Construction of Porous Organic/Inorganic Hybrid Polymers Based on Polyhedral Oligomeric Silsesquioxane for Energy Storage and Hydrogen Production from Water

In this study, we used effective and one-pot Heck coupling reactions under moderate reaction conditions to construct two new hybrid porous polymers (named OVS-P-TPA and OVS-P-F HPPs) with high yield, based on silsesquioxane cage nanoparticles through the reaction of octavinylsilsesquioxane (OVS) with different brominated pyrene (P-Br4), triphenylamine (TPA-Br3), and fluorene (F-Br2) as co-monomer units. The successful syntheses of both OVS-HPPs were tested using various instruments, such as X-ray photoelectron (XPS), solid-state 13C NMR, and Fourier transform infrared spectroscopy (FTIR) analyses. All spectroscopic data confirmed the successful incorporation and linkage of P, TPA, and F units into the POSS cage in order to form porous OVS-HPP materials. In addition, the thermogravimetric analysis (TGA) and N2 adsorption analyses revealed the thermal stabilities of OVS-P-F HPP (Td10 = 444 °C; char yield: 79 wt%), with a significant specific surface area of 375 m2 g–1 and a large pore volume of 0.69 cm3 g–1. According to electrochemical three-electrode performance, the OVS-P-F HPP precursor displayed superior capacitances of 292 F g−1 with a capacity retention of 99.8% compared to OVS-P-TPA HPP material. Interestingly, the OVS-P-TPA HPP showed a promising HER value of 701.9 µmol g−1 h−1, which is more than 12 times higher than that of OVS-P-F HPP (56.6 µmol g−1 h−1), based on photocatalytic experimental results.

Porous organic polymers and porous organic hybrid polymers containing polyhedral oligomeric silsesquioxanes (POSS) have been immensely exercised in numerous applications, including hydrogen production, gas capture, chemical sensing catalysis, microelectronics, aerospace, iodine capture, biomedicine, water treatment, and energy storage [43][44][45][46][47][48]. In particular, cubic silsesquioxane molecules, which are considered an important kind of polyhedral oligomeric silsesquioxane, have attracted considerable attention in the scientific society, owing to their wonderful design from inorganic/organic hybrid materials, high surface area, tunable chemical properties, optical transparency, excellent mechanical toughness, and thermal stability [43][44][45][46][47][48][49][50][51][52]. The above molecules have a formula of (RSiO 1.5 ) with a nanoscale diameter of about 1-3 nm which contain inorganic cages in their structures that provide superior advantages, as mentioned before [53][54][55][56][57]. Subsequently, various preparation methods have been reported in order to synthesize porous polymers using cubic silsesquioxane molecules as the building unit, such as the Heck coupling reaction which achieves the demand of preparing clean and low-price materials with high-performance capabilities for energy storage devices and other applications. For example, Ervithayasuporn's group used a porous polymer nanocomposite based on OVS and porphyrin for capturing heavy metal anions and ions [58]. Zhang et al. prepared azo porous materials containing OVS as a cage and porphyrin for removing RhB and various metal ions from wastewater [59].
Motivated by these earlier reports, here, we have prepared two porous OVS-P-TPA and OVS-P-F HPPs with high yield using the Heck coupling reaction of the OVS cage with two different brominated comonomers (P/TPA and P/F) in the presence of Pd as a catalyst under moderate reaction conditions, as presented in Scheme 1. The molecular chemical structures, thermal stability (including temperature decomposition and carbon residues), crystallinities, surface morphologies, and porosity properties of the OVS-P-TPA and OVS-P-F HPPs were carefully investigated and discussed in detail using Brunauer-Emmett-Teller (BET) surface areas, X-ray photoelectron (XPS), and Fourier transforms infrared spectroscopy (FTIR) analyses. For the real application of these porous hybrid materials, two OVS-P-TPA and OVS-P-F HPPs were applied, and the electrochemical three-electrode performance and H 2 evolution from water splitting were assessed. The data revealed that the POSS-P-F HPP precursor displayed high specific capacitances of 292 F g −1 with a capacity retention of 99.8% compared to the POSS-P-TPA HPP material. Interestingly, the OVS-P-TPA HPP shows a promising HER value of 701.9 µmol g −1 h −1 based on photocatalytic experimental results. Scheme 1. Preparation route of (a) OVS-P-TPA HPP and (b) OVS-P-F HPP through the Heck coupling reaction.

