Selective CO2 Capture Research Articles

Selective CO2 adsorption at low pressure with a Zr-based UiO-67 metal–organic framework functionalized with aminosilanes

MOF UiO-67, although without open metal site, was loaded with aminosilanes for selective CO2 capture. One modified UiO-67 showed a remarkable performance in CO2 adsorption like huge selectivity of 407 which is 163 times that of pristine UiO-67.

Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications.

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO2 capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh3)4. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (Td10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m2 g–1), high CO2 adsorption (5.40 mmol g–1 at 273 K), excellent capacitance (735 F g–1), and a capacitance retention of up to 95% after 2000 galvanostatic charge–discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C.

Nanocast nitrogen-containing ordered mesoporous carbons from glucosamine for selective CO2 capture

D-glucosamine is investigated as a non-toxic and sustainable carbon/nitrogen (C/N) source for the templated synthesis of nitrogen-containing CMK-8 ordered mesoporous carbons (NOMCs) conceived for selective CO2 uptake. Pyrolysis temperature is varied during nanocasting using the KIT-6 silica hard template to tailor microporosity and nitrogen inclusions. NOMCs exhibit large surface area (600–1000 m2 g-1) and excellent pore ordering. The CO2/adsorbent interaction energy is estimated by the isosteric enthalpy of adsorption (∼33–40 kJ mol-1) and Henry's constants. The role of nitrogen content (∼7–12 at.%) and of each type of N-species on CO2 adsorption is studied by X-ray photoelectron spectroscopy, and CO2/N2 selectivity is attributed, being pyridinic functionalities the most effective ones. NOMCs are tested at different temperatures, gas flow compositions, reversibility, and so on; in all tested conditions, they outperform a homologous bare sucrose-derived carbon. Enhancing micropore volume allows achieving maximum adsorption capacity in pure CO2 (1.47 mmol g−1 at 30 °C/0.9 bar), whereas increasing surface N-content accounts for the highest selectivity in CO2/N2 mixtures (20/80 v/v) at 35 °C/1 bar (maximum CO2 uptake 0.82 mmol g−1). The combination of a suitable C/N precursor and the hard templating synthetic route is effective for obtaining high-performing, sustainable, and reusable selective CO2 sorbents, without any activation steps or N-doping post-treatments.

Reduced graphene oxide -MnO2 nanocomposite for CO2 capture from flue gases at elevated temperatures

The newly prepared reduced graphene oxide-MnO2 (rGO-MnO2) nanocomposite has exhibited highly selective CO2 adsorption from gaseous mixtures at elevated temperatures. The Mn2+ basic sites are scattered over the rGO-MnO2 nanocomposite which produce an effective BET surface area of 710 m2 g−1 for selective CO2 capture. The selective adsorption of CO2 (5.87 mmol g−1) over N2 (0.36 mmol g−1) and CH4 (0.41 mmol g−1) at 298 K/1 bar was achieved by the nanocomposite. The heat of adsorption followed a unique correlation with the quantity of CO2 adsorbed and fits well to the Fowler-Guggenheim equation. The mechanism of CO2 adsorption on the nanocomposite was complemented with molecular modelling and simulations. The rGO-MnO2 have shown better CO2 adsorption capacity of 28.5 mmol g−1 at 323 K/20 bar as compared to zeolite derivatives, MOFs, and carbons as reported in the literature. The formation of inert frameworks with 3–6 nm porous structure in the nanocomposite thermally stabilizes to capture CO2 repeatedly. The nanocomposite with adsorption capacity of 3.69 mmol g−1 at 373 K/1 bar is quite close to real-life conditions for flue gas treatment.

Selective CO2 capture and multiresponsive luminescent sensor in aqueous solutions of cadmium metal-organic framework based on trigonal rigid ligand

We report here a new fashioned cd-metal-organic framework (MOF) exhibiting a (5, 6)-connected 2-nodal net, [Cd3(LMe)(H2O)]·DMF·3H2O constituted by two different metal clusters and a trigonal rigid 6-connected ligand. The analytic reveal that complex is a 3D structure. Each (LMe)6− ligand is linked to five dinuclear SBUs, which forms a 2D lay, and Cd1 ions are linked by two different deprotonated carboxylates to construct a 3D porous framework. IAST manifested that the selectivity coefficients under 1 bar for the N2/CO2 (85: 15) and CH4/CO2 (50: 50) compounds were 86 and 6 at 273 K, respectively. Complex exhibited selectivity of CO2 relative to N2 and CH4 upon removal of solvates. Moreover, the complex caused emission quenching in the existence of Fe3+, MnO4− and CHCl3 organic solvent molecules. The multi-response fluorescence probe has lofty sensitivity and low limit of detection in the existence of Fe3+ and MnO4−. It thus appears that the Cd-MOF is not only a useful strategy for CO2 capture, but a fluorescent transducer for simultaneous exploration of organic solvent, metal ions and inorganic anions.

