It’s always some designer behance thing for these air moisture harvesters. Here’s the material they talk about https://onlinelibrary.wiley.com/doi/epdf/10.1002/smll.202304562. Which shows a harvesting efficiency of about 0.2 g/g so you need 5x as much MOF as you want water in the end, so a liter of water per cycle requires 5 kg of MOF (not sure how the efficiency scales with increasing amounts, might be less efficient). The other issue is that if you want a liter of water, you need a LOT of air in that little chamber. 50%humidity at 30 C holds 15 grams of water per cubic meter, so 1 liter of water requires 66 cubic meters of air, or about the size of a 5mx5m room.

Additionally, to be fully passive, this machine can only be cycled once per day. So the most realistic version of this looks more like: a large, heavy container of MOF, multiple kilograms, spread out like hvac filter to maximize airflow, sits out all night when the humidity spikes, loads up on water. Then in the morning the mof is sealed into a box with a solar collector to heat the box, and water leaves the mof and condenses somewhere cooler.

Maybe a better version is lightly powered by a solar panel, and has like 4+ smaller mofs that it rotates into the sun to extract for an hour, then into the shade to absorb more, and there’s always one absorbing in the shade, and one sweating in the sun, but that will cut the efficiency of the MOF significantly since the temperature and humidity are not as good for absorption during the day.

All in all, I wish people would stop posting water harvesters. Water insecurity is not really a problem of “no water exists in this environment so I have to take it from the air” but rather a water management and infrastructure problem. And there are quite few places that experiences regular extremely high humidity, but no standing or running water.