Facile Preparation of Triphenylamine-Based Nanoporous Organic Polymers for Adsorption/Separation of C₁–C₃ Hydrocarbons and CO₂ in Natural Gas

Abstract

The development of porous organic polymers with high gas adsorption and separation performances by a facile preparation process has progressively addressed the urgent demand for cost-effective adsorbents employed in energy-efficient purification and recovery processes. However, these polymeric materials are still poorly developed for the practical adsorption and separation of light C1–C3 hydrocarbon components, such as methane (CH4), ethane (C2H6), and propane (C3H8), from natural gas under ambient conditions. The present work addresses this issue by reporting the facile preparation of two triphenylamine-based nanoporous organic polymers (ANOPs), ANOP-M and ANOP-A, via acid-catalyzed Friedel–Crafts hydroxyalkylation polymerization using commercially available triphenylamine with tetrakis­(4-formylphenyl)­methane and 1,3,5,7-tetrakis­(4′-formylphenyl)­adamantane monomers, respectively. The specific surface areas of the ANOPs vary from 1052 to 1272 m2/g, with average pore sizes of 1.36 nm. Furthermore, the ANOP networks are demonstrated to be highly interconnected. Interestingly, the ANOPs have different adsorption capacities toward different C1–C3 hydrocarbons (CH4, C2H6, and C3H8) and CO2 molecules, and ANOP-M shows the highest uptake of C3H8 (97.9 cm3/g) and C2H6 (64.6 cm3/g) among these gas molecules at 298 K and 1 bar. Analyses reveal that these differences depend greatly upon the physical parameters of the gas molecules (e.g., polarizability, critical temperature, and molecular size) and the porosity parameters of the ANOPs, as well as the affinity between the gases and the polymer skeleton. The adsorption selectivities of the ANOPs in conjunction with C3H8/CH4, C2H6/CH4, C3H8/C2H6, C3H8/CO2, C2H6/CO2, and CO2/CH4 gas mixtures also differ significantly and exhibit values of 151–164, 17.5–17.8, 6.16–6.43, 14.2–15.1, 2.93–3.17, and 4.35–4.70, respectively. Accordingly, the facile preparation and excellent light hydrocarbon adsorption and separation properties of the ANOPs make these materials highly promising for applications involving the adsorption/separation of C1–C3 light hydrocarbons and CO2 from natural gas under ambient conditions.

Friedel–Crafts Synthesis of Carbazole-Based Hierarchical Nanoporous Organic Polymers for Adsorption of Ethane, Carbon Dioxide, and Methane

“…Furthermore, we observed that CNOP-2 showed higher capacities and lower Q st for C 2 H 6 , CO 2 , and CH 4 than CNOP-1, which is ascribed to the higher BET surface area and larger pore sizes of CNOP-2. This phenomenon has also been reported in previously published works. ,,, …”

Construction of a Carbazole-Based Nanoporous Organic Polymer via an AB2 Monomer for Adsorption/Separation of C1–C3 Alkanes and CO2

“…The C 3 H 8 , C 2 H 6 , CO 2 , and CH 4 adsorption uptakes of CNOP-5 are listed in Table S1. CNOP-5 can take up C 3 H 8 and C 2 H 6 of 174.1 and 115.4 cm 3 /g, respectively, at 273 K and 101 kPa, surpassing the previously reported NOPs such as CNOPs (76.8−99.5 and 58.2−76.4 cm 3 •g −1 ), 2 ANOPs (109.4−134.9 and 78.5−90.2 cm 3 •g −1 ), 24 and PANs (53.8− 143.2 and 44.8−108.1 cm 3 •g −1 ). 3,25,26 Because of physisorption, the four gas uptakes of CNOP-5 exhibited a downward trend with the temperature from 273 to 298 K. As displayed in Table S1, we observed C 3 H 8 and C 2 H 6 capacities of 127.0 and 82.4 cm 3 /g at 101 kPa and 298 K, respectively.…”

“…3,25,26 Because of physisorption, the four gas uptakes of CNOP-5 exhibited a downward trend with the temperature from 273 to 298 K. As displayed in Table S1, we observed C 3 H 8 and C 2 H 6 capacities of 127.0 and 82.4 cm 3 /g at 101 kPa and 298 K, respectively. These capacities can compete with the previously reported NOPs, as shown in Figure 3(c), such as CNOPs (62.7−82.1 and 47.2− 60.0 cm 3 •g −1 ), 2 ANOPs (82.4−97.9 and 57.7−64.6 cm 3 •g −1 ), 24 PANs (43.9−119.0 and 29.1−84.2 cm 3 •g −1 ), 3,25,26 and sPIs (38.8−44.8 and 27.7−35.6 cm 3 •g −1 ). 11 Simultaneously, CNOP-5 uptake 48.1 cm 3 /g CO 2 under ambient conditions, which is higher than for sPANs (21.1−24.4 cm 3 /g), 1 PMOPs (40.7−41.5 cm 3 /g), 27 ANOP-M (40.6 cm 3 /g), 24 and 3AM2CL (13.4 cm 3 /g).…”

“…These capacities can compete with the previously reported NOPs, as shown in Figure 3(c), such as CNOPs (62.7−82.1 and 47.2− 60.0 cm 3 •g −1 ), 2 ANOPs (82.4−97.9 and 57.7−64.6 cm 3 •g −1 ), 24 PANs (43.9−119.0 and 29.1−84.2 cm 3 •g −1 ), 3,25,26 and sPIs (38.8−44.8 and 27.7−35.6 cm 3 •g −1 ). 11 Simultaneously, CNOP-5 uptake 48.1 cm 3 /g CO 2 under ambient conditions, which is higher than for sPANs (21.1−24.4 cm 3 /g), 1 PMOPs (40.7−41.5 cm 3 /g), 27 ANOP-M (40.6 cm 3 /g), 24 and 3AM2CL (13.4 cm 3 /g). 28 Higher CO 2 uptake can be attributed to high-porosity and rich-polarity carbazole units.…”

A facile one-pot preparation of porphyrin-based microporous organic polymers for adsorption of carbon dioxide, ethane, and methane

“…Microporous organic polymers (MOPs) with high microporosity, excellent gas uptakes, and low isosteric heat of adsorption for CO 2 have been developed to address these shortcomings. Simultaneously, MOPs have also shown extensive applications, including the adsorption/separation of other simple gases (e.g., C 2 H 6 , CH 4 , and N 2 ), [2][3][4][5] catalysis, [6][7][8][9][10][11] sensors, [12][13][14] recovery of gold, 15,16 and water treatment. [17][18][19] Due to their excellent physicochemical properties and high porosity, more attention was focused on the design and development of MOPs to adsorb and separate simple molecular gases (such as CO 2 , C 2 H 6 , and CH 4 ) in science and industry.…”