Can a solvent be a gas?
Solvents imply dissolving process as intermolecular interactions between solvent and solute, leading to disperging the solute from the condensed form.

"Permanent" gases near normal conditions do not provide such interactions. Volatile compounds evaporate with or without presence of gas. Gas is rather a bystander/spectator of such evaporation.

Fluids near critical conditions like supercritical CO2 share many properties of liquids and gases, so such interactions are present, so in some sense and with both eyes closed, one can consider it as solvent and gas.