Enhancement of formic acid production from carbon dioxide hydrogenation using metal-organic frameworks: Monte Carlo simulation study

Formic acid production from CO2 allows the reduction of carbon dioxide emissions while synthesizing a product with a wide range of applications. CO2 hydrogenation is challenging due to the cost of transition metal catalysts and the toxicity of the transition elements. In this work, the thermodynamic confinement effects of the metal-organic framework UiO-66 on the CO2 hydrogenation to formic acid were studied by force field-based molecular simulations. The confinement effects of UiO-66 and the metal-organic frameworks Cu-BTC, and IRMOF-1 were compared, to assess the impact of different pore size and metal centers on the production of HCOOH. Monte Carlo simulations in the grand-canonical ensemble were performed in the frameworks, using gas phase mole fractions of CO2, H2, and HCOOH at chemical equilibrium, obtained from Continuous Fractional Component Monte Carlo simulations in the Reaction Ensemble. The adsorption isobars of the components in metal-organic frameworks were computed at 298.15 - 800 K, 1 - 60 bar. The enhancement of HCOOH production due to preferential adsorption of HCOOH in metal-organic frameworks was calculated for all studied conditions. UiO-66, Cu-BTC, and IRMOF-1 affect CO2 hydrogenation reaction, shifting the thermodynamical equilibrium toward HCOOH formation. The prevailing factor is the type of metal center in the metal-organic framework. The confinement effect of Cu-BTC turns out to exceed the enhancement caused by UiO-66, and IRMOF-1. The resulting mole fraction of HCOOH increased by ca. 2000 times compared to the gas phase at 298.15 K, 60 bar. Cu-BTC can be considered as an alternative to improve the production of HCOOH due to elimination of the high-cost temperature elevation, cost reduction of downstream processing methods, and comparable final concentration of HCOOH to the reported concentrations of formate obtained using transition metal catalysts.

Automated summary

Formic acid production from CO2 can reduce carbon dioxide emissions while synthesizing a versatile product. This study investigated the confinement effects of metal-organic frameworks on CO2 hydrogenation to formic acid through molecular simulations. The results showed that metal-organic frameworks, such as UiO-66, can enhance the production of formic acid by shifting the thermodynamic equilibrium.