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Article

Rational Fabrication of Polyhedral Oligomeric Silsesquioxane-Based Porous Organic Polymers Sustainably Used for Selective CO2 Adsorption

by
Tiantian Li
1,
Guodong Kang
2,
Mengqi Liu
2,
Congcong Sun
2,
Jie Li
3,
Yang Meng
4 and
Dingming Xue
2,*
1
School of Chemical Engineering and Technology, Xuzhou College of Industrial Technology, Xuzhou 221140, China
2
Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, 8 Jiangwangmiao Street, Nanjing 210042, China
3
Institute of Food Science and Technology, Fujian Academy of Agricultural Sciences, Fuzhou 350003, China
4
Ningbo Key Laboratory of Urban Environmental Pollution Control, CAS Haixi Industrial Technology Innovation Center in Beilun, Ningbo 315830, China
*
Author to whom correspondence should be addressed.
Processes 2024, 12(11), 2604; https://doi.org/10.3390/pr12112604
Submission received: 23 October 2024 / Revised: 15 November 2024 / Accepted: 18 November 2024 / Published: 20 November 2024
(This article belongs to the Special Issue Recent Advances in Carbon Capture, Utilisation and Storage Technologies)
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Abstract

:
Different types of porous materials have been developed for the efficient separation of CO2 from mixtures of gases. Nevertheless, the most porous materials cannot be used for extensive industrial applications due to their non-negligible disadvantages, such as complex synthesis routes, expensive monomers, and/or costly catalysts. Therefore, a strategy for fabricating a series of polyhedral oligomeric silsesquioxane (POSS)-based porous organic polymer materials (PBPOPs) was developed through the simple condensation reaction of octaphenylsilsesquioxane and different bromine-containing monomers. It was found that PBPOP-2 exhibits the best CO2 adsorption amount of 41 cm3·g−1 at 273 K and 760 mmHg based on the accessible specific surface area, large pore volumes, and accessible pore sizes. Furthermore, PBPOP-2 exhibits efficient CO2/N2 selectivity and complete regeneration under mild conditions, which demonstrates the potential for the selective separation of CO2 from gas mixtures. This work provides a new route to developing POSS-based POPs for CO2-capture applications.

