Design Hybrid Porous Organic/Inorganic Polymers Containing Polyhedral Oligomeric Silsesquioxane/Pyrene/Anthracene Moieties as a High-Performance Electrode for Supercapacitor

We synthesized two hybrid organic–inorganic porous polymers (HPP) through the Heck reaction of 9,10 dibromoanthracene (A-Br2) or 1,3,6,8-tetrabromopyrene (P-Br4)/A-Br2 as co-monomers with octavinylsilsesquioxane (OVS), in order to afford OVS-A HPP and OVS-P-A HPP, respectively. The chemical structures of these two hybrid porous polymers were validated through FTIR and solid-state 13C and 29Si NMR spectroscopy. The thermal stability and porosity of these materials were measured by TGA and N2 adsorption/desorption analyses, demonstrating that OVS-A HPP has higher thermal stability (Td10: 579 °C) and surface area (433 m2 g−1) than OVS-P-A HPP (Td10: 377 °C and 98 m2 g−1) due to its higher cross-linking density. Furthermore, the electrochemical analysis showed that OVS-P-A HPP has a higher specific capacitance (177 F g −1 at 0.5 A F g−1) when compared to OVS-A HPP (120 F g −1 at 0.5 A F g−1). The electron-rich phenyl rings and Faradaic reaction between the π-conjugated network and anthracene moiety may be attributed to their excellent electrochemical performance of OVS-P-A HPP.


Introduction
The disparity between the rising energy demand and the stagnant supply has resulted in a worldwide energy crisis [1][2][3][4][5]. The fast production and excessive use of fossil fuels have opened an urgent demand for providing solutions to environmental challenges. Therefore, there is a great need to innovate sustainable and effective energy storage methods [6][7][8][9][10].
Scientists have sought to address this problem by developing renewable energy storage methods. Supercapacitors (SCs) are one of the most practical approaches to addressing energy scarcity [11][12][13], and they have a high energy density, excellent durability, a quick charge/discharge mechanism, and significant stability [14][15][16]. In SCs, energy may be stored in two different ways; the first is the non-faradaic method, in which the ionic charges are gathered electrostatically at the electrolyte-electrode interface. In contrast, in the faradaic method, the activity occurs at the solid surface and involves a reversible redox reaction [17,18]. The electrode material is regarded as one of the main criteria influencing the effectiveness of SCs [19]. Thus, many inorganic, organic, and hybrid organic-inorganic materials have been used as electrode materials for SCs [20][21][22][23][24].

Characterization, Thermal Stability, Porosity, and Morphology of OVS-A HPP and OVS-P-A HPP
The synthesis of two different hybrids of organic-inorganic HPP (OVS-A HPP and OVS-P-A HPP) is shown in Scheme 1. We synthesized A-Br 2 through the reaction of anthracene and Br 2 with chloroform at 50 • C for 4 h (Scheme S1). Then, we prepared P-Br 4 by the reaction of pyrene with a neat Br 2 solution in nitrobenzene at 120 • C for 24 h (Scheme S2). Finally, we prepared OVS-A HPP and OVS-P-A HPP through the heck reaction of A-Br 2 and P-Br 4 /A-Br 2 , respectively, with OVS, DMF, Pd(PPh 3 ) 4 and K 2 CO 3 at 110 • C for 72 h (Scheme 1). All organic solvents showed a low solubility for these OVS-HPPs frameworks (Scheme 1), which is evident in the fact that the Heck reactions were effective, leading to the development of highly crosslinked OVS materials. The chemical structures of OVS-A HPP and OVS-P-A HPP were verified through FTIR and solid-state 13 C and 29 Si spectroscopy, as shown in Figure 1. The absorption bands at 3113 cm −1 , 3067 cm −1 , 1610 cm −1 , and 1108 cm −1 were found in the spectra of OVS, representing the bond stretching of C=CH, C=C, and Si-O-Si, respectively. The absorption band for A-Br 2 , P-Br 4 , OVS-A HPP, and OVS-P-A HPP were observed at 3073 cm −1 , 3031 cm −1 , 3079 cm −1 , and 3065 cm −1 , corresponding to C-H aromatics, respectively (Figure 1a,b). The development of cross-linked networks was also observed in both porous materials (OVS-A HPP, and OVS-P-A HPP), as the absorption spectra of the Si-O-Si unit were wider than that of OVS (Figure 1a,b). Furthermore, due to water absorption, both OVS-A HPP and OVS-P-A HPP featured OH groups in their FTIR spectra. According to the solid-state 13 C NMR results of the OVS-A HPP and OVS-P-A HPP (Figure 1c), the carbon nuclei signals were found in the range 137-131 ppm and 148-127 ppm, respectively, representing aromatic carbons and C=C groups in both porous OVS-HPP-based materials. Additionally, solid-state 29 Si NMR analysis was used to verify the functional groups of OVS in the OVS-A HPP and OVS-P-A HPP structures. Figure 1d displays the signals that appeared near −11.2 ppm and −80.2 ppm, corresponding to Si-C=C and T 3 groups, respectively, for the OVS cage in the OVS-A HPP and OVS-P-A HPP.  13 C and (d) 29 Si NMR spectra of the OVS-A HPP and OVS-P-A HPP. * is the side band of solid-state nuclear magnetic resonance spectroscopy (NMR).
