Search

The development of efficient, cost-effective and heterogeneous catalysts for the valorization of CO2to high-value chemicals is of vital importance in reducing CO2emissions. 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)2and 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 CO2and 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−1compared 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. more...

Developing highly efficient, cost-effective and robust heterogeneous catalysts for carbon dioxide (CO2) fixation into valuable chemicals plays an essential role in carbon emissions reduction. Herein, a family of novel and bifunctional hypercrosslinked polymers, which consist of amide groups (-CONH-) as hydrogen bond donors (HBDs) and Br¯ as nucleophiles, were developed for metal- and co-catalyst free cycloaddition of CO2to epoxides. The incorporation of amide units into the polymeric networks not only provided active sites for synergistic activation of epoxides, but it also enhanced their swelling abilities toward epoxide substrates. As a result, the optimal catalyst exhibited high catalytic performance towards the cycloaddition of CO2and epoxide to cyclic carbonate, the catalytic activity was comparable to those of the homogeneous analogues and outperformed most of the metal-free polymeric catalysts previously reported. Experimental and density functional theory (DFT) investigations suggested that excellent activity of the catalyst stemmed from the synergistic effect between amide HBDs and Br¯ nucleophiles, as well as its excellent swelling ability toward epoxides. Additionally, the catalyst exhibited excellent structural stability and could be reused at least 10 times without significant activity loss. The present work not only highlights a versatile HBD to construct efficient and robust solid catalysts for CO2fixation, but also paves the way to boost the performance of polymeric catalysts by engineering their swelling abilities toward reactant molecules. more...