Enhancement of visible-light-driven oxidative amine coupling under aerobic and anaerobic conditions by photocatalyst with spatial separation of photoinduced charge carriers

Spatial separation of oxidation/reduction cocatalyst is an effective means to improve the efficiency of charge separation in photocatalytic reaction systems.Herein,a yolk-shell Pd@NH_(2)-UiO-66@Cu_(2)O heterojunction was designed and synthesized by integration of electron collector Pd and hole collector Cu_(2)O inside and outside of a photoactive metal-organic framework(MOF)NH_(2)-UiO-66,respectively.The obtained Pd@NH_(2)-UiO-66@Cu_(2)O heterojunction effectively inhibits the electron and hole recombination through the photo-induced electrons and holes flow inward and outward of the composite,and promotes the reduction and oxidation abilities for the oxidative coupling of benzylamine to imines.Compared with Pd/NH_(2)-UiO-66@Cu_(2)O,Pd@NH_(2)-UiO-66,and Pd/NH_(2)-UiO-66,Pd@NH_(2)-UiO-66@Cu_(2)O exhibits the highest photocatalytic activity.More importantly,Pd@NH_(2)-UiO-66@Cu_(2)O shows a conversion rate of benzylamine up to 99%either by oxidation under aerobic conditions or by strong adsorption of H atom(Hads)under anaerobic conditions.In addition,the catalyst shows good stability and can be recycled at least ten times.This work provides useful guidance on construction of MOFs-based composites with spatially separated photoinduced charge carriers to realize efficient oxidation coupling of benzylamine in both aerobic and anaerobic conditions.