Photocatalytic H 2 Evolution Experiment
In a typical measurement, 5 mg of OVS-P-TPA HPP or OVS-O-F HPP photocatalyst was dispersed by sonication in a 10 mL solution (water/MeOH (2/1)) containing 0.1 M ascorbic acid (AA), which was then inserted into the reaction glass container and sealed tightly with a rubber septum. Prior to illumination, the aerobic oxygen was removed from the sample by evacuating the solution mixture and then exposing it to a continuous stream of Ar gas for 30 min. The catalyst solution was exposed to light from a 350 W Xe lamp (1000 W m −2 ; λ > 380 nm) that had passed through a 380 nm band-pass filter. Using a gas-tight syringe, the hydrogen sample was taken every hour and injected in a Shimazhu GC-2014 gas chromatograph, using Ar as the carrier gas. Hydrogen was detected with a thermal conductivity detector, referring to the standard hydrogen gases with known concentrations [62,63].

Computational Details
The density functional theory (DFT) of the DMol3 code [64] was used in order to obtain the optimized structure and electronic properties. The generalized gradient approximation of the Perdew-Burke-Ernzerhof functional (GGA + PBE) was adopted throughout all the calculations [65]. The system's energy was converged to 10 −5 Ha, and the max force and the max displacements were 0.002 Ha/Å and 0.005 Å, respectively. In order to ensure self-consistent field (SCF) convergence accuracy, a self-consistent field (SCF) was converged to 10 −6 Ha. In addition to their electron densities, the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were computed [66].

Synthesis and Characterization of OVS-P-TPA and OVS-P-F HPPs
The preparation route of OVS-HPPs (OVS-P-TPA and OVS-P-F HPPs) is presented in Scheme 1. First, the P-Br 4 monomer was synthesized using the bromination reaction of P with Br 2 , using nitrobenzene as a solvent, as shown in Scheme S1. Secondly, TPA-Br 3 was easily synthesized through the reaction of TPA with Br 2 solution in DMF at 25 • C (see Scheme S2). Finally, F-Br 2 was prepared with a high yield through the reaction of the F molecule with Br 2 in CHCl 3 (see Scheme S3). The NMR and FTIR data of the P-Br 4 , TPA-Br 3, and F-Br 2 monomers in this study confirmed their successful synthesis [see the experimental part of this study]. Scheme 1 displays the synthesis route for the synthesis of our two new porous hybrid polymers (OVS-HPPs) based on the OVS unit (named OVS-P-TPA and OVS-P-F HPPs) via a simple and efficient Heck coupling reaction in a mixed solution containing DMF, K 2 CO 3 , and Pd as a catalyst. The mole ratios between all the monomers (OVS/TPA-Br 3 or F-Br 2 /P-Br 4 ), which were used in the preparation of the OVS-HPPs, was 1:3.8:0.1 [67]. We used this ratio to get a high surface area of these HPP materials and to increase the amount of pyrene moiety content as a donor unit in the HPP framework in order to adjust the energy band gap and investigate their potential applications in energy storage and hydrogen evolution. The OVS-P-TPA HPP was obtained through the reaction of OVS with P-Br 4 and TPA-Br 3 . This reaction produced OVS-P-TPA as a red powder [Scheme 1a]. OVS-P-F HPP was obtained through the reaction of OVS with P-Br 4 and F-Br 2 , which produced a yellow solid [Scheme 1b]. After completing the Heck coupling reaction, we revealed that the obtained OVS-HPP materials were not soluble in MeOH, H 2 O, DMF, DCM, THF, and acetone, indicating that our porous OVS-HPPs had a high crosslinking density and a high degree of polymerization. The matching bands for stretching Si-O-Si, C=C, and C=C-H groups in the OVS compound showed at 1107, 1600, and 3066 cm −1 , respectively, as shown in Figure 1a. According to Figure 1a,b, Figures S10 and S11, the band of the C-H aromatic in P-Br 4 , TPA-Br 3 , and F-Br 2 are represented at 3053, 3078, and 3056 cm −1 , respectively. Figure 1a,b, Figures S10 and S11 show that the peaks for aliphatic C-H and C=C units in the FTIR profiles of the OVS-P-TPA and OVS-P-F HPPs were found in the ranges of 2981-2964 and 1600-1590 cm −1 , respectively. As anticipated, the Si-O-Si absorption