I agree with the authors on the enormous importance that direct air capture technologies will have in climate change mitigation, either to remove CO₂ from the atmosphere (and then store it underground) or to use that atmospheric CO₂ in the synthesis of truly 100% renewable fuels (i.e. made with 100% renewable energy and CO₂ ). The technologies are much closer than people think and there are no major chemical or physical barriers to developing them. The debate is about which will be the cheapest and whether we will be able to afford the price. I am optimistic about all this: there are more than 100 start-ups already created and a lot of science and engineering under development that will bear fruit and make news in a few years.

However, I think this article is of mediocre quality. I am surprised by its publication in Nature. I would like to assume that its scientific value lies in its proposal of new methods of organic synthesis that produce materials with properties of some interest to experts in that field (not mine and I cannot assess whether that is the case). But as functional materials for CO₂ capture they are very, very far from demonstrating their capabilities on a large scale.

The reason is simple: any CO₂ capture system (captured from air or any other gas) aims to generate a highly concentrated stream of CO₂ in the regeneration stage. The authors say virtually nothing about how such an almost pure_CO2 stream is to be obtained. Everything revolves around the measurements in the adsorption stage, but their regeneration stages are performed by diluting the adsorbed CO₂ with N₂, and I have not found what the CO₂ concentration is at the outlet of the solids bed in that regeneration stage at only 60 ºC (very low, I am afraid).

The stability of the material, which in practice requires hundreds of thousands of adsorption-desorption cycles, is also not demonstrated by its few multi-cycle tests. Moreover, this stability will be affected by the regeneration conditions (surely at higher temperature? Or with steam?) necessary to obtain high CO₂ concentrations during regeneration. I am really surprised that this is published in Nature.