NH2-UIO-66 Based Hydrophobic Porous Liquid with High Mass Transfer and Affinity Surface for Enhancing CO2 Photoreduction

Abstract

Increasing the CO₂ concentration on the surface of the photocatalysts helps to increase the reaction dynamic rate of the photocatalytic CO₂ reduction. However, the low solubility and poor mass transfer of CO₂ in aqueous phase seriously hinder the adsorption and conversion of CO₂ at the active site. In this work, the porous liquid photocatalyst (NH₂-UIO-66 PL) with strong hydrophobicity has been synthesized by grafting the hydrophobic liquid end long-chain (PDMS) onto the amino site of metal-organic framework (NH₂-UIO-66). It is found that the NH₂-UIO-66 PL with permanent porosity causes a large amount of CO₂ to be concentrated in the porous liquid cavity for transporting and diffusing CO₂ onto the photocatalyst surface rapidly, and then the CO₂ affinity surface with high positive potential and key intermediates for activation reduction reactions are formed with the grafting of hydrophobic PDMS, leading to stronger electron enrichment Zr active sites for enhancement of the overall CO₂ reduction ability. As a result, NH₂-UIO-66 PL achieved CO₂ photoreduction with a CO yield of 24.70 μmol∙g⁻¹∙h⁻¹ and CH₄ yield of 7.93 μmol∙g⁻¹∙h⁻¹, which is 2.3-fold and 2.7-fold compared to hydrophilic NH₂-UIO-66, respectively. This research provides a novel design of hydrophobic porous liquids to provide industrial possibilities for high CO₂ adsorption and reduction.

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