Nitrogen-rich porous adsorbents for CO2 capture and storage

Elucidating the non-covalent interactions in thiazole-carbon dioxide complexes through rotational spectroscopy and theoretical computations

The complexes formed between thiazole and carbon dioxide were studied to probe the non-covalent bonding properties between carbon dioxide and a heteroaromatic ring. The rotational spectra of the thiazole-CO2 complex were analyzed using a supersonic jet Fourier transform microwave spectrometer in conjunction with theoretical calculations. A rotational spectrum corresponding to the global minimum of the thiazole-CO2 complex was identified. The observed structure of the complex is stabilized by a C⋯N tetrel-bond, with additional stability provided by a C-H⋯O hydrogen bond. The computational analysis of the thiazole-(CO2)2 and thiazole-(CO2)3 complexes demonstrated the notable impact of C⋯N interactions on aggregation, with the significance of interactions between CO2 molecules increasing with the number of CO2 molecules present. NCI analysis, NBO analysis, and SAPT analysis were utilized to elucidate the properties of non-covalent interactions between thiazole and CO2, as well as those among CO2 molecules.

Sorption of Carbon Dioxide and Nitrogen on Porous Hyper-Cross-Linked Aromatic Polymers: Effect of Textural Properties, Composition, and Electrostatic Interactions

Porous hyper-cross-linked aromatic polymers are one of the emerging classes of porous organic polymers with the potential for industrial application. Four different porous polymeric materials have been prepared using different precursors (indole, pyrene, carbazole, and naphthalene), and the composition and textural properties were analyzed. The materials were characterized in detail using different physicochemical techniques like scanning electron microscopy, transmission electron microscopy, nitrogen adsorption at 77 K, Fourier transform infrared spectroscopy, X-ray diffraction, etc. The effect of textural properties and nitrogen species on carbon dioxide and nitrogen adsorption capacities and selectivity was studied and discussed. The carbon dioxide and nitrogen adsorption capacities were measured using a volumetric gas adsorption system. The adsorption data were fitted into different adsorption models, and the ideal absorbed solution theory was used to calculate adsorption selectivity. Among the studied samples, POP-4 shows the highest carbon dioxide and nitrogen adsorption capacities. While POP-1 shows maximum CO₂/N₂ selectivity of 78.0 at 298 K and 1 bar pressure. It is observed that ultra-micropores, which are present in the prepared materials but not measured during conventional surface area measurement via nitrogen adsorption at 77 K, play a very important role in carbon dioxide adsorption capacity and determining the carbon dioxide selectivity over nitrogen. Surface nitrogen also increases the CO₂ selectivity in the dual mode by increasing carbon dioxide adsorption via the acid-base interaction as well as by decreasing nitrogen adsorption due to N-N repulsion.

Superior Selective CO2 Adsorption and Separation over N2 and CH4 of Porous Carbon Nitride Nanosheets: Insights from GCMC and DFT Simulations

Development of high-performance materials for the capture and separation of CO₂ from the gas mixture is significant to alleviate carbon emission and mitigate the greenhouse effect. In this work, a novel structure of C₉N₇ slit was developed to explore its CO₂ adsorption capacity and selectivity using Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) calculations. Among varying slit widths, C₉N₇ with the slit width of 0.7 nm exhibited remarkable CO₂ uptake with superior CO₂/N₂ and CO₂/CH₄ selectivity. At 1 bar and 298 K, a maximum CO₂ adsorption capacity can be obtained as high as 7.06 mmol/g, and the selectivity of CO₂/N₂ and CO₂/CH₄ was 41.43 and 18.67, respectively. In the presence of H₂O, the CO₂ uptake of C₉N₇ slit decreased slightly as the water content increased, showing better water tolerance. Furthermore, the underlying mechanism of highly selective CO₂ adsorption and separation on the C₉N₇ surface was revealed. The closer the adsorption distance, the stronger the interaction energy between the gas molecule and the C₉N₇ surface. The strong interaction between the C₉N₇ nanosheet and the CO₂ molecule contributes to its impressive CO₂ uptake and selectivity performance, suggesting that the C₉N₇ slit could be a promising candidate for CO₂ capture and separation.