bands in both the OVS-P-TPA and the OVS-P-F HPPs (Figure 1a,b) were wider compared to the Si-O-Si unit in the OVS compound ( Figure 1). This was attributed to the development of cross-linked networks. Figure 1c reveals that the signal for aromatic carbons appeared in the range of 142-117 ppm for OVS-P-TPA HPP and 146-114 ppm for OVS-P-F HPP. The signal of the carbon nuclei of the C-N unit appeared at 146 ppm for OVS-P-TPA HPP. In addition, in the 13 C NMR solid-state profile, OVS-P-F HPP had a signal located at 36.6 ppm, corresponding to the CH 2 group. Moreover, the presence of OVS cage units in all the OVS-HPP materials was proven using 29 Si NMR solid-state profile ( Figure 1d). The two OVS-HPP samples displayed two signals centered near −14 and −80 ppm due to the Si-C=C and T 3 , respectively.  The surface chemical composition of OVS-P-TPA HPP and OVS-P-F HPP were detected in X-ray photoelectron spectroscopic (XPS) measurements. As can be seen in Figure Tables 1 and S1. The X-ray patterns (Figure S12) displayed amorphous characteristics for the OVS-HPPs materials. In addition, a gradual high X-ray diffraction peak can be seen at 2θ = 22° for the presence of Si-O-Si groups in the OVS cage [67].   Table 1 and Table S1. The X-ray patterns ( Figure S12) displayed amorphous characteristics for the OVS-HPPs materials. In addition, a gradual high X-ray diffraction peak can be seen at 2θ = 22 • for the presence of Si-O-Si groups in the OVS cage [67]. In order to confirm the porosity properties of the OVS-HPPs, the BET analyses were performed at 77 K and 1 bar (Figure 4). According to the IUPAC classification, the N2 isotherm profile for the OVS-P-TPA HPP sample (Figure 4a) was type III, and for the OVS-P-F HPP framework was the type I and IV (Figure 4b). OVS-P-TPA HPP contains mainly meso-and macro-pores, and OVS-P-F HPP shows a mix of micro-and mesopores at high relative pressures (P/P0 > 0.9), based on BET analyses. The specific surface area and total pore volumes of the OVS-P-TPA and OVS-P-F HPPs were 60 m 2 g −1 and 0.19 cm 3 , and 375 m 2 g −1 and 0.69 cm 3 g −1 , respectively (Table 1). We used the nonlocal density functional theory method to calculate the pore size distribution for the OVS-HPPs materials ( Figure  4c,d), and the pore diameters were found to be 2.56 and 2.20 nm, respectively, for the OVS-P-TPA and OVS-P-F HPPs. In addition, the relative content of micropores for the OVS-P-TPA and OVS-P-F HPPs was 0.12 and 0.21, respectively.  In order to confirm the porosity properties of the OVS-HPPs, the BET analyses were performed at 77 K and 1 bar (Figure 4). According to the IUPAC classification, the N 2 isotherm profile for the OVS-P-TPA HPP sample (Figure 4a) was type III, and for the OVS-P-F HPP framework was the type I and IV (Figure 4b). OVS-P-TPA HPP contains mainly meso-and macro-pores, and OVS-P-F HPP shows a mix of micro-and mesopores at high relative pressures (P/P0 > 0.9), based on BET analyses. The specific surface area and total pore volumes of the OVS-P-TPA and OVS-P-F HPPs were 60 m 2 g −1 and 0.19 cm 3 , and 375 m 2 g −1 and 0.69 cm 3 g −1 , respectively (Table 1). We used the nonlocal density functional theory method to calculate the pore size distribution for the OVS-HPPs materials (Figure 4c,d), and the pore diameters were found to be 2.56 and 2.20 nm, respectively, for the OVS-P-TPA and OVS-P-F HPPs. In addition, the relative content of micropores for the OVS-P-TPA and OVS-P-F HPPs was 0.12 and 0.21, respectively.  The shape and porosity parameters of the OVS-HPPs were evaluated using SEM and TEM measurements ( Figure 5). The OVS-P-TPA and OVS-P-F HPPs featured irregular aggregated sphere structures and aggregated irregular cloud-like structures, respectively, according to the SEM images (Figure 5a,b). Moreover, the TEM images of the OVS-HPP materials are shown in Figure 5c   The shape and porosity parameters of the OVS-HPPs were evaluated using SEM and TEM measurements ( Figure 5). The OVS-P-TPA and OVS-P-F HPPs featured irregular aggregated sphere structures and aggregated irregular cloud-like structures, respectively, according to the SEM images (Figure 5a,b). Moreover, the TEM images of the OVS-HPP materials are shown in Figure 5c  The shape and porosity parameters of the OVS-HPPs were evaluated using SEM and TEM measurements ( Figure 5). The OVS-P-TPA and OVS-P-F HPPs featured irregular aggregated sphere structures and aggregated irregular cloud-like structures, respectively, according to the SEM images (Figure 5a,b). Moreover, the TEM images of the OVS-HPP materials are shown in Figure 5c

