Electron-rich Heteroatoms Research Articles

Design and synthesis of carbazole-based conjugated microporous polymers for CO2 capture

Conjugated microporous polymers (CMPs) with electron-rich heteroatoms in the skeleton have been receiving continuous attention for their huge potential in carbon dioxide (CO2) capture with high selectivity. Herein, we designed and synthesized three CMPs (MFCM-CMP, FFCM-CMP, and FFC-CMP-1) for CO2 capture. The MFCM-CMP and FFCM-CMP were obtained by the reaction between the similar carbazole- and fluorine-based building blocks and cyanuric chloride, while the FFC-CMP-1 was synthesized by self-polymerization of 9,9′-(9,9-difluoro-9H-fluorene-2,7-diyl)bis(9H-carbazole) (FFC) building blocks. The as-prepared CMPs had high specific surface areas (SABET = 688-1245 m2/g), and hierarchical porous skeletons with average pore sizes from 2.7 to 3.2 nm. Furthermore, all the CMPs exhibited excellent gas (CO2, N2, CH4) uptake capacity. Remarkably, FFCM-CMP performed the CO2, N2, and CH4 uptake for 74.5 cm3/g, 4.2 cm3/g, and 17.4 cm3/g at 273 K, 1.0 bar, and the CO2 capture selectivity could achieve 19.6 and 4.3 from CO2/N2 (15/80) and CO2/CH4 (50/50) mixture at 298 K, 1.0 bar, respectively. The gas breakthrough test carried out in CO2/N2/Ar (15/80/5) disclosed evidently that the synthesized CMPs with triazine groups exhibited outstanding CO2 capture selectivity. This work provides a new strategy for porous organic adsorbent for improving CO2 selectivity from the molecular level.

Pd(OAc)2/P–COF: A phosphine-based COF supported palladium-salt heterogeneous catalyst for Suzuki-Miyaura coupling reactions at ambient conditions

A new type of phosphine covalent organic frameworks (P-COFs) has garnered interest because of their high specific surface area and good thermal stability. These microporous materials have potential applications in gas storage, separation, heterogeneous catalysis, and other fields. Here, we present a heterogeneous catalyst consisting of a phosphine-based COF supported by palladium salt (Pd(OAc)2/P-COF) for Suzuki-Miyaura coupling reactions. The electron-rich heteroatoms (P, N) can securely anchor the active component (Pd) within the walls of P–COF. This catalyst exhibits excellent catalytic activity and cyclic stability. The coupling yield of phenylboronic acid and chlorobenzene with low activity reaches 100 % at room temperature for 3 h. After five cycles, the coupling yield of bromobenzene and phenylboronic acid remains above 93 %.

Tunable Luminescence of Nonaromatic Borate Esters.

While the majority of nonconventional luminophores consist of electron-rich heteroatoms, an emerging category with electron-deficient atoms (e. g. boron) have gained much attention. In this work, we focused on one of the most common boron-containing substances, namely bis(pinacolato)diboron (BE1) and its analogue bis(2,4-dimethylpentane-2,4-glycolato)diboron (BE2), whose empty p-orbitals of boron atoms and p-orbitals with lone pairs of oxygens form π frameworks. Both compounds are nonemissive in dilute solutions but depict remarkable photoluminescence (PL) at aggregate states, featuring aggregation-induced emission characteristics. Additionally, their PL can be easily tuned by various external factors, such as excitation wavelength, compression, and oxygen. These photophysical properties could well be explained by the clustering-triggered emission (CTE) mechanism.

