Via nanotube technology:
The nanotubes are arranged vertically, almost like empty honeycomb. Over the top of the nanotubes sits a thin, reddish-brown layer of copper oxide. Both the copper and titanium oxide act as catalysts, speeding up reactions that take place naturally.Interesting.
When sunlight hits the copper oxide, carbon dioxide is converted into carbon monoxide. When sunlight hits the titanium oxide, water molecules split apart. The hydrogen freed from the water and the carbon freed from CO2 then recombine to create burnable methane, and the spare oxygen atoms pair up to create breathable oxygen.