Figures show that CO2 adsorption kinetics or mass transfer is one of the most critical factors in a TVSA process and also highly important in an S-TVSA process, so we must focus efforts on optimising this. The strong effect of CO2 adsorption kinetics on productivity is perhaps one of the easiest to explain. Faster adsorption kinetics leads to a sharper breakthrough curve with a shorter adsorption time and faster cycle time. Meanwhile, depending on whether the desorption step is heat transfer limited or mass transfer limited, faster adsorption kinetics can also shorten the desorption step (which is only expected at very low values of the LDF constant). The adsorption kinetics also affects the specific electricity, again because of the LDF constant's impact on the breakthrough curve. Slower adsorption and a broader breakthrough curve cause more CO2 to be lost from the end of the column during the adsorption step, and hence more air is required to be forced through the column to recover the same amount of CO2. The impact of CO2 adsorption kinetics on the specific thermal energy in a TVSA process is complex. There are two contributors to the specific thermal energy: the total thermal energy input into the column per cycle, and the cycle CO2 working capacity. Firstly, although the LDF constant Email: jpy1@hw.ac.uk RCCS, Heriot-Watt University does impact the CO2 working capacity, it ranks relatively low compared to other parameters, as shown in the ESI Figure . So, the CO2 adsorption kinetics must be impacting the total thermal energy input into the column. The rate of thermal energy input is only dependent on the heating driving force (the temperature difference between the column and heating fluid), and the heat transfer coefficient.