Tailoring defect-type and ligand-vacancies in Zr(iv) frameworks for CO2 photoreduction

The nature and degree of defects can fine-tune the light absorption energy (E-abs) and charge transfer energy (E-LMCT) of metal-organic frameworks (MOFs), which are important for photocatalytic reactions. Herein, a series of UiO-66-NH2 with missing-linker (ML)/missing-cluster (MC) defects and different degrees of ligand vacancies were synthesized and utilized to explore their photocatalytic performance of CO2 reduction. The photocatalytic CO yield of UiO-66-NH2-ML-100 with ML defects reaches 21.3 mu mol g(-1) h(-1), which is 2.2 times that of UiO-66-NH2-MC-150 with MC. Both experiments and density functional theory (DFT) calculations demonstrate that the nature of MC defects enlarges E-abs, while the ligand vacancy changes the coordination environment of Zr(iv) and lowers E-LMCT. More ligand vacancies per metal node lead to smaller E-LMCT, which is beneficial for the CO2 photoreduction reaction. This work provides a pathway to boost photocatalytic performance by tailoring the defects of MOFs.

Automated summary

This study investigates the photocatalytic performance of metal-organic frameworks (MOFs) in CO2 reduction by synthesizing UiO-66-NH2 with different types and degrees of defects. The results show that the nature and ligand vacancies of the defects play a crucial role in enhancing the photocatalytic activity. The findings suggest that tailoring the defects of MOFs can boost their photocatalytic performance.