The tail of imidazole regulated the assembly of two robust sandwich-type polyoxotungstate-based open frameworks with efficient visible-white-light-driven catalytic oxidation of sulfides

Abstract

Visible-white-light-driven selective aerobic oxidation of sulfides is highly attractive but challenging for modern organic and pharmaceutical synthesis. Thus, there is an urgent need for exploiting high-performance photocatalytic systems to reform the value-added organic transformation. Herein, we elucidated a bottom-up strategy to construct two robust zinc-imidazole metal–organic linker extended sandwiched-type polyoxotungstate-based open frameworks (POTOFs), {[Zn(1-pIM)₃]₂[Zn₆(AsW₉O₃₃)₂(1-pIM)₆]·2(1-HpIM)·2H₂O}_n (LCU-20) and {[Zn(1-ipIM)₃]₂[Zn₆(SbW₉O₃₃)₂(1-ipIM)₆]·2(1-HipIM)}_n (LCU-21) (1-pIM = 1-propylimidazole, 1-ipIM = 1-isopropylimidazole) by tuning the substituent tails outside the imidazole. Interestingly, LCU-20 and LCU-21 exhibit 2D sql and 3D 2-fold interpenetrated lvt networks, respectively, although both nodes in LCU-20 and LCU-21 are similar 4-connected Zn₆ ring seamed trivacant polyoxotungstate anions. Interestingly, the substituent tails of imidazole instead of the heteroatom in polyoxotungstates play a key role in determining the network propagation orientation that dictates the dimensionality of the final network of POTOFs. More importantly, the alliance of sandwich-type polyanions and zinc-imidazole metal–organic units can produce metal-to-metal charge transfer (MMCT) chromophores, endowing them with visible-light responsive features. Therefore, benefiting from the oxidative active species of O₂˙⁻ and h⁺, LCU-20 exhibits efficient heterogeneous catalytic activities for the oxidation of sulfides with high yield (∼99%) and excellent selectivity (∼99%) under visible-white-light irradiation (>600 nm) in the ambient environment. This work not only presents a new approach for the construction of 3D POTOFs but also describes the white-light-driven oxidation of sulfides catalyzed by this type of material.