Abstract
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-Br-2) and the four-branched organic compound (1,1,2,2-tetrakis(4-bromophenyl)ethylene, TPE-Br-4) are individually reacted with OVS and 1,3,6,8-tetrabromopyrene (Py-Br-4) 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 mu mol g(-1) h(-1) for OVS-Py-BT HPP and a much lower 11.3 mu mol g(-1) h(-1) for OVS-Py-TPE HPP.