Cooperative TiO2 photocatalysis with TEMPO and N-hydroxysuccinimide for blue light-driven selective aerobic oxidation of amines.

TiO2 has been the focus of attention in semiconductor photocatalysis for several decades because it can potentially settle the grand energy and environmental issues with earth-abundant elements of Ti and O. However, because of its wide band gap, TiO2 can only collect UV light, hindering its practical applications under the illumination of sunlight. In view of this, an interesting phenomenon of light-driven adsorption of amines onto TiO2 to form a visible light-absorbing complex was adapted to assemble smart photocatalysis. The endurance of this complex was eminently refurbished by blue light-driven continuous adsorption of amines. This in turn promoted a vital selective chemical transformation, blue light-driven selective oxidation of amines into imines with atmospheric dioxygen (O2). More importantly, the inclusion of TEMPO and N-hydroxysuccinimide (NHS) into the smart photocatalytic system could cooperatively expedite the blue light-driven selective aerobic oxidation of amines into imines through dual independent reaction channels, resembling that of enzymatic catalysis. This work underscores the importance of manoeuvring multiple reaction channels by cooperative photocatalysis during selective chemical transformations.