1. Introduction

At present, one of the important causes of the greenhouse effect is the excessive emission of CO2 as a result of human life and production activities [1,2,3]. Carbon capture and storage technology is an efficient means for reducing CO2 emissions [4,5]. Among the traditional methods of CO2 capture, organic amine solutions, such as monoethanolamine [6], diethanolamine [7], diisopropanolamine [8], and N-methyldiethanolamine [9], are effective for chemical absorption. Although the CO2 is effectively removed, organic amine solutions have disadvantages such as high toxicity, strong corrosiveness, high volatility, and high energy consumption during regeneration operations. As an alternative method, adsorption has become a research focus due to its advantages of easy operation, non-corrosion, and easy regeneration, and has shown great practicality and broad market prospects. So far, various types of porous materials have been prepared, including activated carbon [10], zeolites [11], mesoporous silica materials [12], metal oxide materials [13], porous aromatic frameworks (PAFs) [14,15], metal–organic frameworks (MOFs) [16,17], covalent organic frameworks (COFs) [18,19], porous organic polymers (POPs) [5,20], etc., for CO2 separation from mixed gases, i.e., biogas and natural gas, in order to achieve an enhanced performance during CO2 capture.
The results in the literature demonstrate that MOFs are effective at CO2 capture as they benefit from a large specific surface area and plentiful pores. Nevertheless, most of the known MOFs originate from high-priced raw monomers, require complex synthesis routes with the use of expensive catalysts, and are easily broken down in harsh environments, such as high-temperature, moist, acidic, and alkaline conditions [17,21,22]. As porous solid materials, POPs have attracted widespread attention from researchers because of their large specific surface area, developed pore structure, flexible topology, and adjustable functional properties [5,23,24]. Many POPs have shown broad application potential in different fields, including gas adsorption and separation, electrocatalysis, sensing, heterogeneous catalysis, and drug release [25,26,27,28]. Against the backdrop of the low-carbon and emission-reduction trends, a large number of research results and related reports on the preparation of POPs and their application in CO2 adsorption and capture emerge every year.
Researchers have reported two Yttrium metal–organic frameworks (MOFs), SNNU-324 and SNNU-325, which were designed using a topology-guided strategy with 1,3,5-tris(4-carboxyphenyl) benzene (BTB) and 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (TATB) as tritopic linkers and [Y3(OH)2(H2O)4(COO)8] and [Y4O2(H2O)4(COO)8] clusters as secondary building units (SBUs), respectively [29]. SNNU-324 exhibited a good CO2/C2 hydrocarbon performance in CH4 separation, with a high specific surface area of 1395 m2·g−1 and a good CO2 uptake of 53 cm3·g−1. However, this approach has its own drawbacks, including a long synthesis time (5 days) and the need for the catalyst Sc(NO3)3·6H2O, resulting in high costs for sorbent preparation. In these works, a large specific surface area and a high CO2 adsorption capacity were achieved. However, high-priced raw materials, complex synthesis methods, and the usage of expensive catalysts all limit the further application of these adsorbents.
In our study, we were able to design and prepare porous polymer materials with the preferred simple and unexpensive monomers. Polyhedral oligomeric silsesquioxane (POSS) materials, with a cage structure size of 1–3 nm, have attracted much attention from researchers. The inorganic framework core is mainly formed by Si–O bonds and enveloped by organic groups (such as hydrogen atoms, alkyl groups, alkenyl groups, amino groups, hydroxyl groups, and other groups), which provide more possibilities for developing novel and efficient adsorbents. For example, the PMOP-1 network, which was synthesized by the crosslinking of octaphenylsilsesquioxane and p-dimethoxybenzene, resulted in a large surface area (up to 806 m2·g−1) and high CO2 adsorption capacities of 57 cm3·g−1 [30]. Nevertheless, the cost-effective Friedel–Crafts reaction cannot proceed without an effective catalyst, which is the obstacle to the further scaling up of applications of POPs. In other words, improvement in the synthesis routes without catalysts remains a significant challenge in the design and preparation of POPs.
In the present study, a series of POSS-based porous organic polymer materials (PBPOPs) were obtained using a one-step, straightforward condensation reaction of octaphenylsilsesquioxane and different bromine-containing monomers (see Scheme 1). Different types of monomers were used in this work, including 1,4-bis(bromomethyl)benzene, 4,4-bis(bromomethyl)biphenyl, and 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, respectively, and their corresponding organic polymers were named PBPOP-1, PBPOP-2, and PBPOP-3. The characteristic results in this work demonstrate that these materials have efficient CO2/N2 selectivity. More interestingly, PBPOP-2 exhibits the best CO2 adsorption capacity of 41 cm3·g−1 at 273 K and 760 mm Hg. In addition, it exhibits a complete regeneration ability under mild conditions, and its adsorption activity can be well-maintained after six cycles.

2. Materials and Methods

2.1. Material Synthesis

The commercial reagents of octaphenylsilsesquioxane, α,α’-dibromo-p-xylene, 4,4-bis(bromomethyl)biphenyl, 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, 1,2-dichloroethane, and ethanol were purchased from Adamas-beta, Shanghai, China, and all the reagents were directly used without any further treatment. The deionized water was obtained from Wahaha Group Co., Ltd., Hangzhou, China.
PBPOPs are generated by the reaction of two monomers in the absence of catalysts. As shown in Scheme 1, octaphenylsilsesquioxane (1 mmol) and α,α’-dibromo-p-xylene (8 mmol) were dissolved in 1,2-dichloroethane (60 mL), and then the mixture was heated at 343 K for 6 h with continuous stirring. After the reaction, the filter cake was washed with ethanol/deionized water three times. After further filtration and drying, the obtained powder samples were named PBPOP-1 (yield 88.4%). PBPOP-2 (yield 84.6%) and PBPOP-3 (yield 80.8%) were prepared successfully via similar synthesis processes corresponding to 4,4-bis(bromomethyl)biphenyl and 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene, respectively. All PBPOPs can be reproduced through the above processes.