Design and synthesis of thiophene containing bis-chalcone-based mesoporous polymers for volatile iodine capture

Two novel thiophene-containing bis-chalcone-based polymers poly [(1E,4E)-1,5-Di-2-thienylpenta-1,4-dien-3-one] (PTCA) and poly[(1E,4E)-2,4-dimethyl-1,5-di(thiophen-2-yl)penta-1,4-dien-3-one] (PTCM) were designed and synthesized by FeCl3 mediated oxidative coupling polymerization reaction. The formation of polymers was confirmed by FT-IR and UV-DRS analysis, and the structural and morphological characterizations were done by PXRD, SEM, TEM, TGA, CHNS, and BET analysis techniques. Owing to their mesoporous nature, and excellent thermal and chemical stability, they found significant applications in the field of environmental remediation. Regardless of their low surface area, they emerged as strong candidates for the iodine capture process due to the presence of electron-rich heteroatoms. The maximum iodine capture capacity obtained for PTCA and PTCM were 242 and 221 wt.% respectively. The kinetic study revealed that the adsorption of iodine onto the polymers fit well in the pseudo-second-order kinetic model with a correlation coefficient R2 > 0.99, pointing to the chemisorptive nature of adsorption. The polymers can be competently recycled and reused even after five cycles without a significant loss of iodine uptake. After the first cycle, the iodine release efficiency was as high as 89% and 93% for PTCA and PTCM respectively. The iodine uptake capacity of the reused polymers PTCA and PTCM was found to be 89.2% and 86.5% respectively after five successive cycles. And these materials offer the benefits of facile, low-cost, large-scale, and template-free synthesis of mesoporous polymers. This study also provides an opportunity for the design same kind of polymers with different heteroatoms and functional groups.

The flexible EDAN-based covalent organic frameworks constructed by flexible knots and 4,4′-ethylenedianiline as a linker for adsorping and fluorescence sensing iodine

In this paper, 4,4′-ethylenedianiline as a linker, flexible 2,4,6-tris(4-formylphenoxy)- 1,3,5-triazine (TPT−3−CHO) and hexa(4-formyl-phenoxy)cyclotriphosphazene (NOP−6−CHO) as knots were selected to construct the new flexible EDAN-based COFs (TEDAN and HEDAN) through Schiff base reactions of aldehyde and amine. The as-prepared flexible EDAN-based COFs have high crystallinity, sizable surface area, and thermal stability. With porous properties, abundant electron-rich heteroatoms as well as large π-conjugated network structures that can provide effective binding sites, TEDAN and HEDAN exhibit good reversible vapor-trapped iodine with the adsorption capacities of 4.64 and 2.25 g g−1, respectively. The aromatic networks of nitrogen-rich units in TEDAN provide many binding sites with guest iodine molecules than that of HEDAN, resulting in higher equilibrium uptake capacity of iodine for TEDAN. In addition, the flexible EDAN-based COFs show “turn-off” detection of non-radioactive iodine in the dispersion state with quenched constants (KSV) of 5.59 × 104 and 2.35 × 104 L mol−1. The fluorescence quenching of the flexible TEDAN-based COFs can be attributed to both the photo-induced electron transfer mechanism and the energy transfer transfer mechanism. The sensitivity of HEDAN is higher than that of TEDAN.

Design of hierarchically porous carbon frameworks for enhanced CO2 capture performance

To reduce the environmental impact of CO2, CO2 capture has become an area of research interest. Hierarchically porous materials have been certified as efficiency CO2 capture adsorbents. This work is aimed to construct hierarchically porous carbon frameworks (CPI-TPUs) with enhanced CO2 capture performance. CPI-TPUs are derived from polyimide (PI)/thermoplastic polyurethane (TPU) composite aerogels (PI-TPUs) with mesopores and macropores. Accordingly, the obtained CPI-TPU2 exhibits an improved CO2 uptake capacity (2.21 mmol/g, 298 K) compared to the pure CPI and PI-TPUs due to the synergistic effect of hierarchically pores, higher specific area and electron-rich heteroatoms. Specially, CPI-TPUs with pore volume ratio of mesopores/macropores to total pores in a range of 6–21 show high CO2 uptake performance. These CPI-TPUs with high CO2 adsorption capacities and suitable isosteric adsorption heats (Qst) are promising CO2 adsorbents.

