Abstract
An ideal material for photon harvesting must allow control of the exciton diffusion length and directionality. This is necessary in order to guide excitons to a reaction center, where their energy can drive a desired process. To reach this goal both of the following are required; short- and long-range structural order in the material and a detailed understanding of the excitonic transport. Here we present a strategy to realize crystalline chromophore assemblies with bespoke architecture. We demonstrate this approach by assembling anthracene dibenzoic acid chromophore into a highly anisotropic, crystalline structure using a layer-by-layer process. We observe two different types of photoexcited states; one monomer-related, the other excimer-related. By incorporating energy-accepting chromophores in this crystalline assembly at different positions, we demonstrate the highly anisotropic motion of the excimer-related state along the [010] direction of the chromophore assembly. In contrast, this anisotropic effect is inefficient for the monomer-related excited state.
Highlights
An ideal material for photon harvesting must allow control of the exciton diffusion length and directionality
The first step in our study of energy harvesting in SURMOFs was to identify a pair of organic linkers that satisfied both of the following criteria: (a) that they shared a similar length so that mixed or heterostructure SURMOFs could be fabricated without any major alteration of the structural order, and (b) exhibited the emission of one of the pair overlapped with the absorption of the other such that the spectral overlap necessary for Förtser resonant energy transfer (FRET) would be strong
SURMOF-2 can be viewed as consisting of an array of stacks of square grid type 2D sheets which are formed by connecting paddle-wheel type secondary building units (SBUs) with ditopic carboxylate functionalized organic linkers[28]
Summary
An ideal material for photon harvesting must allow control of the exciton diffusion length and directionality. By incorporating energy-accepting chromophores in this crystalline assembly at different positions, we demonstrate the highly anisotropic motion of the excimerrelated state along the [010] direction of the chromophore assembly. This anisotropic effect is inefficient for the monomer-related excited state. The applications for MOFs go far beyond gas storage and separation, and have demonstrated potential in engineering optoelectronic materials[22] Since these hybrid crystalline frameworks are assembled by combining metal or metal-oxo nodes and organic linkers, the number of possible architectures and topologies is enormous[23]. The importance of the chromophore organization on the directional long-range FRET hops and diffusion is discussed in detail
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