Abstract
The molecular-level structuration of two full photosystems into conjugated porous organic polymers is reported. The strategy of heterogenization gives rise to photosystems which are still fully active after 4 days of continuous illumination. Those materials catalyze the carbon dioxide photoreduction driven by visible light to produce up to three grams of formate per gram of catalyst. The covalent tethering of the two active sites into a single framework is shown to play a key role in the visible light activation of the catalyst. The unprecedented long-term efficiency arises from an optimal photoinduced electron transfer from the light harvesting moiety to the catalytic site as anticipated by quantum mechanical calculations and evidenced by in situ ultrafast time-resolved spectroscopy.
Highlights
In the perspective of green fuel production, non-restrictive photochemical processes using visible light as sole energy source open the appealing opportunity of a very low carbon footprint
We have chosen monomers based on photoactive perylene or pyrene cores to synthesize microporous macroligands[5,25,26] that consist of alternating photosensitizers and metal binding sites called hereafter Perylene-altBipyridine-Conjugated Microporous Polymers (PerBpyCMP) and Pyrene-alt-Bipyridine-CMP (PyBpyCMP)
In PerBpyCMP-based materials, the photo-excited electron occupies mostly a local excited state centred on the perylene moiety (Figure 2a), whereas in PyBpyCMP-based materials it is delocalized between bipyridine and pyrene orbitals (Figure 2a), populating in an internal charge transfer state
Summary
In the perspective of green fuel production, non-restrictive photochemical processes using visible light as sole energy source open the appealing opportunity of a very low carbon footprint. Metal-free clusters, the Rh coordination triggers a chromophore-to-bipyridine controlled HOMO-LUMO transition.[33] after, light absorption and relaxation processes, the photo-excited electron should be centred next to the catalytically active Rh moiety representing an efficient charge separation.
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