Determination of Singlet Oxygen Quantum Yield of a Porphyrinic Metal–Organic Framework
Yajiao Hao, Brandon M. Liu, Timothy F. Bennett, Charlotte G. Monsour, Matthias Selke, Yangyang Liu
Abstract
Metal–organic frameworks (MOFs) have emerged as heterogeneous photosensitizers in applications ranging from photodynamic therapy to photocatalysis. However, singlet oxygen (1O2) quantum yields of MOF photosensitizers are largely unknown. Herein, we report a reliable method to quantify the 1O2 quantum yield of a porphyrin MOF PCN-222/MOF-545 (free base). To accurately measure the optical density of the MOF suspensions in chloroform, a UV–vis spectrometer equipped with an integrating sphere detector was employed. However, no 1O2 near-infrared luminescence signal from the excited MOF could be detected and the amount of 1O2 produced by the MOF photosensitizer was quantified using a 1O2 trap 9,10-dimethylanthracene. Using C70 as a reference, the 1O2 quantum yield of PCN-222/MOF-545 (free base) was determined to be 0.35 ± 0.02. This method should be applicable to the determination of 1O2 quantum yields of other solid-state materials.