Use of metal-organics based solvents for CO₂ capture

There are a number of metal-organic compounds that can loosely be considered CA mimics and which are known to absorb CO₂ directly from the atmosphere. The metal-organic complex, {Zn[N[CH2(2-py)]3](μ-OH)}2(NO3)2 (I), is one such complex. In the present study, the sorption of CO₂ by water solutions of complex I have been studied by NMR (using D2O as solvent and absorbing 99.9% 13C enriched CO₂) and vapor-liquid equilibria measurements to understand the mechanisms of sorption when using such complexes. The potential of I/water solvents for use in CO₂ capture has been evaluated by comparison with mono- ethanolamine (MEA)/water solvents. The metal-organic solvent shows higher sorption capacity than MEA on a molar basis; also, three cycle tests indicate that I/water solvents can be regenerated efficiently at low temperatures giving a potential significant

reduction in regeneration energy requirements as compared to MEA/water solvents. On the other hand, due to its more than 14 times lower molar mass, MEA solvents have higher CO₂ sorption capacities on a kg solvent basis. The two solvents show similar sorption kinetics.