2.2. Characterization

The Fourier transform infrared (FTIR) spectra were generated on a Nicolet iS10 spectrometer (Thermofisher, Waltham, MA, USA). The samples were mixed homogenously with 150-times potassium bromide, and the mixture was compressed and tested for 32 scans with a wavenumber from 4000 cm−1 to 650 cm−1. Thermogravimetry (TG) analyses were performed with a TGA209F1 apparatus (Netzsch, Waldkraiburg, Germany) so as to obtain the thermal stability. As the reaction chamber was purged by high-purity nitrogen (99.999%), the samples were heated from room temperature to 1073 K at a steady rate of 10 K·min−1. The X-ray powder diffraction (XRPD) patterns were recorded by the Bruker D8 Advance diffractometer (Bruker, Billerica, MA, USA). The detailed experimental conditions included the 2θ range of 5–80, the step size of 0.02°, and the scan rate of 1°·min−1. High-resolution transmission electron microscope (HRTEM) images were taken using an FEI Talos 200X (Thermo Scientific, Waltham, MA, USA), while scanning electron microscope (SEM) images were taken using a Zeiss Gemini SEM 300 (Zeiss, Oberkochen, Germany). The N2 adsorption–desorption isotherms were charted with a BSD-660 (BSD, Beijing, China). The samples were evacuated at 393 K for 1 h before the gas adsorption/desorption tests.

2.3. Adsorption Tests

The CO2, CH4, and N2 (pure, 99.999%) static adsorption of the samples was tested on the BSD-660, with the test conditions set to 273 K, 298 K, and 0–760 mmHg. The samples were pretreated at 393 K for 0.5 h before the CO2, CH4, and N2 (pure, 99.999%) static adsorption tests. It should be noted that all the CO2, CH4, and N2 static adsorption levels of the samples were tested three times, and the results were almost exactly the same. In order to illustrate the interaction between the gas molecules and adsorbents, the isosteric heats of adsorption (Qst) were calculated through the Clausius–Clapeyron equation. Based on the static gas adsorption experiments, the dual Langmuir (DL) model was employed to fit the adsorption isotherms, to evaluate the adsorption selectivity of the PBPOPs. The ideal adsorption solution theory (IAST) was used to predict the selectivity of CO2 over N2 and CH4. The IAST was defined as (xi/yj)/(xj/yi), in which xi and yi (xj and yj) were the molar fractions of component 1 (component 2) in the adsorbed and bulk phases, respectively.
Dynamic breakthrough experiments: the mixed gas with 15% CO2 and 85% N2 was fed into the fixed bed of PBPOPs, with the rate of 3 mL·min−1 at 273 K and 760 mmHg. The fixed bed was composed of a special glass tube and approximately 0.5 g samples, which were submerged in an ice water bath. Automated gas chromatography was adopted to determine the exact CO2/N2 composition automatically at the outlet every 30 s.

