxidation of a model sulfide in an aqueous medium.