Rational Design of Synergistic Structure Between Single-Atoms and Nanoparticles for CO2 Hydrogenation to Formate Under Ambient Conditions

Single-atom catalysts (SACs) as the new frontier in heterogeneous catalysis have attracted increasing attention. However, the rational design of SACs with high catalytic activities for specified reactions still remains challenging. Herein, we report the rational design of a Pd1-PdNPs synergistic structure on 2,6-pyridinedicarbonitrile-derived covalent triazine framework (CTF) as an efficient active site for CO2 hydrogenation to formate under ambient conditions. Compared with the catalysts mainly comprising Pd1 and PdNPs, this hybrid catalyst presented significantly improved catalytic activity. By regulating the ratio of Pd1 to PdNPs, we obtained the optimal catalytic activity with a formate formation rate of 3.66 molHCOOM·molPd−1·h−1 under ambient conditions (30°C, 0.1 MPa). Moreover, as a heterogeneous catalyst, this hybrid catalyst is easily recovered and exhibits about a 20% decrease in the catalytic activity after five cycles. These findings are significant in elucidating new rational design principles for CO2 hydrogenation catalysts with superior activity and may open up the possibilities of converting CO2 under ambient conditions

Ambient Conversion of Carbon Dioxide into Liquid Fuel by a Heterogeneous Synergetic Dual Single-Atom Catalyst

Ambient conversion of carbon dioxide into various liquid fuels or chemicals is a potential economical solution for reducing CO2 emissions, which may be responsible for recent climate change. Here, we report a highly active dual single-Pd-atom catalyst for ambient conversion of CO2 to formic acid using a step-by-step catalyst design strategy by the density functional theory (DFT) method. The theoretically predicted catalyst is synthesized experimentally and verified to capture a significant amount of CO2 (5.05 mmol/g, 273 K), and it can efficiently convert CO2 to formic acid under ambient conditions (30 °C, 1 bar) with a turnover frequency (TOF) as high as 13.46 h-1, which is the first such report in the field of heterogeneous catalysts. Two major factors contributing to this extraordinary catalytic activity include a pore enrichment effect of the microporous structures of the covalent triazine framework and a ternary synergetic effect among two neighbouring Pd atoms and rich nitrogen environment. Our work may aid the development of heterogeneous catalysts to produce other commonly used fuels from CO2 under ambient conditions

Liquid Sunshine: Formic Acid

“Liquid sunshine” is the conceptual green liquid fuel that is produced by a combination of solar energy, CO2, and H2O. Alcohols are commonly regarded as the preferred candidates for liquid sunshine because of their advantages of high energy density and extensive industrial applications. However, both the alcohol synthesis and H2 release processes require harsh reaction conditions, resulting in large external energy input. Unlike alcohols, the synthesis and dehydrogenation of formic acid (FA)/formate can be performed under mild conditions. Herein, we propose liquid sunshine FA/formate as a promising supplement to alcohol. First, we outline the vision of using FA/formate as liquid sunshine and discuss its feasibility. Then, we concentrate on the application of FA/formate as liquid organic hydrogen carrier and summarize the recent developments of CO2 hydrogenation to FA/formate and FA/formate dehydrogenation under mild conditions. Finally, we discuss the current applications, challenges, and opportunities surrounding the use of FA/formate as liquid sunshine