3. Results and Discussion

3.1. Characterization

Figure 1A,B show the FTIR spectra of the PBPOPs and the monomers. Clearly, the spectra of three PBPOPs are largely the same. The vibration peak at around 700 cm−1 of –C–Br– resulting from the bromine-containing monomers is weakened, which means –C–Br– is broken during the reaction. The vibration peak of –CH2–, linking the POSS and bromine-containing monomers, can clearly be observed at 2852 cm−1 and 2971 cm−1, which indicates that the bromine-containing monomer is successfully integrated into the skeleton of the PBPOPs. In addition, the Si–O–Si vibration peak is clearly recognizable at 1120 cm−1, which is the characteristic peak of POSS. Thus, these results indicate that PBPOPs were successfully prepared through a simple, one-step nucleophilic substitution reaction. Figure 1C shows the XRD patterns of PBPOPs. A large package peak can clearly be observed at 20°, and a slightly undulating package peak at 42°. The two peaks indicate the amorphous nature of PBPOPs, which are similar to the adsorbents reported in the literature [30,31,32,33].
The TG curves of PBPOPs are presented in Figure 1D, where the three PBPOPs show different weight loss stages. The slight decrease before 150 °C represents the removal of partially adsorbed water and light elements from the PBPOPs. PBPOP-1 remains largely unchanged from 200 to 400 °C, then decreases rapidly to 25% when the temperature increases to 600 °C, and remains unchanged at the high temperature (>600 °C). PBPOP-2 and PBPOP-3 both show a total weight residual of nearly 40%, which is higher than that of PBPOP-1. As the temperature increases from 200 to 800 °C, PBPOP-3 decreases steadily, at a uniform rate. In contrast, PBPOP-2 decreases slowly from 200 to 450 °C, and then it decreases to 42% at a slightly faster rate. This result is higher than that of the adsorbents reported in the literature, such as SNNU-325 (37%) [29], noria (13%) [34], and MOF-205-NH2 (10.2%) [35]. Overall, these results show that PBPOPs synthesized by different simple monomers have different structures, which lead to the large difference in thermal stability. In this case, PBPOP-2 shows the best thermal stability and the least weight loss, which is beneficial for its performance in potential industrial applications.
As shown in Figure 2A, the pore structures of the three PBPOPs were studied in detail via N2 adsorption–desorption experiments at 77 K. Clearly, PBPOPs showed a good pore structure, and the isotherms are recognizable as the IV type. Interestingly, in the low-relative-pressure region ranging from 0 to 0.05, the N2 adsorption capacities of these PBPOPs all have clear sharp increases, which indicate a good microporous structure of PBPOPs. Among them, PBPOP-1 has the lowest N2 adsorption capacity, while PBPOP-2 has the highest, indicating that the microporous structure of PBPOP-2 is more abundant than those of PBPOP-1 and PBPOP-3. With the increase in relative pressure, the adsorption isotherm of PBPOPs gradually tends to equilibrium. Within the relative pressure range of 0.5 to 1, a visible hysteresis loopback appears in the isotherms, indicating that PBPOPs have mesopores and macropores in addition to their abundant micropores. These results illustrate that PBPOPs were prepared successfully from two simple monomers via a one-step reaction without any catalysts. It is indicated that the pore structure of PBPOPs is largely determined by the different introduced bromine-containing substances.
The calculated specific surface areas and pore volumes of PBPOPs are listed in Table 1. PBPOP-2 exhibits the highest specific surface area, of 593 m2·g−1, which is higher than those of PBPOP-1 (279 m2·g−1) and PBPOP-3 (406 m2·g−1). This result is consistent with the previous analysis of N2 adsorption–desorption isotherms at 77 K. PBPOP-2 has the largest total pore volume, of 0.45 cm3·g−1, which is in accordance with the larger specific surface area than those of PBPOP-1 (0.27 cm3·g−1) and PBPOP-3 (0.37 cm3·g−1).
The corresponding micropore size distribution is listed in Figure 2B. It can be seen that all PBPOPs are conducive to the gas molecules’ immobilization because of the abundant micropores. The micropores of PBPOP-1 are not protruding, and the distribution ranging from 0.5 nm to 1.5 nm is random. In contrast, PBPOP-2 and PBPOP-3 show more plentiful pore structures. PBPOP-3 shows obviously enriched micropores, which are located at around 0.7 nm. Simultaneously, the micropores of PBPOP-2 are the most developed, and the pore sizes are mainly distributed around 0.5 nm. These results indicate a great influence of the introduction of different bromine-containing monomers on the pore structure of PBPOPs, which is in accordance with the thermal stability. According to the previous study, micropores of 0.5–1.0 nm are beneficial for the transport and adsorption of gas molecules [36]. In this case, the prepared PBPOPs seem to have good potential in gas separation and storage based on their abundant pore structures. Figure 2C–E show the irregular block surface morphologies of PBPOPs via SEM images, all revealing staggered channels and pores. In Figure 2F, the representative sample, PBPOP-2, displays a large number of wormhole-like pore structures, which should be beneficial to gas adsorption applications.

