The complexes of formic acid (HCOOH, FA) with carbon dioxide are studied by infrared spectroscopy in an argon matrix. Two trans-FA center dot center dot center dot CO2 and one cis-FA center dot center dot center dot CO2 complexes are experimentally identified while the calculations at the MP2(full)/6-311++G(2d,2p) level of theory predict one more minimum for the cis-FA center dot center dot center dot CO2 complex. The complex of the higher-energy conformer cis-FA with CO2 is prepared by vibrational excitation of the ground-state trans-FA conformer combined with thermal annealing. The lifetime of the cis-FA center dot center dot center dot CO2 complex in an argon matrix at 10 K is 2 orders of magnitude longer than that of the cis-FA monomer. This big difference is explained by the computational results which show a higher stabilization barrier for the complex. The solvation effects in solid argon are theoretically estimated and their contribution to the stabilization barriers of the higher-energy species is discussed. The relative barrier transmissions for hydrogen tunneling in the cis-FA center dot center dot center dot CO2 complex and cis-FA monomer are in good agreement with the experimental decay rates.