You are right, this is difficult in one step, but
CO disproportionates already at relatively low temperatures into C and CO2, although this requires some catalysator, as CO is thermodynamically unstable with respect to this disproportionation already at normal temperature. Hence generation of C is the trivial part. On the other hand, CO2 disproportionates at higher temperatures into CO and O2. Taken together this seems to me a perfectly viable cycle to decompose CO into C and O2.