Visible-light-induced photocatalytic CO reduction over zirconium metal organic frameworks modified with different functional groups.

The reduction of CO into high value-added chemicals and fuels by a photocatalytic technology can relieve energy shortages and the environmental problems caused by greenhouse effects. In the current work, an amino-functionalized zirconium metal organic framework (Zr-MOF) was covalently modified with different functional groups via the condensation of Zr-MOF with 2-pyridinecarboxaldehyde (PA), salicylaldehyde (SA), benzaldehyde (BA), and trifluoroacetic acid (TA), named Zr-MOF-X (X = PA, SA, BA, and TA), respectively, through the post-synthesis modification. Compared with Zr-MOF and Zr-MOF-TA, the introduction of PA, SA, or BA into the framework of Zr-MOF can not only enhance the visible-light harvesting and CO capture, but also accelerate the photogenerated charge separation and transfer, thereby improving the photocatalytic ability of Zr-MOF for CO reduction. These results indicate that the modification of Zr-MOF with electron-donating groups can promote the photocatalytic CO reduction. Therefore, the current work provides an instructive approach to improve the photocatalytic efficiency of CO reduction through the covalent modification of MOFs.