Non-solvent post-modifications with volatile reagents for remarkably porous ketone functionalized polymers of intrinsic microporosity

Chemical modifications of porous materials almost always result in loss of structural integrity, porosity, solubility, or stability. Previous attempts, so far, have not allowed any promising trend to unravel, perhaps because of the complexity of porous network frameworks. But the soluble porous polymers, the polymers of intrinsic microporosity, provide an excellent platform to develop a universal strategy for effective modification of functional groups for current demands in advanced applications. Here, we report complete transformation of PIM-1 nitriles into four previously inaccessible functional groups - ketones, alcohols, imines, and hydrazones - in a single step using volatile reagents and through a counter-intuitive non-solvent approach that enables surface area preservation. The modifications are simple, scalable, reproducible, and give record surface areas for modified PIM-1s despite at times having to pass up to two consecutive post-synthetic transformations. This unconventional dual-mode strategy offers valuable directions for chemical modification of porous materials.

Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO2 Capture

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO₂ adsorption capacity and also CO₂ /N₂ selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m²  g^-1 , total pore volume 0.3647 ccg^-1 ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m²  g^-1 , total pore volume 0.2978 ccg^-1 ). This fact leads to an enormous decrease in the CO₂ adsorption capacity and CO₂ /N₂ selectivity of TF-COF, though it shows stronger affinity towards CO₂ with a Qst of 37.76 KJ/mol. The more CO₂ adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO₂ /N₂ selectivity of 16.8, higher than that of TF-COF (CO₂ /N₂ selectivity 13.4).

Metal-Free Heptazine-Based Porous Polymeric Network as Highly Efficient Catalyst for CO2 Capture and Conversion

The capture and catalytic conversion of CO₂ into value-added chemicals is a promising and sustainable approach to tackle the global warming and energy crisis. The nitrogen-rich porous organic polymers are excellent materials for CO₂ capture and separation. Herein, we present a nitrogen-rich heptazine-based microporous polymer for the cycloaddition reaction of CO₂ with epoxides in the absence of metals and solvents. HMP-TAPA, being rich in the nitrogen site, showed a high CO₂ uptake of 106.7 mg/g with an IAST selectivity of 30.79 toward CO₂ over N₂. Furthermore, HMP-TAPA showed high chemical and water stability without loss of any structural integrity. Besides CO₂ sorption, the catalytic activity of HMP-TAPA was checked for the cycloaddition of CO₂ and terminal epoxides, resulting in cyclic carbonate with high conversion (98%). They showed remarkable recyclability up to 5 cycles without loss of activity. Overall, this study represents a rare demonstration of the rational design of POPs (HMP-TAPA) for multiple applications.

High capacity gas capture and selectivity properties of triazatruxene-based ultramicroporous hyper-crosslinked covalent polymer

Tuning the selective sorption features of microporous organic networks is of great importance for subsequent applications in gas uptake and hiding, while it is more attractive in terms of being both time and cost effective to realize these optimizations without using functional groups in the core and linker. “Knitting” is one of the easiest and most used method to obtain a broad scope of hyper-crosslinked polymers on a large scale from aromatic structures that do not contain functional groups for polymerization. By the use of Knitting method, a hypercrosslinked covalent ultramicroporous organic polymer was obtained via stepwise process from using triazatruxene (TAT) as core -a planar indole trimer- through anhydrous FeCl₃ catalyzed Friedel–Crafts alkylation using dimethoxybenzene as a linker. The resulting microporous polymer, namely TATHCCP was completely identified by analytical and spectral techniques after examined for gas properties (CO₂, CH₄, O₂, CO, and H₂) and selectivity (CO₂/N₂, CO₂/O₂, for CO₂/CO and CO₂/CH₄) up to 1 bar and increased temperatures (273 K, 296 K and 320 K). Although it has a relatively low (Brunauer–Emmett–Teller) BET specific surface area around 557 m²/g, it was seen to have a high CO₂ capture capacity approaching 10% wt. at 273 K. In accordance with (ideal adsorbed solution theory) IAST computations, it was revealed that interesting selectivity features hitting up to 60 for CO₂/N₂, 45 for CO₂/O₂, 35 for CO₂/CO, 13 for CO₂/CH₄ at lower temperatures revealed that the material has much better selectivity values than many HCP (hyper-crosslinked polymer) derivatives in the literature even from its most similar analog dimethoxymethane derivative TATHCP, which has a surface area of 950 m²/g.