3.2. Gas Adsorption Performance

The adsorption isotherms of three PBPOPs for pure single-component CO2 at 273 K are presented in Figure 3A. It can be noted that the three PBPOPs all show a good CO2 adsorption capacity, which is mainly related to their abundant pore structures, especially the microporous structures. The adsorbed CO2 amounts of the three PBPOPs exhibit a stable and slowly increasing tendency, along with the increase in the absolute pressure from 0 to 760 mmHg. PBPOP-1 exhibits a strong CO2 adsorption capacity of 31 cm3·g−1 because of its specific surface area of 279 m2·g−1 and total volume of 0.27 cm3·g−1. Generally speaking, the CO2 adsorption capacity of the adsorbents always increases when there are more accessible pores and a larger specific surface area, which are beneficial for the CO2 molecules’ transmission and anchoring. Consequently, PBPOP-2 achieves the highest CO2 adsorption capacity, of 41 cm3·g−1, mainly attributed to its large specific surface area of 593 m2·g−1 and total pore volume of 0.45 cm3·g−1. As listed in Table 2, PBPOP-2 shows a superior CO2 adsorption capacity compared to some reported adsorbents at 273 K and 760 mmHg, such as noria (39 cm3·g−1) [34], A5 zeolite (30 cm3·g−1) [37], MOF-205-NH2 [35], ([Ni6(OH)4(BTB)8/3(H2O)6]·4H2O·9DMF)n (1) [38], Tt-POP-3 (34 cm3·g−1) [32], COP-190L (39 cm3·g−1) [39], HRN4 (31 cm3·g−1) [40], CXF1-OMe (33.6 cm3·g−1) [41], and BoxPOP-2 (34.7 cm3·g−1) [42]. However, it should be noted that the CO2 adsorption capacity of 24 cm3·g−1 for PBPOP-3 is lower than that of PBPOP-1, although the specific surface area (406 m2·g−1) and total pore volume (0.37 cm3·g−1) of PBPOP-3 are larger. This result indicates that the CO2 molecules cannot be transported or locked into the pore structure of PBPOP-3. Thus, the larger specific surface area and total pore volume do not necessarily result in a higher gas adsorption capacity. The lower CO2 adsorption capacity of PBPOP-3 may be attributed to its inaccessible pores, which are ineffective at immobilizing CO2 molecules.
As shown in Figure 3B–D, the three PBPOPs present two trends. Firstly, the CO2 adsorption capacity of PBPOPs is significantly higher than those of CH4 and N2 at the same pressure and temperature. For example, at 273 K and 760 mmHg, the adsorption capacities of PBPOP-2 for CO2, CH4, and N2 are 41 cm3·g−1, 13 cm3·g−1, and 1.3 cm3·g−1, respectively. In addition, the gas adsorption capacities of PBPOPs decrease when the temperature increases from 273 K t to 298 K, such as the adsorption capacities of PBPOP-2 for CO2, CH4, and N2, which decrease to 26 cm3·g−1, 8 cm3·g−1, and 0.8 cm3·g−1, respectively. The high adsorption capacity of PBPOP-2 is mainly related to it having the largest specific surface area and abundant accessible micropores. The micropore size of PBPOP-2 is mainly around 0.5 nm, which is beneficial for the entry and adsorption of CO2 molecules. Based on these results, PBPOP-2 achieves a high CO2 adsorption capacity and low adsorption capacities of CH4 and N2.Thus, it can be applied for selective adsorption and separation applications in natural gas and flue gas treatment.
In order to further evaluate the adsorption performance of PBPOPs for CO2, CH4, and N2, the static saturated adsorption isotherms were fitted through the theoretical DL model. Table S1 lists the values of the four parameters and the fitting correlation coefficient (R2) determined through a nonlinear regression equation. The DL model was appropriate and the fitting results reliable, which we determined as all R2 values were greater than 0.99.