Adsorption of heavy metal ions by thiophene containing mesoporous polymers: An experimental and theoretical study

Two novel mesoporous polymers poly [(1E,4E)-1,5-Di-2-thienylpenta-1,4-dien-3-one] (PTCA) and poly[(1E,4E)-2,4-dimethyl-1,5-di(thiophen-2-yl)penta-1,4-dien-3-one] (PTCM) having electron-rich heteroatoms (O and S) have been designed and synthesized by oxidative coupling polymerization promoted by FeCl3. Paid to their excellent physiochemical properties such as porous nature, thermal stability, chemical stability, tunable functionality, presence of electron-rich heteroatoms, etc., they are determined as a prominent candidate for heavy metal ion adsorption irrespective of their low surface area. Hence the synthesized polymers were tested for the adsorption of heavy metal ions from aqueous solutions and found to be promising in the effective removal of Zn2+ and Pb2+ ions. The maximum adsorption capacity of the polymer PTCA for Zn2+ and Pb2+ was calculated as 729.4 ​mg/g and 569.1 ​mg/g respectively, and the maximum adsorption capacity of the polymer PTCM for Zn2+ and Pb2+ was calculated as 652.7 ​mg/g and 545.1 ​mg/g respectively. The desorption study reveals that for PTCA the maximum percentage recovery of Zn2+ and Pb2+ ions was 76.9% and 79.9% respectively, and for PTCM the maximum percentage recovery of Zn2+ and Pb2+ ions was 68.5%, and 73.7% respectively. The theoretical study was conducted to support the experimental results. Also, our materials generate a breakthrough in the field of simple, economic, and template-free development of the same type of novel polymers having different functionalities.

Preparation of an electron-rich polyimide-based hypercrosslinked polymer for high-efficiency and reversible iodine capture

Effective and reversible iodine adsorption is among the most important means to solve nuclear pollution. Herein, a novel electron-rich hypercrosslinked polymer (HCP) was obtained via a simple photocycloaddition of the cinnamoyl-containing polyimide precursor. The resulting polymer showed a high specific surface area of 531 m2 g−1 and high thermal stability. Taking advantage of the high porosity, high electron-rich heteroatoms contents and π-electron conjugated backbone, the material exhibits excellent iodine capture performance, including ultrahigh iodine vapor capture (528 wt%) and iodine removal efficiency from aqueous solution. The capture behavior is consistent with the pseudo-second-order model and the spectral results indicate that the captured iodine existed in the form of polyiodide anions. Furthermore, the HCP maintained 90.76% of the uptake capacity after four cycles. This study provides a new proposal for the preparation of functional HCP as an efficient iodine absorbent to solve environmental issues.

Directional porous polyimide/polyethylene glycol composite aerogel with enhanced CO2 uptake performance

The cost of CO2 separation and energy consumption can be decreased through the use of CO2 adsorption. Due to the electron-rich heteroatoms in its network, polyimide (PI) has a remarkable affinity for CO2. Polyethylene glycol (PEG) can increase the layer spacing of polymers, so as to change the mass transfer of CO2 in it. Furthermore, the ether bond (-O-) in PEG has good affinity for CO2. In this study, PEG-1000 was introduced into PI aerogel by mild sol-gel method at low temperature, and freeze-drying was used to produce PI/PEG composite aerogels with directional pore structure. The effect of PEG-1000 content and directional pore structure of the PI/PEG composite aerogels on CO2 adsorption performance were further studied. The L-PI/PEG-4 composite aerogel, which contains 4 g PEG and is directionally frozen in liquid nitrogen, has a CO2 adsorption capacity of 16.76 cm3/g at 25°C and 1 bar. L-PI/PEG-4 aerogel also exhibits high CO2/N2 selectivity and adsorption cycle stability.

