Cellulose nanocrystals as bridges to construct CNCs@ZIF-8 3D network with topological chirality for realizing efficient photocatalytic reduction of CO2

Chiral nanomaterials typically exhibit special optical activities, such as optical rotation and chiral photomechanics, and have enormous potential for applications in molecular chiral photocatalysis and other fields. In this work, cellulose nanocrystals (CNCs) were obtained from renewable and affordable bamboo resources through the steps of delignification, hemicellulose removal and acid digestion. Meanwhile, ZIF-8 materials with truncated rhombic dodecahedral structure were obtained by liquid-phase synthesis from Zn2+ coordinated with 2-methylimidazole (2-MiM). And then, the topologically chiral CNCs@ZIF-8 3D network was successfully constructed by using CNCs as a bridge to graft with ZIF-8 through the formation of Zn–N–S and Zn–O–S bonds. The photoreduction yield of CO2 to CO by CNCs@ZIF-8 (α = +21.290) with topological chirality was 301.16 μmol−1·g−1, which was 9.43 times that of ZIF-8 (α = 0.000). Density functional theory (DFT) calculations confirm that Zn–O–S with a larger bond angle (118.0°) was conducive to charge accumulation. Photoelectric test results show that CNCs can improve the electron transport ability and reduce the rate of photogenerated electron-hole complexation in ZIF-8. This work elucidated the mechanism of chiral auxiliaries in photocatalytic reduction of CO2 and provided a new strategy for photocatalytic reduction of CO2.