Continuous production of pure formic acid solution from CO2 hydrogenation at room temperature via amine-functionalized PdMn nano-alloy

[Display omitted] •Continuous and base-additive free production of pure formic acid solution in fixed-bed reactors by CO2 hydrogenation.•A record turnover frequency for base-additive free CO2 hydrogenation to formic acid.•Ternary synergetic effects of amine-functionalized PdMn nano-alloy contribute to the extraordinary activity. CO2 hydrogenation into formic acid is of great significance to mitigate CO2 emission. However, conventional routes typically require the addition of unrecyclable bases to shift the reaction equilibrium by the formation of formate, which leads to complex subsequent separation and difficulty in continuous production of pure formic acid solution. Here we report a secondary amine-modified PdMn nanocatalyst for the continuous production of pure formic acid solution in fixed-bed reactors via CO2 hydrogenation. By optimizing fine structure of PdMn nano-alloy, the optimal TOF of up to 26.5 h−1 is obtained under mild reaction conditions (25 ℃, 3.0 MPa). This is one of the highest levels reported for a heterogeneous catalyst without alkali additives under similar conditions. The characterization shows that the two-component alloying effect of PdMn and the synergistic effect between PdMn NPs and secondary amine group (NH) are the key to obtaining superior reactivity. These findings in this work may pave an avenue for conversion of CO2 in a more environmentally friendly way.