LimF is a versatile prenyltransferase for histidine-C-geranylation on diverse non-natural substrates

Prenylation plays an important role in diversifying the structure and function of secondary metabolites. Although several cyanobactin prenyltransferases have been characterized, their chemistries are mainly limited to the modification of electron-rich heteroatoms. Here we report a prenyltransferase, LimF, from Limnothrix sp. CACIAM 69d, geranylating the electron-deficient C2 atom of His imidazole. Interestingly, in addition to its native substrate, LimF also modifies diverse exotic peptides, including thioether-closed macrocycles. We have also serendipitously uncovered Tyr-O-geranylating activity as the secondary function of LimF, providing evolutional insight into the divergent repertoire of prenylated peptides produced by cyanobactin PTases. Crystallographic analysis of LimF complexed with a pentapeptide substrate and a prenyl donor analogue provides the structural basis for its His recognition and its bifunctionality. We also show the prenylation ability of LimF on various bioactive molecules containing an imidazole group, including non-amino acid small molecules, highlighting its potential as a versatile biocatalyst for chemically challenging imidazole C-geranylation.

Novel phenothiazine-based hyper-cross-linked porous polymers containing N, S double electrically rich atoms for efficient iodine capture

Novel phenothiazine-based hyper-cross-linked porous polymers (PZ-HCPs) containing N, S double electron-rich atoms were synthesized using Friedel-Crafts alkylation reaction. Nitrogen adsorption-desorption test showed that the specific surface areas (SBET) of the PZ-HCPs were between 131 m2 g−1 and 209 m2 g−1. In addition, the π-electron-conjugated structure and the presence of N and S electron-rich heteroatoms in the PZ-HCPs facilitated its high iodine capture ability in both iodine solution and iodine vapor. Meanwhile, adsorption mechanism studies showed that the adsorbed iodine in the adsorbent existed as I3– and I5– . The adsorption behavior of PZ-HCP-1:4 for iodine conformed to the pseudo-second-order (PSO) kinetic model and Freundlich isotherm model. This work supplies a strategy for synthesizing HCPs as adsorbents for the treatment of radioactive iodine in nuclear waste.

High-surface β-Ketoenamine linked covalent organic framework driving broad-spectrum solid phase microextraction on multi-polar aromatic esters

Aromatic esters have been widely used in daily life with non-ignorable dangers, such as plasticizer, flavor, and preservative. Their wide applications and corresponding hazards caused by overuse have promoted the rapid development of sensitively analytical method for effective regulation. However, the variety makes it challenging for broad-spectrum and simultaneous extraction of diverse aromatic esters from the highly complex cosmetic samples. To our delight, a covalent organic framework, named DaTp (1, 3, 5-triformylphloroglucinol-2, 6-diaminoanthracene), possessing high specific surface, excellently thermochemical stability, and abundant electron-rich heteroatoms, has been synthesized and fabricated as a competitive solid phase microextraction coating for extracting the trace analytes with diverse polarity, through the hydrophobic interaction, π-π conjugation and hydrogen bond. Herein, this self-made SPME fiber has been further coupled with gas chromatography-tandem mass spectrometry (GC-MS) to determine the multi-polar aromatic esters in cosmetics packaged with plastic. This developed analytical method showed wide liner ranges, low limits of detection, good repeatability and reproducibility. Finally, the aromatic esters in four cosmetic samples were quantified precisely with satisfactory recoveries (80.7%–118%).