Electrochemical Analysis of the OVS-P-TPA and OVS-P-F HPPs
A three-electrode setup was used to examine the electrochemical performance of the OVS-HPP materials (OVS-P-TPA and OVS-P-F HPPs) using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements. Figure 6a,b shows the CV curves of the two synthesized OVS-HPP frameworks and the configuration of the electrochemical cell used for the measurements. The voltage windows ranged from 0.00 to 1.00 V (vs. Hg/HgO) at a sweep speed ranging from 5 to 200 mV s −1 . Furthermore, when recorded at the highest scan rate of 200 mV s −1 , the CV curves of the OVS-HPP samples showed rectangleshaped shapes with the appearance of humps, indicating that this capacitive response was primarily caused by EDLC with a small amount of pseudocapacitance [2,12,35,69]. The integrated area of the OVS-P-F HPP sample was higher than that of the OVS-P-TPA HPP sample, revealing its superior electrochemical performance. This superior electrochemical performance of the OVS-P-F HPP sample was due to its high porosity properties [12]. Figure 6c,d presents the GCD curves of the OVS-P-TPA and OVS-P-F HPPs. The GCD curves of the OVS-HPP samples revealed triangular-like shapes with a slight bend at different current densities (0.5-20 A g −1 ), indicating the presence of pseudocapacitance and EDLC characteristics [2,12,35,69].

Electrochemical Analysis of the OVS-P-TPA and OVS-P-F HPPs
A three-electrode setup was used to examine the electrochemical performance of the OVS-HPP materials (OVS-P-TPA and OVS-P-F HPPs) using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements. Figure 6a,b shows the CV curves of the two synthesized OVS-HPP frameworks and the configuration of the electrochemical cell used for the measurements. The voltage windows ranged from 0.00 to 1.00 V (vs. Hg/HgO) at a sweep speed ranging from 5 to 200 mV s −1 . Furthermore, when recorded at the highest scan rate of 200 mV s −1 , the CV curves of the OVS-HPP samples showed rectangle-shaped shapes with the appearance of humps, indicating that this capacitive response was primarily caused by EDLC with a small amount of pseudocapacitance [2,12,35,69]. The integrated area of the OVS-P-F HPP sample was higher than that of the OVS-P-TPA HPP sample, revealing its superior electrochemical performance. This superior electrochemical performance of the OVS-P-F HPP sample was due to its high porosity properties [12]. Figure 6c,d presents the GCD curves of the OVS-P-TPA and OVS-P-F HPPs. The GCD curves of the OVS-HPP samples revealed triangular-like shapes with a slight bend at different current densities (0.5-20 A g −1 ), indicating the presence of pseudocapacitance and EDLC characteristics [2,12,35,69].  Figure 7a presents the capacitances of the OVS-HPPs determined using Equation (S1) (from the GCD curves). The OVS-P-F HPP sample displayed excellent capacitance (292 F g -1 ) among the tested OVS-P-TPA HPPs (72 F g -1 ) at 0.5 A g -1 . This behavior could be explained in terms of its higher surface area (375 m 2 g −1 ), and the existence of phenyl rings with abundant electrons, which make electrolytes more easily accessible to the surface of the electrode [2,12,35,69]. In addition, the capacitances of the OVS-HPP-based samples reduced as the current density increased from 0.5 to 20 A g −1 due to inadequate available time for ion diffusion and adsorption inside the tiniest pores inside a big particle at high current densities [3,12,69]. Additionally, compared to the other porous materials, the OVS-  Figure 7a presents the capacitances of the OVS-HPPs determined using Equation (S1) (from the GCD curves). The