Mechanistic insight into the electron-donation effect of modified ZIF-8 on Ru for CO2 hydrogenation to formic acid

The electron-donating effect of supports on active metals has been reported to be beneficial to improve catalytic activity of heterogenized molecule catalysts for CO 2 hydrogenation to formic acid . However, this effect has not been discussed in depth from the perspective of reaction mechanism, especially for CO 2 activation with the combination of theoretical calculations. Herein, we report a catalyst prepared via anchoring RuCl 3 on a post-synthetic modified (PSM) zeolitic imidazolate framework-8 (ZIF-8) in which linkers 3-methyl-1,2,4-triazole (Mtz) with a surplus of uncoordinated N sites have been incorporated. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveal that uncoordinated N sites in linkers donate additional electron-density to Ru, resulting in the decrease of energy barrier of CO 2 activation. And the RuCl 3 @ZIF-8-Mtz(0.29) catalyst containing the most Mtz ligands displayed the highest catalytic performance for the CO 2 hydrogenation to formic acid as compared to RuCl 3 @ZIF-8-Mtz(0.15) and RuCl 3 @ZIF-8.