Cryogenic infrared spectroscopy provides mechanistic insight into the fragmentation of phospholipid silver adducts

Tandem mass spectrometry is arguably the most important analytical tool for structure elucidation of lipids and other metabolites. By fragmenting intact lipid ions, valuable structural information such as the lipid class and fatty acyl composition are readily obtainable. The information content of a fragment spectrum can often be increased by the addition of metal cations. In particular, the use of silver ions is deeply rooted in the history of lipidomics due to their propensity to coordinate both electron-rich heteroatoms and C = C bonds in aliphatic chains. Not surprisingly, coordination of silver ions was found to enable the distinction of sn-isomers in glycerolipids by inducing reproducible intensity differences in the fragment spectra, which could, however, not be rationalized. Here, we investigate the fragmentation behaviors of silver-adducted sn- and double bond glycerophospholipid isomers by probing fragment structures using cryogenic gas-phase infrared (IR) spectroscopy. Our results confirm that neutral headgroup loss from silver-adducted glycerophospholipids leads to dioxolane-type fragments generated by intramolecular cyclization. By combining high-resolution IR spectroscopy and computational modelling of silver-adducted fragments, we offer qualitative explanations for different fragmentation behaviors of glycerophospholipid isomers. Overall, the results demonstrate that gas-phase IR spectroscopy of fragment ions can significantly contribute to our understanding of lipid dissociation mechanisms and the influence of coordinating cations.Graphical abstract

Novel gossypol–indole modification as a green corrosion inhibitor for low–carbon steel in aggressive alkaline–saline solution

The corrosion of low–carbon steel in aggressive alkaline–saline environments is a very large problem. Protecting low–carbon steel from corrosion in aggressive alkaline–saline solutions using green inhibitors is a very important task in industry. However, there are no studies related to low–carbon steel corrosion in aggressive alkaline–saline environments. Green type corrosion inhibitors are an interesting topic of research. However, currently, the studied type inhibitors are not efficient at low concentrations, and there are no studies on them in aggressive alkaline–saline environments in regard to steel corrosion. In this research work, a novel gossypol–indole modification (GIM) is introduced as a green corrosion inhibitor for low–carbon steel in an aggressive alkaline–saline environment. This inhibitor is a large, highly planar structural molecule that is more water soluble than other inhibitors. Its inhibition behavior is stable at high temperatures, and it contains a large number of electron–rich heteroatoms. All of these properties make it an excellent corrosion inhibitor. The inhibition performance of the novel gossypol–indole modification for low–carbon steel in 1 M NaOH + 1 M NaCl is fully characterized by thermodynamic, gravimetric, electrochemical frequency modulation (EFM), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), density functional theory (DFT), molecular dynamics (MD) simulations, scanning electron microscopy (SEM) and energy dispersive X–ray spectrometry (EDX) methods. The results confirm that the novel gossypol–indole modification is an excellent inhibitor, with a maximum inhibition efficiency of 96.01% at 100 mg/L and 0.112 mM. The adsorption behavior follows the Langmuir isotherm. Electrochemical studies have indicated that this modified is a mixed–type corrosion inhibitor, and the theoretical investigations correlate well with the experimental results.

Phosphine-based covalent organic framework for highly efficient iodine capture

The efficient capture of nuclear waste such as radionuclide iodine has received more worldwide attention because of the effects of radiation on biological health. Adsorption is considered to be an efficient, low-cost, and environmentally friendly method for iodine removal. Recently, a new kind of phosphine-based covalent organic frameworks (P-COFs) with flexible and nonplanar structure have attracted great attention because of their high specific surface area and good thermal stability. The existence of electron-rich heteroatoms (P, N) as well as the large π-conjugated network structure may be beneficial to the absorption of iodine. In this study, a biphenyl linked P-COF was synthesized for the capture of iodine. It shows a uniform microsphere structure with a diameter of about 1.2 μm, a large BET surface area up to 1056 m 2 g −1 , and a high thermal stability (up to 500 °C). This P-COF exhibits rapid and exceptional iodine uptake in both volatile iodine and iodine/cyclohexane solution with adsorption capacities of 6.19 g g −1 and 1.30 g g −1 , respectively, suggesting that P-COF may be a potential candidate for radioiodine capture from nuclear waste. • A phosphine-based covalent organic framework (P-COF) is developed for the capture of iodine. • P-COF exhibits rapid volatile iodine uptake with an adsorption capacity of 5.00 g g −1 within 2 h. • The equilibrium adsorption capacity of vapor iodine reaches as high as 6.19 g g −1 . • P-COF shows tremendous iodine adsorption with capacity of 1.30 g g −1 in cyclohexane solution.