We performed X-ray photoelectron spectroscopy (XPS) to confirm the presence of Si, O, and C elements in OVS-A HPP and OVS-P-A HPP ( Figure 2). We observed Si2p, Si2s, C1s, and O1s signals corresponding to 103 eV, 155 eV, 284 eV, and 532 eV for OVS-A HPP, respectively (Figure 2a), and 103 eV, 156 eV, 284 eV and 534 eV for OVS-P-A HPP, respec-  13 C and (d) 29 Si NMR spectra of the OVS-A HPP and OVS-P-A HPP. * is the side band of solid-state nuclear magnetic resonance spectroscopy (NMR).
We performed X-ray photoelectron spectroscopy (XPS) to confirm the presence of Si, O, and C elements in OVS-A HPP and OVS-P-A HPP ( Figure 2). We observed Si2p, Si2s, C1s, and O1s signals corresponding to 103 eV, 155 eV, 284 eV, and 532 eV for OVS-A HPP, respectively ( Figure  TGA analysis was used to measure the thermal stability and char yield of OVS-A HPP and OVS-P-A HPP (Figure 3). The thermal decomposition temperatures (Td5, Td10) and char yield for OVS were observed as 240 °C, 255 °C, and 4 wt%, respectively. The corresponding values for A-Br2 were 219 °C, 234 °C, and 0 wt%, whereas those for P-Br4 were 321 °C, 350 °C, and 0 wt%, respectively. We found that the developed hybrid porous material's thermal stability and char yield were greatly enhanced after the heck reaction, due to the cross-linking of OVS with A-Br2 and P-Br4/A-Br2. The OVS-A HPP experienced a thermal stability of (Td5, Td10) 473 °C, 579 °C, and a char yield of 83 wt%; meanwhile, for OVS-P-A HPP, they were 317 °C, 377 °C, and 73 wt%, respectively. The thermal stability and char yield of OVS-A HPP was higher than that of OVS-P-A HPP due to its higher cross-linking density. The thermal properties of two hybrid porous materials are summarized in Table 1. TGA analysis was used to measure the thermal stability and char yield of OVS-A HPP and OVS-P-A HPP ( Figure 3). The thermal decomposition temperatures (T d5 , T d10 ) and char yield for OVS were observed as 240 • C, 255 • C, and 4 wt%, respectively. The corresponding values for A-Br 2 were 219 • C, 234 • C, and 0 wt%, whereas those for P-Br 4 were 321 • C, 350 • C, and 0 wt%, respectively. We found that the developed hybrid porous material's thermal stability and char yield were greatly enhanced after the heck reaction, due to the cross-linking of OVS with A-Br 2 and P-Br 4/ A-Br 2 . The OVS-A HPP experienced a thermal stability of (T d5 , T d10 ) 473 • C, 579 • C, and a char yield of 83 wt%; meanwhile, for OVS-P-A HPP, they were 317 • C, 377 • C, and 73 wt%, respectively. The thermal stability and char yield of OVS-A HPP was higher than that of OVS-P-A HPP due to its higher cross-linking density. The thermal properties of two hybrid porous materials are summarized in Table 1.  The porosity properties of OVS-A HPP and OVS-P-A HPP were measured by N2 adsorption/desorption (Figure 4a,b, and Table 1 Table 1).  The porosity properties of OVS-A HPP and OVS-P-A HPP were measured by N 2 adsorption/desorption (Figure 4a,b, and Table 1). The OVS-A HPP exhibited type II adsorption isotherm features, while the OVS-P-A HPP exhibited type II and IV according to the IUPAC classifications. The OVS-A HPP and OVS-P-A HPP exhibited rapid N 2 absorption uptake potentials in the low and high-pressure zones, indicating the presence of microporous and mesoporous in their structures. Furthermore, the surface area (S BET ) of OVS-A HPP (433 m 2 g −1 ) was found to be higher than that of OVS-P-A HPP (98 m 2 g −1 ). The OVS-A HPP and OVS-P-A HPP had mean pore diameters of ca. 2 nm and 2.5 nm, respectively, and their total pore volumes were 1.1 cm 3 g −1 and 0.3 cm 3 g −1 , respectively (Figure 4c,d and Table 1).   