Understanding the Effect of Water on CO2 Adsorption

Carbon capture from large sources and ambient air is one of the most promising strategies to curb the deleterious effect of greenhouse gases. Among different technologies, CO₂ adsorption has drawn widespread attention mostly because of its low energy requirements. Considering that water vapor is a ubiquitous component in air and almost all CO₂-rich industrial gas streams, understanding its impact on CO₂ adsorption is of critical importance. Owing to the large diversity of adsorbents, water plays many different roles from a severe inhibitor of CO₂ adsorption to an excellent promoter. Water may also increase the rate of CO₂ capture or have the opposite effect. In the presence of amine-containing adsorbents, water is even necessary for their long-term stability. The current contribution is a comprehensive review of the effects of water whether in the gas feed or as adsorbent moisture on CO₂ adsorption. For convenience, we discuss the effect of water vapor on CO₂ adsorption over four broadly defined groups of materials separately, namely (i) physical adsorbents, including carbons, zeolites and MOFs, (ii) amine-functionalized adsorbents, and (iii) reactive adsorbents, including metal carbonates and oxides. For each category, the effects of humidity level on CO₂ uptake, selectivity, and adsorption kinetics under different operational conditions are discussed. Whenever possible, findings from different sources are compared, paying particular attention to both similarities and inconsistencies. For completeness, the effect of water on membrane CO₂ separation is also discussed, albeit briefly.

Loading and Release of Charged and Neutral Fluorescent Dyes into and from Mesoporous Materials: A Key Role for Sensing Applications

The aim of this study is to determine the efficiency of loading and release of several zwitterionic, neutral, anionic and cationic dyes into/from mesoporous nanoparticles to find the optimum loading and release conditions for their application in detection protocols. The loading is carried out for MCM-41 type silica supports suspended in phosphate-buffered saline (PBS) buffer (pH 7.4) or in acetonitrile, involving the dyes (rhodamine B chloride, rhodamine 101 chloride, rhodamine 101 perchlorate, rhodamine 101 inner salt, meso-(4-hydroxyphenyl)-boron–dipyrromethene (BODIPY), sulforhodamine B sodium salt and fluorescein 27). As a general trend, rhodamine-based dyes are loaded with higher efficiency, when compared with BODIPY and fluorescein dyes. Between the rhodamine-based dyes, their charge and the solvent in which the loading process is carried out play important roles for the amount of cargo that can be loaded into the materials. The delivery experiments carried out in PBS buffer at pH 7.4 reveal for all the materials that anionic dyes are more efficiently released compared to their neutral or cationic counterparts. The overall best performance is achieved with the negatively charged sulforhodamine B dye in acetonitrile. This material also shows a high delivery degree in PBS buffer.

