Tailored Persistent Radical-containing Heterotrimetal-Organic Framework for Boosting Efficiency of Visible/NIR Light-driven Photocatalytic CO₂ Reduction

Promoting light absorption range of photocatalysts is of great significance to improve solar light-driven photocatalytic CO2 reduction efficiency. Herein, a new viologen-based multicomponent heterotrimetallic metal-organic framework (MOF) [Cu3Th6(mu(3)-O)(4)(mu(3)-OH)(4)(cpb)(12)][Fe-III(CN)(6)](6) (IHEP-14) with an unprecedented (6, 18)-connected she-d topology is presented. Upon UV irradiation, this MOF undergoes ligand and iron photoreduction, and a single-crystal-to-single-crystal transformation to generate persistent radical-containing MOF [Cu3Th6(mu(3)-O)(4)(mu(3)-OH)(4)(cpb(center dot))(12)][Fe-II(CN)(6)](6) (IHEP-15). This radical-containing MOF shows excellent stability without fading after at least 2 months in air. Besides extending the photoabsorption to a wider wavelength range covering from 200 to 2,500 nm, the generation of persistent radical in IHEP-15 also largely enhances its CO2 adsorption capacity by a factor of three due to the strong affinity between pi orbital of the radical and the pi system of CO2. These attributes endow IHEP-15 with excellent visible/NIR light-driven CO2 photoreduction activity, with CO production rates under visible and NIR irradiation of 570.3 and 209.3 mu mol h(-1) g(-1), respectively. Notably, the latter is a record high for NIR-induced CO production among all MOFs reported so far.