Figure S3). The SEM images of OVS-A HPP showed tered small spheres ( Figure S3a), while for OVS-P-A HPP, we observed clustered irr larly shaped columnar and spheres ( Figure S3b). The element mapping and energy persive X-ray (EDX) analyses of SEM images confirmed the existence of C, N, and O a (Figures 5 and 6). The corresponding weight percentages of C, N, and O atoms were fo to be 48.3, 16.1, and 36% for OVS-A HPP, and 33.2, 13.3, and 54% for OVS-P-A HPP. thermore, the morphology of hybrid porous materials was further confirmed by the images (Figure S3c,d)). These images show small pores, confirming porous structure dark and bright patches representing amorphous characteristics in OVS-A HPP and O P-A HPP. The morphological and porous properties of OVS-A HPP and OVS-P-A HPP were investigated by SEM and TEM ( Figure S3). The SEM images of OVS-A HPP showed clustered small spheres ( Figure S3a), while for OVS-P-A HPP, we observed clustered irregularly shaped columnar and spheres ( Figure S3b). The element mapping and energy dispersive X-ray (EDX) analyses of SEM images confirmed the existence of C, N, and O atoms (Figures 5 and 6). The corresponding weight percentages of C, N, and O atoms were found to be 48.3, 16.1, and 36% for OVS-A HPP, and 33.2, 13.3, and 54% for OVS-P-A HPP. Furthermore, the morphology of hybrid porous materials was further confirmed by the TEM images ( Figure S3c,d)). These images show small pores, confirming porous structure, and dark and bright patches representing amorphous characteristics in OVS-A HPP and OVS-P-A HPP.

Electrochemical Properties of OVS-A HPP and OVS-P-A HPP
The electrochemical properties were investigated in a three-electrode cell (system), using the techniques for cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) in 1 M of KOH aqueous solution (Figure 7a-d). The CV profiles of OVS-A HPP and OVS-P-A HPP were measured at different scan rates (200 to 5 mV s −1 ) and potential windows (−1 to 0 V) (Figure 7a,b). Both the samples experienced rectangular CV curves, with humps suggesting that this capacitive behavior occurred mostly from electric double-layer capacitance (EDLC) and pseudocapacitance [63]. Increasing the scan rate led to a higher specific current without changing the morphologies of the CV profiles, validating the stabilities and the efficient electron mobility [64]. The GCD curves of OVS-A HPP and OVS-P-A HPP were measured at different specific currents (0.5 to 20 A g −1 ) (Figure 7c,d). The cathodic peaks can be seen for both electrode materials in CV plots, due to the presence of heteroatoms (O and Si) in the OVS unit and electron-rich phenyl groups in the anthracene and pyrene [53,55]. The GCD curve of OVS-A HPP showed an approximately rectangular curve with a small bend, demonstrating the combined effects of pseudocapacitance and EDLC [65]. The GCD curves of OVS-P-A HPP demonstrated the traditional characteristics of a pseudocapacitance with great symmetry, suggesting a strong electrochemical performance [66]. The discharge time of OVS-P-A HPP was higher and more prominent than OVS-A HPP (Figure 7c,d), showing its comparatively high capacitance.

