It's curious that you didn't actually include the calculation of what the minimum energy requirement; instead, you just assert without evidence that it is "very, very, very high".

In fact this theoretical minimum is not very high; as https://en.wikipedia.org/wiki/Direct_air_capture#Environment... explains, it is only 250 kWh/tonne CO₂, or 900 kJ/kg in SI units. To remove the ≈60 Gt/year of anthropogenic CO₂ currently being emitted and get us to carbon-neutral with direct air capture would consequently require a theoretical minimum of 1.7 terawatts, which is only about 10% of current world marketed energy consumption, and presumably about 5% of world marketed energy consumption 10 years from now. Kicking climate change into reverse would require a bit more than that, maybe double. Depending on the sorbent system, this energy can be solar thermal; it does not have to be electrical.

Existing direct air capture systems like Climeworks's do not closely approach the theoretical minimum. Do you know how much energy they require?

Point source capture is of course much cheaper but it cannot get us to net negative CO₂ emissions.