Synergism of carbon nanotubes and porous-organic polymers (POPs) in CO2 fixation: One-pot approach for bottom-up assembly of tunable heterogeneous catalyst

A porous-organic polymer (POP) was constructed through bottom-up assembly from its molecular precursors atop multi-walled carbon nanotubes (MWCNTs) in a one-pot synthesis, affording a composite material POP@MWCNTs. The composite was found to be microporous and with pronounced affinity towards gaseous CO2 (heat of adsorption of ∼45 kJ/mol at initial coverage). The composite was characterized through several techniques including gas sorption, FTIR spectroscopy, SEM, AFM, and TEM microscopy, elemental analysis and thermogravimetric (TGA) analyses. The homogenous coating of the POP on top of the MWCNTs was evident from its electron microscopy images. Quantum mechanical calculations for geometry optimization of a fragment of the polymer and of the composite indicated rigidified structure of the POP in contact with the MWCNTs, further supporting and explaining the findings from the gas sorption measurements conducted herein. In Addition, the composite was found to be electrochemically active towards CO2 reduction, surpassing the properties of either of its two components, indicating enhanced interfacial interactions between the MWCNTs and the POP. Moreover, the catalytic behavior of the composite was straightforwardly enhanced through post-synthetic incipient wetness impregnation of Cu(I) ions, demonstrating tunnability of the catalyst. This approach delineates a pathway to merge the properties of both families of materials, on the molecular level, aiming to extend the realms of microporous solids into electrocatalytic CO2 capture and sequestration technologies.

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