Single-atom Zn on bipyridine-functionalized porous organic polymers towards highly efficient N-formylation of amines with CO2 under mild conditions

Abstract

The development of efficient, cost-effective and heterogeneous catalysts for the valorization of CO2 to high-value chemicals is of vital importance in reducing CO2 emissions. Herein, single-atom Zn on bipyridine-based porous organic polymer was successfully fabricated through a facile copolymerization of divinyl-bipyridine and divinyl-benzene monomers, followed by complexation with Zn(OAc)2. The prepared materials with different concentrations of bipyridine moieties possessed large surface areas, hierarchical porosity, and strong coordination interaction between Zn(OAc)2 and the polymer scaffold. Catalytic evaluation demonstrated that the optimal single-atom Zn catalyst displayed extremely high catalytic performance towards the N-formylation of amines with CO2 and PhSiH3. Notably, under mild reaction conditions (30 °C, 1 bar CO2), a Zn loading as low as 0.5 mol‰ was sufficient for 94% yield of N-methylformanilide, with a record-high turnover frequency (TOF) of 376 h−1 compared to previously reported heterogeneous catalysts. Moreover, the solid catalyst could be easily recovered and reused for five cycles. Additionally, various amines could be efficiently transformed into corresponding formamide with moderate to high yields. The present work highlights a facile and cost-effective method for constructing highly efficient and recyclable single-atom metal catalysts for N-formylation of amines with CO2.