To the best of our knowledge, CO 2 fractions lower than 5 mol % have so far only been achieved by Chazallon and Pirim who were capturing minute amounts of CO 2 from a 1 mol% feed gas in their in-situ Raman cell. Due to their use of liquid water, which translated to a formation temperature of roughly 271 K, more than 140 bar of pressure had to be applied for capture. This is in strong contrast to the pressure requirements shown in Fig. , highlighting the leverage gained when transitioning to sub-zero Celsius. For instance, to obtain a CO 2 fraction of less than 10 mol% in the product gas a pressure of at least 35 bar and 13 bar is required for a temperature of 253 K and 233 K, respectively. Hence, by simply reducing the temperature by 20 K, the pressure can be reduced by more than half. This massive reduction in equilibrium pressure is evidently even more pronounced when comparing with HBCC from liquid water, where more than 100 bar are required for a similar product gas concentration . Further, at 233 K, the unpromoted system's equilibrium pressures are even comparable to those of the same system at 274 K when promoted with the well-known and efficient thermodynamic promoter tetrahydrofuran (THF) . As the attainment of CO 2 -lean product gas at minimal pressure and related energy input is highly desirable from an economic point of view, the low-temperature route of HBCC is tempting at first sight. However, the slower formation kinetics associated with lower temperatures and mass transfer limitations are drawbacks that have so far prevented a broader consideration of this path for HBCC. Therefore, to ensure viability of HBCC at such process conditions, kinetics must be promoted. In the following section, it is investigated whether the combined effect of the high surface area of the packed bed of solidified dry water and the promoting abilities of silica are sufficient for enhancing rates of formation to a degree viable for the industrial application.