Electrochemical Properties of OVS-A HPP and OVS-P-A HPP
The electrochemical properties were investigated in a three-electrode cell (system), using the techniques for cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) in 1 M of KOH aqueous solution (Figure 7a-d). The CV profiles of OVS-A HPP and OVS-P-A HPP were measured at different scan rates (200 to 5 mV s −1 ) and potential windows (−1 to 0 V) (Figure 7a,b). Both the samples experienced rectangular CV curves, with humps suggesting that this capacitive behavior occurred mostly from electric doublelayer capacitance (EDLC) and pseudocapacitance [63]. Increasing the scan rate led to a higher specific current without changing the morphologies of the CV profiles, validating the stabilities and the efficient electron mobility [64]. The GCD curves of OVS-A HPP and OVS-P-A HPP were measured at different specific currents (0.5 to 20 A g −1 ) (Figure 7c,d). The cathodic peaks can be seen for both electrode materials in CV plots, due to the presence of heteroatoms (O and Si) in the OVS unit and electron-rich phenyl groups in the anthracene and pyrene [53,55]. The GCD curve of OVS-A HPP showed an approximately rectangular curve with a small bend, demonstrating the combined effects of pseudocapacitance and EDLC [65]. The GCD curves of OVS-P-A HPP demonstrated the traditional characteristics of a pseudocapacitance with great symmetry, suggesting a strong electrochemical performance [66]. The discharge time of OVS-P-A HPP was higher and more prominent than OVS-A HPP (Figure 7c,d), showing its comparatively high capacitance. The specific capacitances of OVS-A HPP and OVS-P-A HPP, calculated from GCD curves, were 120 F g −1 (calculated by using Equation (S1)) and 177 F g -1 (calculated by using Equation (S2)), respectively, at 0.5 A g −1 (Figure 8a). The difference in the specific capacitance between the OVS-A HPP and OVS-P-A HPP was very pronounced when the specific current was increased to 20 A g −1 , experiencing the values of 2 F g -1 and 2.5 F g -1 , respectively. As a result, the overall CV and GCD analysis showed that OVS-P-A HPP showed The specific capacitances of OVS-A HPP and OVS-P-A HPP, calculated from GCD curves, were 120 F g −1 (calculated by using Equation (S1)) and 177 F g -1 (calculated by using Equation (S2)), respectively, at 0.5 A g −1 (Figure 8a). The difference in the specific capacitance between the OVS-A HPP and OVS-P-A HPP was very pronounced when the specific current was increased to 20 A g −1 , experiencing the values of 2 F g -1 and 2.5 F g -1 , respectively. As a result, the overall CV and GCD analysis showed that OVS-P-A HPP showed higher electrochemical properties than OVS-A HPP. The chemical structure of OVS-P-A HPP contains pyrene groups with more electron-rich phenyl rings, allowing the electrolytes to reach the electrode surface more quickly than in the OVS-A HPP; this was responsible for its comparatively remarkable performance [67]. The Faradaic reaction between anthracene and the π-conjugated framework may also be responsible for OVS-P-A HPP's excellent performance. When the specific current was increased from 0.5 to 20 A g −1 , the specific capacitance of OVS-A HPP and OVS-P-A HPP declined, most likely because there was not enough time for ion mobility at such high specific currents [68]. The specific capacitance retention of OVS-A HPP and OVS-P-A HPP was also measured at 2000 cycles from GCD analysis (Figure 8b). The OVS-A HPP and OVS-P-A HPP exhibited excellent stability, with a specific capacitance retention of 85% and 98%, respectively. Additionally, the electrochemical performance of OVS-A HPP and OVS-P-A HPP was exceptional when compared to previously reported porous polymers and composite materials (Table S1) [53,[69][70][71][72][73][74][75]. higher electrochemical properties than OVS-A HPP. The chemical structure of OVS-P-A HPP contains pyrene groups with more electron-rich phenyl rings, allowing the electrolytes to reach the electrode surface more quickly than in the OVS-A HPP; this