The IAST model was employed to estimate the selectivity of CO2/N2. All PBPOPs exhibited good adsorption selectivity of CO2 over N2 at 273 K (see Figure 4A). At 0.1 bar, the CO2/N2 selectivity of PBPOP-2 reached 9, which was higher than those of PBPOP-1 (7.4) and PBPOP-3 (5.3). In addition, the coordination of the specific surface area and micropore structure affected the selectivity of CO2/N2. Among these sorbents, PBPOP-3 exhibited the lowest CO2 capture performance, of 24 cm3·g−1, with the middle SBET (406 m2 g−1) and the worst pore structure. Meanwhile, PBPOP-2 showed the highest CO2 uptake, of 41 cm3·g−1, the largest SBET of 593 m2 g−1, and a large number of pores, and PBPOP-1 stayed in the middle, with a 31 cm3·g−1 CO2 uptake and the lowest SBET, of 279 m2 g−1. These results clearly correspond to the order of the selectivity of CO2/N2 (PBPOP-2 > PBPOP-1 > PBPOP-3). This selectivity result is lower than that of certain reported adsorbents, such as noria (24 at 273 K and 760 mmHg) [34] and Tt-POP-1 (30 at 273 K and 760 mmHg) [32], but larger than that of MOF-205-OBn (6.5 at 273 K and 76 mmHg) [35]. The results indicate that more investigation is needed into the industrial application of PBPOPs.
In parallel, theoretical calculation in the literature reveals powerful heat-generating effects from Van der Waals interaction between the captured CO2 and the pores of the adsorbents. When the pore diameter decreases from 2 nm to 0.5 nm, the calculated adsorption heat values range from 18.9 kJ mol−1 to 29.6 kJ mol−1 [36]. As presented in Figure 4B, the Qst value of PBPOP-2 is around 20-25 kJ mol−1, showing that Qst results from the CO2 capacity in the micropore structure of PBPOP-2. Meanwhile, the Qst values of PBPOP-1 (from 37.5 kJ mol−1 to 27.5 kJ mol−1) and PBPOP-3 (from 43 kJ mol−1 to 21 kJ mol−1) are higher than that of PBPOP-2 at a certain adsorption capacity, which can be related to the improved micropore structure of PBPOP-2. Compared to the poor micropores of PBPOP-1 and PBPOP-3, the highly developed micropore structure of PBPOP-2 provides it with better CO2 adsorption. As such, the efficient improvement of CO2 adsorption originates from the specific surface area, pore volume, and appropriate micropore size of PBPOPs.
In order to estimate the selective adsorption performance of PBPOPs in PSA, dynamic breakthrough experiments were performed (see Figure 4C and Figure S1). Taking PBPOP-2 as an example, it is clear to observe that N2 is the first component to break through the fixed bed, indicating its poor adsorption capacity of N2. Meanwhile, CO2 breaks through the fixed bed of PBPOP-2 at ca. 300 s, taking quite a bit longer than N2. Interestingly, the breakthrough times of CO2 with PBPOP-1 and PBPOP-3 are ca. 180 s and ca. 140 s, which are both shorter than that of PBPOP-2. This indicates the good CO2 adsorption capacity of PBPOP-2 in this series of porous organic polymers.
In industrial applications, the regeneration stage of adsorbents normally is seen as the most critical step of CO2 capture. In laboratory conditions, using a method of in situ regeneration is a popular approach to estimate the regeneration performance of porous materials. Because of its good CO2 adsorption capacity, PBPOP-2 was mainly studied in this work, and the adsorption/desorption operations for PBPOP-2 were performed for six cycles (Figure 4D), revealing a stable CO2 adsorption capacity of around 41 cm3·g−1. Therefore, PBPOP-2 shows an excellent CO2 adsorption regeneration performance. However, it should be noted that the CO2 adsorption performance of PBPOPs decreases sharply at 323 K compared with that at 273 K. PBPOP-2 shows only 10 cm3·g−1, while PBPOP-1 and PBPOP-3 adsorb CO2 of 6.3 cm3·g−1 and 5.5 cm3·g−1, respectively, which are certainly unsatisfactory for industrial scale-up applications.

