A system, sorbent formulations, methods of preparation, and methods are described that provide selective sorption and release of CO.sub.2 from CO.sub.2-containing gases such as syngas. The sorbent may include magnesium oxide (MgO) and a group-I alkali metal nitrate. The sorbent may also include a group-I alkali metal carbonate and/or a group-II alkaline-earth metal carbonate.
STATEMENT REGARDING RIGHTS TO INVENTION MADE UNDER FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
 This invention was made with Government support under Contract DE-AC05-76RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.