Engineering boron-imidazolate-based polyoxometalates for photooxidative C=C bond cleavage in aqueous media
Jiajia Wang, Zhaoyang Wu, Qun Li, Hanlei Zhang, Yang Liu, Gang Ji, Yalin Zhang, Qian‐Li Li, Junyu Ren, Qingde Zhang, Xianqiang Huang
Abstract
The direct cleavage of alkenes to access value-added carbonyls under solar-driven conditions in aqueous media presents a considerable challenge. Addressing this challenge requires the construction of effective visible-light-responsive catalysts. Herein, two boron-imidazolate-based Strandberg-type polyoxomolybdophosphate hybrids, Co(H<sub>2</sub>O)<sub>4</sub>[HP<sub>2</sub>Mo<sub>5</sub>O<sub>23</sub>]<sub>2</sub>[B(HIM)(IM)<sub>2</sub>]<sub>2</sub>[B(HIM)<sub>3</sub>]<sub>2</sub>·12H<sub>2</sub>O (<strong>1</strong>) and Zn(H<sub>2</sub>O)<sub>4</sub>[HP<sub>2</sub>Mo<sub>5</sub>O<sub>23</sub>]<sub>2</sub>[B(HIM)(H<sub>2</sub>IM)<sub>2</sub>]<sub>4</sub>·7H<sub>2</sub>O (<strong>2</strong>) (IM = imidazole), were synthesized using a hydrothermal method and were utilized as efficient photocatalysts for the aerobic oxidative C=C bond cleavage of alkenes under natural sunlight and aqueous phase conditions. The incorporation of boron imidazolate ligands broadened the visible-light absorption region of polyoxometalates, and electrochemical tests highlighted their potential as exceptional photocatalysts. Upon visible blue light irradiation and ambient O<sub>2</sub> pressure in aqueous media, compound <strong>1</strong> exhibited remarkable aerobic photocatalytic activity, efficiently cleaving alkenes to yield the corresponding ketones (yields up to 91%). Notably, its catalytic performance remained consistent after three recycling runs under ambient sunlight, highlighting its robust stability and practical applicability. Subsequent mechanistic investigations revealed the involvement of O<sub>2</sub><sup>•−</sup> species in the reaction, and a possible mechanism for the cleavage of the alkenes was proposed.