Triazine-based Organic Polymer-catalysed Conversion of Epoxide to Cyclic Carbonate under Ambient CO2 Pressure

In this work we have achieved epoxide to cyclic carbonate conversion using a metal-free polymeric catalyst under ambient CO₂ pressure (1.02 atm) using a balloon setup. The triazine containing polymer (CYA-ANIS) was prepared from cyanuric chloride (CYA-Cl) and o-dianisidine (ANIS) in anhydrous DMF as solvent by refluxing under the N₂ gas environment. The presence of triazine and amine functional groups in the polymer results in the adsorption of CO₂ up to 7 cc/g at 273 K. This inspired us to utilize the polymer for the conversion of a series of functionalised epoxides into their corresponding cyclic carbonates in the presence of tetrabutyl ammonium iodide (TBAI) as co-catalyst. The product has wide range of applications like solvent in lithium ion battery, precursor for polycarbonate, etc. The catalyst was efficient for the conversion of different mono and di-epoxides into their corresponding cyclic carbonates under atmospheric pressure in the presence of TBAI as co-catalyst. The study indicates that epoxide attached with electron withdrawing groups (like, CH₂ Cl, glycidyl ether, etc.) displayed better conversion compared to simple alkane chain attached epoxides. This is mainly due to the stabilization of electron rich intermediates produced during the reaction (e. g. epoxide ring opening or CO₂ incorporation into the halo-alkoxide anion). This catalyst mixture was capable to maintain its reactivity up to five cycles without losing its activity. Post catalytic characterization clearly supports the heterogeneous and recyclable nature of the catalyst.

Enhanced Adsorption of Carbon Dioxide from Simulated Biogas on PEI/MEA-Functionalized Silica

A series of efficient adsorbents were prepared by a wet-impregnation method for CO₂ separation from simulated biogas. A type of commercially available silica, named as FNG-II silica (FS), was selected as supports. FS was modified with a mixture of polyethyleneimine (PEI) and ethanolamine (MEA) to improve the initial CO₂ adsorption capacity and thermal stability of the adsorbents. The influence of different adsorbents on CO₂ adsorption performance was investigated by breakthrough experiments. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and N₂ adsorption–desorption isotherm were used to characterize the silica before and after impregnating amine. Additionally, the thermal stability of adsorbents was measured by differential thermal analysis (TDA). Silica impregnated with mixtures of MEA and PEI showed increased CO₂ adsorption performance and high thermal stability compared with those obtained from silica impregnated solely with MEA or PEI. With a simulated biogas flow rate of 100 mL/min at 0.2 MPa and 25 °C, FS-10%MEA-10%PEI exhibited a CO₂ adsorption capacity of ca. 64.68 mg/g which increased by 81 % in comparison to FS-20%PEI. The thermal stability of FS-10%MEA-10%PEI was evidently higher than that of FS-20%MEA, and a further improvement of thermal stability was achieved with the increasing value of PEI/MEA weight ratio. It was showed that MEA was able to impose a synergistic effect on the dispersion of PEI in the support, reduce the CO₂ diffusion resistance and thus increase CO₂ adsorption performance. Additionally, if the total percentage of amine was the same, FS impregnated by different ratios of PEI to MEA did not exhibit an obvious difference in CO₂ adsorption performance. FS-15%PEI-5%MEA could be regenerated under mild conditions without obvious loss of CO₂ adsorption activity.

Structure and C⋯N tetrel-bonding of the isopropylamine–CO2 complex studied by microwave spectroscopy and theoretical calculations

The structural and energetic features of C⋯N tetrel bond and C–H⋯O hydrogen bonds linking CO₂ and aliphatic amines were characterized with rotational spectroscopy and quantum chemical calculations.

Marine and Freshwater Feedstocks as a Precursor for Nitrogen-Containing Carbons: A Review

Marine-derived as well as freshwater feedstock offers important benefits, such as abundance, morphological and structural variety, and the presence of multiple elements, including nitrogen and carbon. Therefore, these renewal resources may be useful for obtaining N- and C-containing materials that can be manufactured by various methods, such as pyrolysis and hydrothermal processes supported by means of chemical and physical activators. However, every synthesis concept relies on an efficient transfer of nitrogen and carbon from marine/freshwater feedstock to the final product. This paper reviews the advantages of marine feedstock over synthetic and natural but non-marine resources as precursors for the manufacturing of N-doped activated carbons. The manufacturing procedure influences some crucial properties of nitrogen-doped carbon materials, such as pore structure and the chemical composition of the surface. An extensive review is given on the relationship between carbon materials manufacturing from marine feedstock and the elemental content of nitrogen, together with a description of the chemical bonding of nitrogen atoms at the surface. N-doped carbons may serve as effective adsorbents for the removal of pollutants from the gas or liquid phase. Non-recognized areas of adsorption-based applications for nitrogen-doped carbons are presented, too. The paper proves that nitrogen-doped carbon materials belong to most of the prospective electrode materials for electrochemical energy conversion and storage technologies such as fuel cells, air⁻metal batteries, and supercapacitors, as well as for bioimaging. The reviewed material belongs to the widely understood field of marine biotechnology in relation to marine natural products.

