I have no idea if something like that could work to be honest. Does the water absorb carbon from the air or just things like dust particles.

Why not just plant more trees? They clean the air as well... I have (a beginning and tiny) agroforest, if we drastically switch away from our current agriculture model to large scale agroforestry we create more jobs, clean the air and safeguard humanity's food supply.

I read somewhere that planting 40 trees offsets a person's carbon footprint, I have no idea if this is true and what the calculation is based on but if it is true I have planted enough so far to offset the carbon footprint of my entire family already..imagine if we would be required to plant 40+ trees a person during our lifetime, the world would be a beautiful place ^^

There are some plants, they were mentioned in a TED talk (can't remember by who), that have a measurable effect on air quality, they are a lot smaller than trees (I believe they could be waist or shoulder high).

There is an added psychological benefit of having plants in your environment. I understand we have costs and availability of space to consider when setting up a space station but if you consider the current cost of mental health here on the planet, taking into account the long-term mental health of whoever we send up there might be well worth it.

I'm sure there is a way to make it cost efficient if you consider that plants could have a variety of simultaneous functions, oxygen, food, mental health and other.

Which would mean spending time with a headset on just to get the benefit plants can give while doing other things ^^

And it would still leave food as a reason to have plants...

Personally I can't imagine AR will give me the same feeling as being surrounded by plants, I moved away from the city to a small farm, being surrounded by green, being able to just grab a fruit from a tree and eat it is one of the things I enjoy most in life :)