Its also true.
Co2 is a gas.
Water for instance; it exists here as ice, which can absorb heat and change state to water. It can absorb heat again and change state to a gas.
CO2 cannot do that because it is already a gas, and it is why CO2 is irrelevant in global warming. It cannot hold any more heat energy.
Regardless, that's not the way that even the warmers claim that greenhouse gases work. You're constructing a straw-man for the warmers to have fun with.