OVS-P-F HPP sample displayed excellent capacitance (292 F g -1 ) among the tested OVS-P-TPA HPPs (72 F g -1 ) at 0.5 A g -1 . This behavior could be explained in terms of its higher surface area (375 m 2 g −1 ), and the existence of phenyl rings with abundant electrons, which make electrolytes more easily accessible to the surface of the electrode [2,12,35,69]. In addition, the capacitances of the OVS-HPP-based samples reduced as the current density increased from 0.5 to 20 A g −1 due to inadequate available time for ion diffusion and adsorption inside the tiniest pores inside a big particle at high current densities [3,12,69]. Additionally, compared to the other porous materials, the OVS-P-F HPP-based material showed good capacitance (Table S2) [12,35,[69][70][71]. GCD measurements were used to examine the stability of the OVS-HPP samples after 2000 cycles at 10 A g −1 (Figure 7b). The OVS-P-TPA and OVS-P-F HPP samples displayed good cycling stability (Figure 7b), with 98.1 and 99.8% retention, respectively. The Ragone plot (Figure 7c) showed that the energy densities of the OVS-P-TPA and OVS-P-F HPP samples were 10.02 and 40.5 Wh Kg −1 , respectively. P-F HPP-based material showed good capacitance (Table S2) [12,35,[69][70][71]. GCD measurements were used to examine the stability of the OVS-HPP samples after 2000 cycles at 10 A g −1 (Figure 7b). The OVS-P-TPA and OVS-P-F HPP samples displayed good cycling stability (Figure 7b), with 98.1 and 99.8% retention, respectively. The Ragone plot ( Figure  7c) showed that the energy densities of the OVS-P-TPA and OVS-P-F HPP samples were 10.02 and 40.5 Wh Kg −1 , respectively.

Photocatalytic Performance of OVS-P-TPA HPP and OVS-P-F HPP for H2 Production
The ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was used to investigate the light absorption properties of the polymers, as shown in Figure 8a. The two polymers demonstrated good absorption in the visible light region, indicating their ability to harvest large amounts of visible light during the photocatalytic reaction. The onset of the absorption spectrum of the two polymers approximately reached 600 and 650 nm for OVS-P-F HPP and OVS-P-TPA HPP, respectively. The bandgap (Eg) of the polymers was determined from the Tauc plot of (αhν) 2 versus (hν) from the UV-Vis spectra and by extrapolation of the linear part of the curve to the energy axis in order to obtain the optical bandgap based on the equation: αhν = A(hν − Eg) γ , where α is the absorption coefficient, A is an energy-independent constant, Eg is the optical band gap, h is the plank constant, v is the velocity, and γ is the electronic transition. As shown in Figure 8b, the Eg values of the OVS-P-F HPP and OVS-P-TPA HPP polymers were calculated to be 2.26 and 2.16 eV, respectively. Next, we tested the polymers as photocatalysts for light-driven hydrogen evolution. In the presence of AA as a sacrificial reagent and without a Pt co-catalyst, we recorded the hydrogen evolution kinetic curve to explore the H2 evolution efficiency of the polymer photocatalyst, as shown in Figure 8c. The hydrogen evolution rate (HER) was obtained from the kinetic curves (Figure 8d). The total amount of H2 produced by the OVS-P-TPA HPP and OVS-P-F HPP polymer photocatalysts reached 2000 and 185 µ mol/g after 4 h of the reaction, respectively (Figure 8c). The HER was calculated for the two polymers from the kinetic curve presented in Figure 8d. The OVS-P-TPA HPP sample shows a promising HER value of 701.9 µ mol g −1 h −1 , which is more than 12 times higher than that of OVS-P-F HPP (56.6 µ mol g −1 h −1 ). The high HER value of OVS-P-TPA HPP is due to the donor-acceptor structure between the pyrene and triphenylamine moieties of the OVS-P-

Photocatalytic Performance of OVS-P-TPA HPP and OVS-P-F HPP for H 2 Production
The ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was used to investigate the light absorption properties of the polymers, as shown in Figure 8a. The two polymers demonstrated good absorption in the visible light region, indicating their ability to harvest large amounts of visible light during the photocatalytic reaction. The onset of the absorption spectrum of the two polymers approximately reached 600 and 650 nm for OVS-P-F HPP and OVS-P-TPA HPP, respectively. The bandgap (E g ) of the polymers was determined from the Tauc plot of (αhν) 2 versus (hν) from the UV-Vis spectra and by extrapolation of the linear part of the curve to the energy axis in order to obtain the optical bandgap based on the equation: αhν = A(hν − E g ) γ , where α is the absorption coefficient, A is an energy-independent constant, E g is the optical band gap, h is the plank constant, v is the velocity, and γ is the electronic transition. As shown in Figure 8b, the E g values of the OVS-P-F HPP and OVS-P-TPA HPP polymers were calculated to be 2.26 and 2.16 eV, respectively. Next, we tested the polymers as photocatalysts for light-driven hydrogen evolution. In the presence of AA as a sacrificial reagent and without a Pt co-catalyst, we recorded the hydrogen evolution kinetic curve to explore the H 2 evolution efficiency of the polymer photocatalyst, as shown in Figure 8c. The hydrogen evolution rate (HER) was obtained from the kinetic curves (Figure 8d). The total amount of H 2 produced by the OVS-P-TPA HPP and OVS-P-F HPP polymer photocatalysts reached 2000 and 185 µmol/g after 4 h of the reaction, respectively (Figure 8c). The HER was calculated for the two polymers from the kinetic curve presented in Figure 8d. The OVS-P-TPA HPP sample shows a promising HER value of 701.9 µmol g −1 h −1 , which is more than 12 times higher than that of OVS-P-F HPP (56.6 µmol g −1 h −1 ). The high HER value of OVS-P-TPA HPP is due to the donor-acceptor structure between the pyrene and triphenylamine moieties of the OVS-P-TPA HPP polymer, leading to separation of the charge carrier and then the enhancement of photocatalytic activity.
TPA HPP polymer, leading to separation of the charge carrier and then the enhancement of photocatalytic activity. To determine how the donor and acceptor fragments influenced the photoelectric properties of the examined compounds, we calculated the charge density of the high occupied molecular orbital (HOMO) and low unoccupied molecular orbital (LUMO) energy levels using the density functional theory (DFT) of the DMol3 code. Figure 9 shows that highly pronounced spatial separation of the HOMOs and LUMOs can be observed for OVS-P-TPA HPP in contrast to OVS-P-F HPP. The LUMO orbital in the OVS-P-TPA HPP sample was mainly localized over the pyrene donor, whereas the HOMO orbital was localized over the triphenyl acceptor. On the other hand, in the case of the OVS-P-F HPP polymer, the HOMO and LUMO orbitals were localized over the pyrene moiety, and no charge separation was observed. Thus, we expect that OVS-P-TPA HPP has a better ability to separate the photogenerated e-/h+ pairs and higher photocatalytic efficiency than other molecules. This distribution indicates high electron delocalization, and significant charge transfer (CT) occurs inside the investigated molecule under light irradiation. To determine how the donor and acceptor fragments influenced the photoelectric properties of the examined compounds, we calculated the charge density of the high occupied molecular orbital (HOMO) and low unoccupied molecular orbital (LUMO) energy levels using the density functional theory (DFT) of the DMol3 code. Figure 9 shows that highly pronounced spatial separation of the HOMOs and LUMOs can be observed for OVS-P-TPA HPP in contrast to OVS-P-F HPP. The LUMO orbital in the OVS-P-TPA HPP sample was mainly localized over the pyrene donor, whereas the HOMO orbital was localized over the triphenyl acceptor. On the other hand, in the case of the OVS-P-F HPP polymer, the HOMO and LUMO orbitals were localized over the pyrene moiety, and no charge separation was observed. Thus, we expect that OVS-P-TPA HPP has a better ability to separate the photogenerated e−/h+ pairs and higher photocatalytic efficiency than other molecules. This distribution indicates high electron delocalization, and significant charge transfer (CT) occurs inside the investigated molecule under light irradiation.