Isoelectric Si Heteroatoms as Electron Traps for N2 Fixation and Activation

AbstractDoping the host materials with either electron‐rich heteroatoms or electron‐deficient heteroatoms have been applied as a straightforward and main‐stream method to modify the electronic structures and boost the electrochemical activity for various reactions, including nitrogen reduction reactions (NRR). As the third type of dopants, isoelectric heteroatoms (exemplified with Si atoms in carbon framework in this work) have been designed as highly efficient active centers for NRR. As the same group element with a different size and electronegativity to carbon support, the isoelectric Si heteroatom (Iso‐e Si) creates localized singularities with a lone orbital that can act as an electron trap for pre‐adsorbed N2 molecules through coulomb interaction and thus facilitates the following activation process for NRR. Iso‐e Si atom thus functions as a special type of metal‐free single atom‐based electrocatalyst to largely boost the faradaic efficiency of pristine carbon support for NRR by a factor of 12, giving a remarkably high turnover frequency value of 0.52 h−1, comparable to atomically dispersed transition metal‐based electrocatalysts.

N- and S-rich covalent organic framework for highly efficient removal of indigo carmine and reversible iodine capture

Abstract Organic dye containing wastewater and nuclear waste have received more worldwide attention because of the significant environmental problems and the effects of radiation on health. Adsorption is considered to be an efficient, low-cost, and environmentally friendly method for pollutant removal. In this paper, we developed a novel covalent organic framework (BTT-TAPT-COF) adsorbent which contains abundant S and N active sites as well as extended π-conjugated structure. This COF shows high crystallinity, large surface area, and thermal stability. Due to the porous feature, existence of electron-rich heteroatoms as well as the large π-conjugated network structure, BTT-TAPT-COF exhibits excellent adsorptive performance for the removal of hazardous dye indigo carmine with an adsorption capacity of 547.33 mg g−1 and rapid reversible volatile iodine uptake with an adsorption capacity of 276 wt%. After five cycles, BTT-TAPT-COF almost retains the same iodine adsorption capacity with the original adsorbent.

Tunable Surface Modification of Mesoporous Carbon Nanoparticles for Polysulfide Trapping in Lithium-Sulfur Batteries

Lithium-Sulfur (LiS) batteries are a front runner for next-generation secondary battery systems. This is partially due to the low cost, relative abundance, and environmentally benign nature of their active materials, but arguably most important is the order of magnitude increase in theoretical specific capacity of LiS cells compared to current state of the art lithium-metal oxide systems (~1,600 mAhg-1 vs ~160mAhg-1, respectively). Despite these inherent benefits, the commercialization of LiS systems has been impeded by a rapid loss of capacity upon repeated cycling due to the complexities of lithiation and delithiation at the carbon/sulfur composite cathode. During discharge, elemental sulfur is sequentially reduced to lithium sulfide following the reaction S8 + 16Li+ + 16e-→ 8Li2S, where intermediates Li2S(8-2) are formed, their length depending on depth of discharge. Long-chain lithium polysulfides (LiPS), Li2S(8-4) are highly soluble in organic electrolytes and, once solvated, will migrate to the lithium metal anode. This leads to permanent capacity loss and internal shorting via lithium polysulfide redox shuttling. To combat this limitation, extensive efforts have been focused on trapping long-chain LiPS by both: 1. physically confining them in mesoporous carbons, and 2. chemically inducing electrostatic attractions with electron rich heteroatoms on the cathode. In this work we not only aim to find synergy between these two approaches, but also investigate the potential for doubling the binding energy of electrostatic interactions by covalent tethering of long chain LiPS to the cathode surface via reversible di-sulfide bonding. Through a highly tunable one-step reaction, we functionalize mesoporous carbon surfaces with aromatic small molecules using in-situ generation of diazonium radicals. The flexibility of our approach allows for the introduction of a wide variety of surface functionality, and thus a platform to broaden our understanding of cathode/electrolyte interactions. Our current progress focuses on the spectroscopic, physical, and electrochemical characterization of a thiophenol terminated carbon. Through this work we have demonstrated not only successful modification of carbon particles, but an ability to control the density of modifier groups on the surface. In conjunction with finding an optimal concentration of surface modifiers, we investigate the role of modifiers and carbon pore size in modulating the kinetics and capacity retention of LiS cells. By optimizing pore-size and modifier concentration, we have drastically increased the cycle life of our devices, which maintain >900 mAhg-1 over 150+ cycles at 0.1C. We hypothesize that the mechanism responsible for this improvement is a reversible covalent interaction based on electrochemical measurements, which indicate a concentration-dependent shift toward solid-phase reaction pathways.

