A pore-expanded supramolecular organic framework and its enrichment of photosensitizers and catalysts for visible-light-induced hydrogen production

A pore-expanded three-dimensional supramolecular organic framework SOF-bpb, with a previously unattained aperture size of 3.6 nm, has been constructed in water from the co-assembly of cucurbit[8] uril (CB[8]) and a tetraphenylmethane-cored 1,4-bis(pyridin-4-yl)-benzene-appended building block M1. The periodicity of SOF-bpb in water and in the solid state has been confirmed using synchrotron X-ray scattering and diffraction experiments. SOF-bpb can adsorb anionic and neutral Ru2+ complex photosensitizers and anionic Wells-Dawson-type and Keggin-type polyoxometalates (POMs). The adsorption leads to an important enrichment effect, which remarkably increases the catalytic efficiency of the Ru2+ complex-POM systems for visible light-induced reduction of protons to produce H2. The expanded aperture of SOF-bpb also facilitates light absorption of the adsorbed Ru2+ complex photosensitizers and electron transfer between excited complexes and the POM catalysts, leading to enhanced photocatalytic activities as compared with the prototypical SOF that has an aperture size of 2.1 nm.