Highly selective adsorption of CO over CO2 in a Cu(I)-chelated porous organic polymer

Cu(I) species were successfully chelated to nitrogen atoms in a nitrogen-rich porous organic polymer (SNW-1) by mixing with a CuCl solution (Scheme 1). Although pristine SNW-1 adsorbs CO₂ better than CO, Cu(I)-incorporated SNW-1 (nCu(I)@SNW-1) shows selective CO adsorption over CO₂ because of the π-complexation of CO with Cu(I). To the best of our knowledge, this is the first CO/CO₂ selectivity observed for POP-based materials. 1.3Cu(I)@SNW-1 exhibits high CO/CO₂ selectivity (23) at 1bar and a large CO working capacity (0.6mmol/g) at 0.1-1bar. Moreover, the breakthrough and thermogravimetric experiments show that 1.3Cu(I)@SNW-1 can effectively separate CO from CO₂ under dynamic mixture conditions and can be easily regenerated under mild regeneration conditions without heating the column. Furthermore, 1.3Cu(I)@SNW-1 exhibited a good stability under exposure to atmospheric air for 3h or 9h. These results suggest that chelating Cu(I) species to a nitrogen-rich porous organic polymer can be an efficient strategy to separate and recover CO from CO/CO₂ mixtures.

Long-Term Effect of Steam Exposure on CO2 Capture Performance of Amine-Grafted Silica

This study investigates the hydrothermal stability of triamine-grafted CO₂ adsorbent based on a commercial-grade silica (CARiACT, P10). Grafting was conducted in dry and wet conditions at 85 °C. At optimum grafting conditions using 0.2 cm³ water and 1.5 cm³ aminosilane per gram of silica, the highest CO₂ uptake of 1.93 mmol/g at 50 °C was obtained. This material was exposed to steam at 120 °C for up to 360 h. It was observed that increasing the duration of steam exposure from 3 to 24 h reduced adsorption uptake at 25 °C by 56%. However, the CO₂ uptake reduction was much less severe at higher adsorption temperatures, reaching 21% at 50 °C and only 4% at 75 °C. Conducting steam treatment for 360 h reduced adsorption uptake at 25, 50, and 75 °C by 83, 61, and 26%, respectively. For this extreme steaming experiment, the decrease in CO₂ uptake at all adsorption temperatures was attributed to the reduction of the sorbent average pore width, increasing diffusional mass transfer resistance. The results revealed that steam exposure did not reduce the amine loading or deactivate the amine groups; however, increasing exposure time decreased the average pore width, until partial collapse of material structure. Nevertheless, the large average pore width (21 nm) of the P10 silica led to higher hydrothermal stability of the amine-grafted sorbent compared to those with ordered pore structure supports, such as SBA-15 silica.

Cage amines in the metal–organic frameworks chemistry

Nitrogen-rich porous materials have outstanding gas sorption and separation capacity. Using cage amines in the synthesis of metal–organic frameworks is a simple approach for generating the free nitrogen donor centers within the channels of porous materials without the post-synthetic modification. 1,4-Diazabicyclo[2.2.2]octane has a linear arrangement of nitrogen centers and can be used as a linear linker for the design of porous MOF materials. Urotropine has four nitrogen atoms and can act as a tetrahedral four-connected, pyramidal three-connected or bent two-connected linker. Such a diversity of coordination possibilities enriches the structural chemistry of MOFs and allows obtaining the frameworks with unique secondary building units and topology. The presence of cage amines in the structure affects the sorption characteristics of the materials. They demonstrate high selectivity to CO2 and can participate as a heterogeneous base catalyst in the organic reactions. Besides that the cage-amine based metal–organic frameworks demonstrate photoluminescent properties and can be used as nanoreactors for photochemical transformations. These compounds are also an important object of thermodynamic studies helping us better understand the nature of host–guest interaction in the supramolecular systems.

