It has to be endothermic. Otherwise you could run a coal plant and get net power while getting your carbon back. Second law says nope. Could still work of cour

It has to be endothermic. Otherwise you could run a coal plant and get net power while getting your carbon back. Second law says nope. Could still work of course if it used solar heat or surplus industrial heat. If it was low maintenance you could deploy in places like the Sahara. Lots of free heat there. Edit: gas on the other hand could in theory be burned without CO2. A lot of the net energy there is the hydrogens combining with oxygen to form H2O. You could use fuel cells for maximum conversion efficiency and then recover the carbon.