By far the most credible case for asteroid mining is water & carbon compounds. A little H, O, and C, and you have conventional hydrocarbon propellant + LOX.
I don't know what the actual claim that is being made here is; This seems to redirect ultimately to a lay press release from a state space agency rather than to a scientific paper. There do seem to be a number of competing articles on electrochemical synthesis of ethylene from CO2.