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Light-Harvesting and Ultrafast Energy Migration in Porphyrin-Based Metal–Organic Frameworks

2012; American Chemical Society; Volume: 135; Issue: 2 Linguagem: Inglês

10.1021/ja310596a

1943-2984

Ho‐Jin Son, Shengye Jin, Sameer Patwardhan, Sander J. Wezenberg, Nak Cheon Jeong, Monica C. So, Christopher E. Wilmer, Amy A. Sarjeant, George C. Schatz, Randall Q. Snurr, Omar K. Farha, Gary P. Wiederrecht, Joseph T. Hupp,

Perovskite Materials and Applications

Given that energy (exciton) migration in natural photosynthesis primarily occurs in highly ordered porphyrin-like pigments (chlorophylls), equally highly ordered porphyrin-based metal-organic frameworks (MOFs) might be expected to exhibit similar behavior, thereby facilitating antenna-like light-harvesting and positioning such materials for use in solar energy conversion schemes. Herein, we report the first example of directional, long-distance energy migration within a MOF. Two MOFs, namely F-MOF and DA-MOF that are composed of two Zn(II) porphyrin struts [5,15-dipyridyl-10,20-bis(pentafluorophenyl)porphinato]zinc(II) and [5,15-bis[4-(pyridyl)ethynyl]-10,20-diphenylporphinato]zinc(II), respectively, were investigated. From fluorescence quenching experiments and theoretical calculations, we find that the photogenerated exciton migrates over a net distance of up to ~45 porphyrin struts within its lifetime in DA-MOF (but only ~3 in F-MOF), with a high anisotropy along a specific direction. The remarkably efficient exciton migration in DA-MOF is attributed to enhanced π-conjugation through the addition of two acetylene moieties in the porphyrin molecule, which leads to greater Q-band absorption intensity and much faster exciton-hopping (energy transfer between adjacent porphyrin struts). The long distance and directional energy migration in DA-MOF suggests promising applications of this compound or related compounds in solar energy conversion schemes as an efficient light-harvesting and energy-transport component.