4. Conclusions

In this work, a series of PBPOPs were designed and synthesized via a straightforward, one-step condensation reaction between octaphenylsilsesquioxane and different bromine-containing monomers. Among these sorbents, a strong CO2 adsorption capacity of 41 cm3 g−1 and CO2/N2 selectivity of 9 were observed for PBPOP-2, which benefits from a substantial surface area, developed micropore structure, and well-suited micropore size. In addition, these adsorbents exhibited a strong regeneration performance and maintained adsorption activity after six cycles. Therefore, we propose that these porous organic polymer sorbents have potential in CO2 adsorption for industrial applications. Nevertheless, it should be considered that the use of bromine (Br) poses challenges concerning the environmental impact, and the low adsorption performance is unsatisfactory for industrial scale-up applications.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/pr12112604/s1. Table S1. Fitting parameters of adsorption isotherms of PBPOPs; Figure S1. Dynamic breakthrough curves of (A) PBPOP-1 and (B) PBPOP-3 for the CO2/N2 (15:85/v:v) mixture. Figure S2. CO2 adsorption isotherms of PBPOPs at 323 K.

Author Contributions

Conceptualization, D.X.; methodology, T.L., G.K., M.L., C.S. and J.L.; software, G.K., M.L., J.L. and Y.M.; validation, D.X.; writing—original draft preparation, T.L., G.K. and C.S.; writing—review and editing, D.X. and Y.M.; funding acquisition, T.L., Y.M. and D.X. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the High-level Talent Initiation Program of Xuzhou College of Industrial Technology (XGY2022EG03), the Central Public-interest Scientific Institution Basal Research Fund (GYZX240406), the Ningbo International Science & Technology Cooperation Program (2023H005), and the Ningbo Natural Science Foundation (2023J366).

