Key points are not available for this paper at this time.
Electronic structure calculations show that guest C60 in the porphyrin-containing metal organic frameworks Zn2(TCPB)(DA-ZnP) (DA-MOF; H4TCPB = 1,2,4,5-tetrakis(4-carboxyphenyl)benzene, DA-ZnP = 5,15-bis[(4-pyridyl)ethynyl-10,20-diphenylporphinato]zinc(II)) and Zn2(TCPB)(F-ZnP) (F-MOF; F-ZnP = 5,15-di(4-pyridyl)-10,20-bis(pentafluorophenyl)porphinatozinc(II)) engenders high photoelectrical conductivity due to efficient donor–acceptor charge-transfer (CT) interactions. Structural modifications at the meso position of the porphyrin influence the preferred positions of C60 within the frameworks, giving rise to host–guest interactions with different anisotropic structural, electronic, and optoelectronic properties. A preferred slipped-parallel π-stacked interaction of C60 that is predicted for NH2-substituted DA-MOF and F-MOF fosters strong CT transitions and lowers band gaps by ∼1.0 eV compared to the pristine DA-MOF and F-MOF. Hopping rates computed using Marcus theory are found to be anisotropic and accelerated by multiple orders of magnitude across π-stacked interfaces created by C60 incorporation, a consequence of strong electronic coupling between initial and final diabatic states. Calculations indicate that photoinduced electron transfer, as well as direct CT from porphyrin to C60 upon irradiation, triggers a charge separation process that leads to the formation of what should be long-lived electron-trapped states at the heterojunctions. Design principles revealed here for the control of photophysical and electron-transfer processes will be useful for constructing new MOF-derived visible- and infrared-based optoelectronics.
Pratik et al. (Mon,) studied this question.