Pin it to a carbon atom.

Where’s the carbon going to come from? If it’s anywhere but the CO2 in the atmosphere (or at least sequestered on its way to the atmosphere), your energy solution isn’t carbon neutral anymore. And if it is from the atmosphere, then there are efficiency challenges there at concentrating CO2 to be useful for synthetic processes.

Most syngas today comes from biological and fossil feedstocks, so it’s not really a solution to atmospheric CO2 concentrations.