Flying MOFs: polyamine-containing fluidized MOF/SiO₂ hybrid materials for CO₂ capture from post-combustion flue gas

Solid-state synthesis ensures a high loading and well-dispersed growth of a large collection of metal-organic framework (MOF) nanostructures within a series of commercially available mesoporous silica. This approach provides a general, highly efficient, scalable, environmentally friendly, and inexpensive strategy for shaping MOFs into a fluidized form, thereby allowing their application in fluidized-bed reactors for diverse applications, such as CO₂ capture from post-combustion flue gas. A collection of polyamine-impregnated MOF/SiO₂ hybrid sorbents were evaluated for CO₂ capture under simulated flue gas conditions in a packed-bed reactor. Hybrid sorbents containing a moderate loading of (Zn)ZIF-8 are the most promising sorbents in terms of CO₂ adsorption capacity and long-term stability (up to 250 cycles in the presence of contaminants: SO₂, NO and H₂S) and were successfully prepared at the kilogram scale. These hybrid sorbents demonstrated excellent fluidizability and performance under the relevant process conditions in a visual fluidized-bed reactor. Moreover, a biochemically inspired strategy for covalently linking polyamines to MOF/SiO₂ through strong phosphine bonds has been first introduced in this work as a powerful and highly versatile post-synthesis modification for MOF chemistry, thus providing a novel alternative towards more stable CO₂ solid sorbents.