was responsible for its comparatively remarkable performance [67]. The Faradaic reaction between anthracene and the π-conjugated framework may also be responsible for OVS-P-A HPP's excellent performance. When the specific current was increased from 0.5 to 20 A g −1 , the specific capacitance of OVS-A HPP and OVS-P-A HPP declined, most likely because there was not enough time for ion mobility at such high specific currents [68]. The specific capacitance retention of OVS-A HPP and OVS-P-A HPP was also measured at 2000 cycles from GCD analysis (Figure 8b). The OVS-A HPP and OVS-P-A HPP exhibited excellent stability, with a specific capacitance retention of 85% and 98%, respectively. Additionally, the electrochemical performance of OVS-A HPP and OVS-P-A HPP was exceptional when compared to previously reported porous polymers and composite materials (Table S1). In addition, we examined the electrochemical properties of the OVS-A HPP and OVS-P-A HPP for a symmetric supercapacitor using coin cells ( Figure S4). The CV profiles of OVS-A HPP and OVS-P-A HPP were measured at the same scan rates and potential windows as the three electrodes ( Figure S4a,b). The CV curve for OVS-A HPP ( Figure S4a) is quite similar to the three-electrode system, but in OVS-P-A HPP (Figure S4b), the humps appeared more prominently to assist in the presence of both EDLC and pseudocapacitance. The pure triangular GCD curve was observed for OVS-A HPP, suggesting the presence of EDLC ( Figure S4c), and OVS-P-A HPP experienced a triangular curve with some In addition, we examined the electrochemical properties of the OVS-A HPP and OVS-P-A HPP for a symmetric supercapacitor using coin cells ( Figure S4). The CV profiles of OVS-A HPP and OVS-P-A HPP were measured at the same scan rates and potential windows as the three electrodes ( Figure S4a,b). The CV curve for OVS-A HPP ( Figure S4a) is quite similar to the three-electrode system, but in OVS-P-A HPP (Figure S4b), the humps appeared more prominently to assist in the presence of both EDLC and pseudocapacitance. The pure triangular GCD curve was observed for OVS-A HPP, suggesting the presence of EDLC ( Figure S4c), and OVS-P-A HPP experienced a triangular curve with some bends demonstrating EDLC and a pseudocapacitive response ( Figure S4d). The specific capacity was observed as 33 F g −1 and 80 F g −1 for OVS-A HPP and OVS-P-A at 0.5 A g −1 , respectively. Therefore, two and three electrodes revealed the significant electrochemical performance of OVS-A HPP and OVS-P-A HPP. Based on the two-electrode system, the OVS-P-A HPP had a better energy density (40 Wh Kg −1 ) than the OVS-A HPP (16 Wh Kg −1 ) ( Figure S5).

Synthesis of 1,3,6,8-Tetrabromopyrene (P-Br 4 )
Pyrene (6.00 g, 30 mmol), Br 2 (12 mL), and C 6 H 5 NO 2 (200 mL) were added to a twoneck flask and heated at 120 • C in an N 2 environment for 24 h; after that, the yellow solid (P-Br 4 , 91%) was filtered and washed by EtOH and dried under reduced pressure before it was used in the reaction. The NMR data of P-Br 4 were not provided in this work due to its poor solubility in all organic solvents.

Conclusions
Two different hybrid porous polymers of OVS-A HPP and OVS-P-A HPP were successfully synthesized through the heck reaction of OVS with anthracene and pyrene/anthracene. N 2 isothermal profiles showed the presence of micro and mesoporous properties in them with BET surfaces of 433 m 2 g −1 and 98 m 2 g −1 for OVS-A HPP and OVS-P-A HPP, respectively. The TGA analysis revealed that OVS-A HPP experienced a higher thermal stability and char yield (579 • C and 83 wt%) than OVS-P-A HPP (377 o C and 73 wt%) due to the higher cross-linking density of anthracene with OVS. Furthermore, the specific capacitance of OVS-A HPP and OVS-P-A HPP was 120 F g −1 and 177 F g −1 , respectively. The electrochemical analysis demonstrated that OVS-P-A HPP exhibited higher super-capacitive performance than OVS-A HPP and the other reported porous polymer materials.

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