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Hybrid Porous Polymers Combination of Octavinylsilsesquioxane/Pyrene with Benzothiadiazole Units for Robust Energy Storage and Efficient Photocatalytic Hydrogen Production from Water
We investigated the performance that is improved in various
applications
through molecular structural alterations. Specifically, we emphasized
the importance of controlling the branching densities of organic moieties
as a useful tactic for varying the surface area and porosity of hybrid
porous organic/inorganic polymers (HPPs), which include octavinylsilsesquioxane
(OVS) units. This study shows that adjusting the branching densities
could greatly enhance energy storage and hydrogen production. The
two-branched chemical structure (4,7-dibromo-2,1,3-benzothiadiazole,
BT-Br2) and the four-branched organic compound (1,1,2,2-tetrakis(4-bromophenyl)ethylene,
TPE-Br4) are individually reacted with OVS and 1,3,6,8-tetrabromopyrene
(Py-Br4) twice to prepare the HPPs. These materials with
high or low cross-linking density, as well as small and large surface
areas, are synthesized by this dual reaction, which also produces
HPPs with different cross-linking densities. Based on Brunauer–Emmett–Teller
calculations, the OVS-Py-BT HPP has more than 4.5 times larger surface
area than the OVS-Py-TPE HPP material. Remarkably, OVS-Py-BT HPP exhibited
exceptional results for supercapacitor applications, with specific
capacitance values of 248 and 54 F/g for OVS-Py-BT and OVS-Py-TPE
HPPs, respectively, as determined by galvanostatic charge–discharge.
OVS-Py-BT HPP significantly outperformed OVS-Py-TPE HPP in photocatalytic
hydrogen evolution. This is evident from their respective hydrogen
evolution rates: 1348 μmol g–1 h–1 for OVS-Py-BT HPP and a much lower 11.3 μmol g–1 h–1 for OVS-Py-TPE HPP