What flow rates can this achieve and sustain? If you want to use it for absorption of gasses or heat, presumably you are going to want to move that heat and gas

What flow rates can this achieve and sustain? If you want to use it for absorption of gasses or heat, presumably you are going to want to move that heat and gas somewhere. Diffusion is quite slow, so I expect you would need flowing water. It might not be all that valuable to have that surface area if you can't also move the water around. I imagine you could have many of these cubes with water flowing past one of their faces. Essentially using Diffusion to move stuff 1mm and using flow once the water is in a real pipe.