Conclusions
In this study, we successfully constructed and designed OVSP-TPA HPP and POSS-P-F HPP using simple Heck coupling under moderate and suitable reaction conditions through the reaction of an OVS inorganic cage with brominated P/TPA or P/F as comonomers. All spectroscopic results revealed the successful syntheses of both OVS-HPPs with good yield. The POSS-P-F HPP sample had a Td10 of 444 °C, with a char yield of 79 wt%, as well as a high specific surface area of 375 m 2 g -1 and a pore volume of 0.69 cm 3 g -1 .
According to electrochemical three-electrode performance, the POSS-P-TPA and POSS-P-F HPPs precursor capacitances were 72 and 292 F g −1 , respectively. Furthermore, the OVS-P-TPA HPP had a promising HER value of 701.9 µ mol g −1 h −1 due to the donor-acceptor structure that was obtained between the P and TPA moieties of the OVS-P-TPA HPP.

Conclusions
In this study, we successfully constructed and designed OVSP-TPA HPP and POSS-P-F HPP using simple Heck coupling under moderate and suitable reaction conditions through the reaction of an OVS inorganic cage with brominated P/TPA or P/F as comonomers. All spectroscopic results revealed the successful syntheses of both OVS-HPPs with good yield. The POSS-P-F HPP sample had a T d10 of 444 • C, with a char yield of 79 wt%, as well as a high specific surface area of 375 m 2 g -1 and a pore volume of 0.69 cm 3 g -1 . According to electrochemical three-electrode performance, the POSS-P-TPA and POSS-P-F HPPs precursor capacitances were 72 and 292 F g −1 , respectively. Furthermore, the OVS-P-TPA HPP had a promising HER value of 701.9 µmol g −1 h −1 due to the donor-acceptor structure that was obtained between the P and TPA moieties of the OVS-P-TPA HPP.
Supplementary Materials: The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/polym15010182/s1, Scheme S1: Synthesis of P-Br 4 from pyrene in the presence of Br 2 ; Scheme S2: Synthesis of TPA-Br 3 from TPA in the presence of NBS and DMF as a solvent; Scheme S3: Synthesis of F-Br 2 from fluorene in the presence of Br 2 ; Figure S1: FTIR spectrum of P-Br 4 ; Figure S2: DSC profile of TPA-Br 3 ; Figure S3: FTIR spectrum of TPA-Br 3 ; Figure S4: 1 H NMR spectrum of TPA-Br 3 ; Figure S5: 13 C NMR spectrum of TPA-Br 3 ; Figure S6: DSC profile of F-Br 2 ; Figure S7: FTIR spectrum of F-Br 2 ; Figure S8: 1 H NMR spectrum of F-Br 2 ; Figure S9: 13 C NMR spectrum of F-Br 2 ; Figure S10: FTIR analyses of OVS, P-Br 4 , TPA-Br 3 , and OVS-P-TPA HPP; Figure S11: FTIR analyses of OVS, P-Br 4 , F-Br 2 , and OVS-P-F HPP; Figure S12: XRD patterns of OVS-P-TPA and OVS-P-F HPPs; Table S1: TGA data of OVS-HPPs and synthesized monomers in this study; Table S2: Summarizes the specific capacitances of POSS-P-TPA HPP and POSS-P-F HPP compared to other organic and inorganic porous materials.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.