Promoting and Tuning Porosity of Flexible Ether-Linked Phthalazinone-Based Covalent Triazine Frameworks Utilizing Substitution Effect for Effective CO2 Capture.

Five porous ether-linked phthalazinone-based covalent triazine frameworks (PHCTFs) were successfully constructed via ionothermal polymerizations from flexible dicyano monomers containing asymmetric, twisted, and N-heterocyclic phthalazinone structure. All the building blocks could be easily prepared by simple and low-cost aromatic nucleophilic substitution reactions, showing the large-scale application potential of thermal stable phthalazinone structure in constructing porous materials. Generally, the flexible building blocks are avoided to prevent the networks from collapsing in constructing high surface area porous materials. Our experimental results revealed that the introduction of the substituents can effectively decrease the probability of the network interpenetration from the longer struts and the intermolecular/intramolecular intercalation from the increased degree of conformation freedom in the flexible ether-linkage, the BET surface areas of PHCTFs increasing from 676 to 1270 m2 g-1. Meanwhile, the effects of introducing different sizes (methyl or phenyl group) and amounts (one or two) of substituents on the porosities of the target polymer networks were also investigated in detail. The high CO2 adsorption capacity of 10.3 wt % (273 K, 1 bar) can be ascribed to the strong affinity of the electron-rich N,O-containing networks with CO2. Excitingly, PHCTF-5 demonstrates the high CO2/N2 selectivity up to 138 (273 K, 1 bar), according to the ideal adsorbed solution theory (IAST) for the higher proportion of Vmicro accompanied the electron-rich heteroatoms characteristic. Such high CO2 adsorption capacity and good separation properties are superior to those of many other microporous organic polymers. These properties along with easily up-scalable synthesis make porous PHCTFs promising candidates applied in gas sorption and separation field.

Facile preparation of cross-linked polyimide aerogels with carboxylic functionalization for CO2 capture

In this study, highly cross-linked and completely imidized polyimide aerogels containing carboxyl groups were successfully synthesized using a mild sol-gel method at room temperature from 3,5-diaminobenzoic (DABA) and biphenyl-3,3′,4,4′-tetracarboxylic (BPDA) and cross-linked with 1,3,5-triaminophenoxybenzene. The densities of the obtained polyimide aerogels are between 0.116 and 0.386g/cm3, the specific surface areas range from 173 to 461m2/g, and the porosities are as high as 97%. The CO2 adsorption-desorption isotherms are reversible, and the CO2 uptakes at 25°C and 1bar are as high as 21.10cm3/g, which are comparable to those of previously reported microporous organic polymers. The high CO2 adsorptions are attributed to the abundance of electron-rich heteroatoms in the polyimide networks and to the presence of carboxyl groups, a type of CO2-philic group. The facile preparation and high CO2 adsorptive capacity indicate that polyimide aerogels may be ideal candidates for capturing CO2.