Figure 4. Influence of temperature on the hydrogenation of CO₂ to formic acid using [RuCl₂(PTA)₄] as the catalyst: 90 °C (brown circle), 60 °C (red diamond), 50 °C (blue square), 40 °C (green asterisk) and 30 °C (pink triangle).

Conditions: [RuCl₂(PTA)₄] was dissolved in H₂O (2.76 mM, 2 ml), under N₂ atmosphere. The solution was pressurized at room temperature with CO₂ (50 bar) and completed with H₂ to 100 bar. The system was heated to the desired temperature and the reaction was monitored by ¹H NMR spectroscopy until the equilibrium of the reaction was reached. The values are averaged from three to six measurements with a reproducibility of ±15%.