Trends and challenges for microporous polymers

Recent trends and challenges for the emerging materials class of microporous polymers are reviewed. See the main article for graphical abstract image credits.

Two metal–organic frameworks sharing the same basic framework show distinct interpenetration degrees and different performances in CO2 catalytic conversion

Two metal–organic frameworks having the same basic framework but different interpenetration degrees show different catalytic activities in CO₂ cycloaddition reactions.

A highly porous metal–organic framework for large organic molecule capture and chromatographic separation

A highly porous metal–organic framework with large pores presents large molecule based applications probed by organic dye molecules.

Highly porous photoluminescent diazaborole-linked polymers: synthesis, characterization, and application to selective gas adsorption

Highly porous and photoluminescent diazaborole-linked polymers are targeted by boron–nitrogen bond formation through simple condensation reactions. The resultant polymers exhibit remarkable gas uptake and tunable photoluminescent properties.

Imine-Linked Polymer Based Nitrogen-Doped Porous Activated Carbon for Efficient and Selective CO2 Capture

The preparation of nitrogen-doped activated carbon (NACs) has received significant attention because of their applications in CO2 capture and sequestration (CCS) owing to abundant nitrogen atoms on their surface and controllable pore structures by carefully controlled carbonization. We report high-surface-area porous N-doped activated carbons (NAC) by using soft-template-assisted self-assembly followed by thermal decomposition and KOH activation. The activation process was carried out under different temperature conditions (600-800 °C) using polyimine as precursor. The NAC-800 was found to have a high specific surface area (1900 m2 g-1), a desirable micropore size below 1 nm and, more importantly, a large micropore volume (0.98 cm3 g-1). NAC-800 also exhibits a significant capacity of CO2 capture i.e., over 6. 25 and 4.87 mmol g-1 at 273 K and 298 K respectively at 1.13 bar, which is one of among the highest values reported for porous carbons so far. Moreover, NAC also shows an excellent separation selectivity for CO2 over N2.

Solid Amine Adsorbent Prepared by Molecular Imprinting and Its Carbon Dioxide Adsorption Properties

A carbon dioxide imprinted solid amine adsorbent (IPEIA-R) with polyethylenimine (PEI) as a skeleton was conveniently prepared by using glutaraldehyde to cross-link carbon dioxide-preadsorbed PEI. As confirmed by FTIR, FT-Raman, and ¹³ C NMR spectroscopy, CO₂ preadsorbed on PEI could occupy the reactive sites of amino groups and act as a template for imprinting in the cross-linking process. The imino groups formed from the cross-linking reaction between glutaraldehyde and PEI could be reduced by NaBH₄ to form CO₂ -adsorbable amino groups. The adsorption results indicated that CO₂ imprinting and reduction of imino groups by NaBH₄ endowed the adsorbent with a higher CO₂ adsorption capacity. Compared with PEI-supported mesoporous adsorbents, the solid amine adsorbent with PEI as a skeleton can avoid serious pore blockage and CO₂ diffusion resistance, even with a high amine content. The solid amine adsorbent with PEI as a skeleton showed a remarkable CO₂ adsorption capacity (8.56 mmol g^-1 ) in the presence of water at 25 °C, owing to the high amine content and good swelling properties. It also showed promising regeneration performance and could maintain almost the same CO₂ adsorption capacity after 15 adsorption-desorption cycles.

