New molecular basket sorbents for CO2 capture based on mesoporous sponge-like TUD-1

• Mesoporous TUD-1 materials are effective support of molecular basket sorbents for CO2 capture.
• Compared to PEI/SBA-15, the TUD-1 based MBS show a significantly higher volumetric capacity and faster CO2 sorption kinetics.
• Both the pore volume and pore size play a crucial role in determining the CO2 sorption capacity of the TUD-1 based MBS.
• Best PEI loading of 50 wt%, positive moisture effect and good regenerability of PEI/TUD-1 were established for CO2 capture.

In this work, a new class of mesoporous and sponge-like TUD-1 materials have been explored as the support matrix for immobilizing a functional polymer, polyethylenimine (PEI), to prepare molecular basket sorbents (MBS) for CO2 capture. The performance of TUD-1 based MBS has been evaluated in a fixed-bed flow system using a simulated flue gas. Effects of the pore properties, PEI loading amount and moisture on the sorption capacity were examined. Compared to the well-known SBA-15, the TUD-1 based nano-porous MBS showed not only a comparable gravimetric capacity (∼115 mg-CO2/g-sorb), but also a significantly higher volumetric capacity (as high as 68 mg-CO2/mL-sorb). Both the pore volume and pore size play a crucial role in determining the CO2 sorption capacity of the TUD-1 based MBS. Furthermore, the TUD-1 supported PEI samples exhibited faster CO2 sorption kinetics than SBA-15 based MBS, due likely to the improved CO2 diffusion constant which was estimated by Parabolic diffusion equation. The highest CO2 sorption capacity of 116 mg-CO2/g-sorb was obtained with PEI loading of 50 wt% at 75 °C under dry conditions, which was further enhanced to 130 mg-CO2/g-sorb in the presence of moisture (3 vol%). The PEI/TUD-1 sorbent was tested for 45 sorption–desorption cycles, showing a good regenerability and cyclic stability. Because of its high CO2 sorption performance and commercial availability of the support, the TUD-1 based MBS could be promising for cost-effective capture of CO2 from flue gas.

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