Al-MOF CAU-10 for Sorption-Enhanced CO₂-to-Methanol Reaction: Role of the Hydrophilic/Hydrophobic Balance

In this study, we conducted a comprehensive investigation relating to the efficiency of the Al-MOF CAU-10 as a sorbent in a Sorption Enhanced Reaction Process (SERP) based on its hydrophilic/hydrophobic balance. We confirmed both experimentally and through simulation that CAU-10 is a hydrophobic material at low pressure, whereas it shows a high affinity for methanol. The cosorption of water and methanol shows that both molecules are in competition, mostly for the oxygen atoms of the ligands. An important result is the influence of the relative pressure of the vapor mixture on the composition of the adsorbed phase. At low relative pressure, methanol is mostly adsorbed from the mixture, while water is only adsorbed from 0.16 p/p°. At higher relative pressures, water becomes predominant in the adsorbed phase. We therefore took advantage of this result to improve the catalytic reduction of CO₂ into methanol by sorption of methanol or water. The catalytic test was performed at 270 °C under a total pressure of 50 bar. Under these conditions, the methanol yield increased by more than 6% compared to a catalytic reaction performed without sorbent, thus validating our fundamental approach.