Evaluating the performance and suitability of MIL-91(Ti) MOF for post-combustion carbon capture by vacuum pressure swing adsorption (VPSA)

A multiscale study was carried out to evaluate MIL-91 (Ti) sorbent for post-combustion CO2 capture in industrially relevant conditions. Initially, the process performance of the MOF was assessed using molecular simulated adsorption isotherms, which predicted an energy consumption of 1.65 MJ/kg and a productivity value of 0.42 mol/m³ ads s. Subsequently, MIL-91 (Ti) was characterized using several complementary experimental techniques, and the characterization data were supplied to a process simulator to assess energy consumption and productivity values for 95% purity and 90% recovery targets. The experimental adsorption isotherms resulted even better process performance, with a minimum energy consumption of 1.03 MJ/kg, and a maximum productivity of 0.61 mol/m3 ads s, compared to the GCMC simulated adsorption isotherms. This discrepancy can be attributed to the use generic force filed in the molecular simulation, which cannot accurately capture host-guest intermolecular interactions with the MOF pore surface in a highly confined environment of MOFs like MIL-91. However, the lower energy consumption and higher productivity of actual MIL-91 (Ti), which are both desirable outcomes for CO2 capture processes, suggests the viability of MIL-91 (Ti) for the implications in real CCS applications.