When CaO absorbs CO2 in pre-combustion systems, it can greatly increase the H2 yield from pyrolysis and gasification reactions. However, natural sources of CaO, such as limestone (CaCO3), produce sorbents that quickly lose reactivity, and more stable sorbents are therefore desired. Although both synthetic and biopolymers can induce the formation of a wide variety of CaCO3 morphologies, only a few synthetic polymers and perhaps no natural polymers have been applied to the synthesis of CO2 sorbents. We prepared CaO precursors templated on three natural polysaccharides (chitosan, agar, and carrageenan) and three synthetic polymers [poly(acrylic acid), poly(ethylene glycol), and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide)] and tested these as CO2 sorbents. The sorbents templated on biopolymer films had interesting reactivity that was affected by residual biopolymer, even after several calcination–carbonation cycles at high temperatures. However, these sorbents were not more effective than CaO deri...