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Processes 12 02604 sch001
Scheme 1. Schematic illustration of the synthesis route of PBPOP-1.
Scheme 1. Schematic illustration of the synthesis route of PBPOP-1.
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Processes 12 02604 g001
Figure 1. FT-IR spectra of (A) the PBPOPs and (B) the monomers; (C) XRD patterns and (D) TG curves of the PBPOPs.
Figure 1. FT-IR spectra of (A) the PBPOPs and (B) the monomers; (C) XRD patterns and (D) TG curves of the PBPOPs.
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Figure 2. (A) N2 adsorption–desorption isotherms at 77 K and (B) corresponding pore size distributions of PBPOPs. SEM images of (C) PBPOP-1, (D) PBPOP-2, and (E) PBPOP-3. (F) TEM image of PBPOP-2.
Figure 2. (A) N2 adsorption–desorption isotherms at 77 K and (B) corresponding pore size distributions of PBPOPs. SEM images of (C) PBPOP-1, (D) PBPOP-2, and (E) PBPOP-3. (F) TEM image of PBPOP-2.
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Figure 3. (A) CO2 adsorption isotherms of PBPOPs at 273 K. CO2, CH4, and N2 adsorption isotherms of (B) PBPOP-1, (C) PBPOP-2, and (D) PBPOP-3 at 273 K and 298 K.
Figure 3. (A) CO2 adsorption isotherms of PBPOPs at 273 K. CO2, CH4, and N2 adsorption isotherms of (B) PBPOP-1, (C) PBPOP-2, and (D) PBPOP-3 at 273 K and 298 K.
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Figure 4. (A) IAST selectivity of CO2/N2 (15:85/v:v) on the PBPOPs at 273 K. (B) CO2 isosteric heat of adsorption of the PBPOPs. (C) Dynamic breakthrough curves of PBPOP-2 for the CO2/N2 (15: 85/v:v) mixture. (D) Adsorption cycles of CO2 over PBPOP-2 at 273 K and 760 mmHg.
Figure 4. (A) IAST selectivity of CO2/N2 (15:85/v:v) on the PBPOPs at 273 K. (B) CO2 isosteric heat of adsorption of the PBPOPs. (C) Dynamic breakthrough curves of PBPOP-2 for the CO2/N2 (15: 85/v:v) mixture. (D) Adsorption cycles of CO2 over PBPOP-2 at 273 K and 760 mmHg.
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Table 1. Textural parameters of PBPOPs.
Table 1. Textural parameters of PBPOPs.
SampleSBET
(m2·g−1)		Vtotal
(cm3·g−1)		Vmicro
(cm3·g−1)		Vmeso
(cm3·g−1)
PBPOP-25930.450.270.28
PBPOP-34060.370.220.15
PBPOP-12790.270.140.13
Table 2. CO2 uptake levels of certain adsorbents at 273 K and 760 mmHg.
Table 2. CO2 uptake levels of certain adsorbents at 273 K and 760 mmHg.
SamplesSBET (m2·g−1)Q (cm3·g−1)Ref.
PBPOP-259341This work
SNNU-324139553[29]
Noria21839[34]
A5 Zeolite17930[37]
MOF-205-NH2433013[35]
([Ni6(OH)4(BTB)8/3(H2O)6]·4H2O·9DMF)n (1)46832[38]
Tt-POP-397434[32]
COP-190L28439[39]
HRN415631[40]
CXF1-OMe62633.6[41]
BoxPOP-123128[42]
POSS-TPE74144[33]
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Li, T.; Kang, G.; Liu, M.; Sun, C.; Li, J.; Meng, Y.; Xue, D. Rational Fabrication of Polyhedral Oligomeric Silsesquioxane-Based Porous Organic Polymers Sustainably Used for Selective CO2 Adsorption. Processes 2024, 12, 2604. https://doi.org/10.3390/pr12112604

AMA Style

Li T, Kang G, Liu M, Sun C, Li J, Meng Y, Xue D. Rational Fabrication of Polyhedral Oligomeric Silsesquioxane-Based Porous Organic Polymers Sustainably Used for Selective CO2 Adsorption. Processes. 2024; 12(11):2604. https://doi.org/10.3390/pr12112604

Chicago/Turabian Style

Li, Tiantian, Guodong Kang, Mengqi Liu, Congcong Sun, Jie Li, Yang Meng, and Dingming Xue. 2024. "Rational Fabrication of Polyhedral Oligomeric Silsesquioxane-Based Porous Organic Polymers Sustainably Used for Selective CO2 Adsorption" Processes 12, no. 11: 2604. https://doi.org/10.3390/pr12112604

APA Style

Li, T., Kang, G., Liu, M., Sun, C., Li, J., Meng, Y., & Xue, D. (2024). Rational Fabrication of Polyhedral Oligomeric Silsesquioxane-Based Porous Organic Polymers Sustainably Used for Selective CO2 Adsorption. Processes, 12(11), 2604. https://doi.org/10.3390/pr12112604

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