Photoreactive Carbon Dioxide Capture by a Zirconium–Nanographene Metal–Organic Framework

• Published in: The journal of physical chemistry letters 2023-05, Vol.14 (18), p.4334-4341
• Main Authors: Zheng, Xin, Drummer, Matthew C., He, Haiying, Rayder, Thomas M., Niklas, Jens, Weingartz, Nicholas P., Bolotin, Igor L., Singh, Varun, Kramar, Boris V., Chen, Lin X., Hupp, Joseph T., Poluektov, Oleg G., Farha, Omar K., Zapol, Peter, Glusac, Ksenija D.
• Format: Article
• Language: English
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; photocatalytic CO2 reduction mechanism; Physical Insights into Chemistry, Catalysis, and Interfaces; Zirconium metal-organic framework
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.3c00049

The mechanism of photochemical CO2 reduction to formate by PCN-136, a Zr-based metal–organic framework (MOF) that incorporates light-harvesting nanographene ligands, has been investigated using steady-state and time-resolved spectroscopy and density functional theory (DFT) calculations. The catalysis was found to proceed via a “photoreactive capture” mechanism, where Zr-based nodes serve to capture CO2 in the form of Zr–bicarbonates, while the nanographene ligands have a dual role of absorbing light and storing one-electron equivalents for catalysis. We also find that the process occurs via a “two-for-one” route, where a single photon initiates a cascade of electron/hydrogen atom transfers from the sacrificial donor to the CO2-bound MOF. The mechanistic findings obtained here illustrate several advantages of MOF-based architectures in molecular photocatalyst engineering and provide insights on ways to achieve high formate selectivity.