Author: Son HJ, Jin S, Patwardhan S, Wezenberg SJ, Jeong NC, So M, Wilmer CE, Sarjeant AA, Schatz GC, Snurr RQ, Farha OK, Wiederrecht GP, Hupp JT.
Affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
Conference/Journal: J Am Chem Soc.
Date published: 2013 Jan 16
Other:
Volume ID: 135 , Issue ID: 2 , Pages: 862-9 , Special Notes: doi: 10.1021/ja310596a , Word Count: 203
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.
PMID: 23249338