The present invention provides a system for the capture and purification CO.sub.2 and a purification unit for said system, wherein said purification unit comprises: a first filter having a first container and a first filler material; a second filter having a second container and a second filler material, downstream of said first filter; a third filter having a third container and a third filler material, downstream of said second filter, said third filter having, additionally, a heating element thermally coupled to said third filler material; and control means of said heating element; wherein said first filler material is silica; wherein said second filler material is zeolite; and wherein said third filler material is a metal-organic framework modified with activated carbon.