Bimetallic Metal-Organic Frameworks: Probing the Lewis Acid Site for CO2 Conversion

A highly porous metal-organic framework (MOF) incorporating two kinds of second building units (SBUs), i.e., dimeric paddlewheel (Zn2 (COO)4 ) and tetrameric (Zn4 (O)(CO2 )6 ), is successfully assembled by the reaction of a tricarboxylate ligand with Zn(II) ion. Subsequently, single-crystal-to-single-crystal metal cation exchange using the constructed MOF is investigated, and the results show that Cu(II) and Co(II) ions can selectively be introduced into the MOF without compromising the crystallinity of the pristine framework. This metal cation-exchangeable MOF provides a useful platform for studying the metal effect on both gas adsorption and catalytic activity of the resulted MOFs. While the gas adsorption experiments reveal that Cu(II) and Co(II) exchanged samples exhibit comparable CO2 adsorption capability to the pristine Zn(II) -based MOF under the same conditions, catalytic investigations for the cycloaddition reaction of CO2 with epoxides into related carbonates demonstrate that Zn(II) -based MOF affords the highest catalytic activity as compared with Cu(II) and Co(II) exchanged ones. Molecular dynamic simulations are carried out to further confirm the catalytic performance of these constructed MOFs on chemical fixation of CO2 to carbonates. This research sheds light on how metal exchange can influence intrinsic properties of MOFs.

The role of the internal molecular free volume in defining organic porous copolymer properties: tunable porosity and highly selective CO2 adsorption

This paper presents novel azo-connected copolymerized networks derived from triptycene and spirobifluorene for high carbon dioxide selective capture.

Channel-wall functionalization in covalent organic frameworks for the enhancement of CO2 uptake and CO2/N2 selectivity

Two structurally similar groups with one being CO₂-philic but the other not were anchored into the channel walls of 2D COFs. The decreased surface area of COFs undoubtedly decreased CO₂ adsorption if too many functional groups were introduced.

Expanded Porphyrins as Two-Dimensional Porous Membranes for CO2 Separation

Porphyrin-based two-dimensional polymers have uniform micropores and close to atom-thin thicknesses, but they have not been explored for gas separation. Herein we design various expanded porphyrin derivatives for their potential application in membrane gas separation, using CO2/N2 as an example. Pore sizes are determined based on both van der Waals radii and electron density distribution. Potential energy curves for CO2 and N2 passing through are mapped by dispersion-corrected density functional theory calculations. The passing-through barriers are used to evaluate CO2/N2 separation selectivity. Promising subunits for CO2 separation have been selected from the selectivity estimates. 2D membranes composed of amethyrin derivatives are shown to have high ideal selectivity on the order of 10(6) for CO2/N2 separation. Classical molecular dynamics simulation yields a permeance of 10(4)-10(5) GPU for CO2 through extended 2D membranes based on amethyrin derivatives. This work demonstrates that porphyrin systems could offer an attractive bottom-up approach for 2D porous membranes.

Amine-based CO2 capture technology development from the beginning of 2013-a review

It is generally accepted by the scientific community that anthropogenic CO2 emissions are leading to global climate change, notably an increase in global temperatures commonly referred to as global warming. The primary source of anthropogenic CO2 emissions is the combustion of fossil fuels for energy. As society's demand for energy increases and more CO2 is produced, it becomes imperative to decrease the amount emitted to the atmosphere. One promising approach to do this is to capture CO2 at the effluent of the combustion site, namely, power plants, in a process called postcombustion CO2 capture. Technologies to achieve this are heavily researched due in large part to the intuitive nature of removing CO2 from the stack gas and the ease in retrofitting existing CO2 sources with these technologies. As such, several reviews have been written on postcombustion CO2 capture. However, it is a fast-developing field, and the most recent review papers already do not include the state-of-the-art research. Notable among CO2 capture technologies are amine-based technologies. Amines are well-known for their reversible reactions with CO2, which make them ideal for the separation of CO2 from many CO2-containing gases, including flue gas. For this reason, this review will cover amine-based technology developed and published in and after the year 2013.