Re ISS, I've been clicking around on this a bit more, and
> While cabin air processing, one carbon dioxide removal bed is in the process of regeneration. Regeneration is accomplished using pressure/thermal swing methodology. First, the two-stage pump removes the free air from the adsorbent bed and returns it to the cabin, reducing oxygen ullage. Then Kapton heaters integrated within the adsorbent bed raise the zeolite temperature, and space vacuum creates a low, partial pressure driving the carbon dioxide gas overboard. Daylight and continuous day power cycle is overlapped with the operating cycle. In the daylight power cycle, the carbon dioxide adsorbent bed heaters are only allowed to be powered on during the day portion of the cycle
> [...]
> The CDRA continuously removes 6 person-equivalents of CO, when operating with both C02 removal beds (dual beds) functioning.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/200502...
Converting CO2 into CO would be rather counterproductive (absent a reliable and efficient mechanism to remove CO), I suspect an efficient setup will involve "mechanical" filtration not chemical reactions.