Construction of two new Co(II)-organic frameworks based on diverse metal clusters: Highly selective C2H2 and CO2 capture and magnetic properties

Two new Co(II)-complexes, namely, [(NH2Me2)2][Co4(L)2(μ2-O)2(H2O)5DMF]·2DMF·3H2O (1), [(NH2Me2)5][Co12(L)6(μ3-O)4(HCOO)(H2O)6]·2DMF·8H2O (2) were solvothermally constructed based on a rigid pyridine polycarboxylate ligand (H4L, 2,6-di(2′,5′-dicarboxyphenyl) pyridine). Complex 1 and 2 dislay 3D frameworks with various metal cluster. Complex 1 is a 3D porous framework with a (4,8)-connected topology featured by 1D pore structure in a-axis direction with binuclear cluster [Co2(COO)4O] and tetranuclear cluster [Co4(COO)8O2]. Complex 2 possess trinuclear cluster [Co3(COO)6O] and binuclear cluster [Co2(COO)5O], and it can be clearly observed that 2 is assembled by numbers of nano-cages by twisting a certain angle. Notably, the gas sorption behaviour investigation indicates that the desolvated 1a displays uptake capacity and adsorption selectivity to C2H2 and CO2 over CH4. Furthermore, the results of magnetic studies show that complex 2 exhibits antiferromagnetic interactions between Co2+ ions.

Synthesis, characterization, and selective CO2 capture performance of a new type of activated carbon-geopolymer composite adsorbent

Surface modification of activated carbon is an effective strategy to enhance its adsorption performance. However, most studies have focused on the use of chemical modifiers, and the products are usually in a powder form. Herein, we report the effective surface modification of activated carbon through geopolymer chemistry via simultaneous alkali-activated functionalization and polycondensation, thus yielding a monolithic adsorbent. The CO2 adsorption capacity of the optimized adsorbent was 2.25 times higher than that of the average of the constituents. Moreover, geopolymers can also function as efficient binders to supply a sufficient compressive strength of 22.3 MPa for the resultant adsorbent. Under different conditions, significant surface texture reconstruction of activated carbon was observed and confirmed via systematic XRD, FESEM, BET, XPS, and Raman spectrum characterisations combined with density functional theory (DFT) calculations. The effective surface modification was associated with the high alkaline environment during the geopolymerization reaction, which intercalates –CO, -OK, and -COOK functional groups on the activated carbon surface. These groups exhibited stronger CO2 affinity than that of pure activated carbon and thus endowed the high-strength adsorbent with enhanced CO2 adsorption capacity.

Highly selective CO2 capture and photoreduction over porous carbon nitride foams/LDH monolith

Sunlight-driven photocatalytic CO2 into useful carbon compounds is an ideal way to mitigate the greenhouse effect. However, this strategy is limited by poor light absorption and rapid photoexcited electron-hole recombination of traditional photocatalysts. Here, a g-C3N4 (CN) foam/LDH heterojunction monolith (NCF) was fabricated by growing NiFe-LDH in situ on the porous CN foam substrate. The composite had good air permeability and light transmittance, which improves light-harvesting, CO2 capture, and interfaces charge transfer of the NCF. The results show that the NCF catalyst has good CO2 adsorption performance (1.52 mmol g−1) and enhanced CO2 photoreduction activity (55.1 μmol g-1h−1), which is ∼ 10 times higher than that of pure LDHs powder. Furthermore, the practical applicability of the NCF monolith with different thicknesses is illustrated via the CO2 photoreduction test for the first time. This work could shed light on the development of dual-functional materials for efficient capture and photoreduction of CO2.

Transformation of waste cornstalk into versatile porous carbon adsorbent for selective CO2 capture and efficient methanol adsorption

For the purpose of selective CO2 capture and efficient methanol adsorption, versatile porous carbon adsorbents are prepared from waste cornstalk by using hydrothermal carbonization treatment and the subsequent KOH activation process. The resultant adsorbents are characterized with different techniques, and the effects of activation degree on the porous structure and chemical components are discussed. The influence of porous texture and heteroatoms doping on the performance of CO2 capture and methanol adsorption has been systematically analyzed. For CO2 capture, the ultra-micropore is the dominant factor under 1 bar, while the heteroatoms N and O have important cooperation effect under 0.15 bar. The methanol adsorption uptakes under 95 mbar and 10 mbar are closely associated with the specific surface area and ultra-micropore volume, respectively. The adsorbents exhibit remarkable CO2 adsorption uptake of 3.97 mmol g−1 at 1 bar, and desirable methanol adsorption uptake of 18.88 mmol g−1 at 95 mbar, in the temperature of 25 °C. The adsorbents also feature excellent reusability and good selectivity for CO2 over N2, as well as methanol over water. This work provides a feasible approach to prepare low-cost porous carbon adsorbents, which may inspire new research interests and provide necessary theoretical guidance for the application and investigation of biomass-derived carbonaceous adsorbents for CO2 capture and methanol adsorption.

Hierarchical porous carbon beads for selective CO2 capture

Excessive CO2 emissions from increased energy consumption are causing an environmental disaster that threatens humanity. Herein, we report the development of hierarchical porous carbon beads with interconnected micro- and mesopores for selective CO2 capture. Hierarchical porous carbon beads were prepared by the carbonization of potassium-exchanged phenol formaldehyde resin (PFR) beads obtained from exchange of K+ to the PFR OH groups. Interestingly, the carbonized K2CO3-treated PFR (CPFRs) exhibited notably high surface areas and total pore volumes with interconnected micro- and mesopores. Based on their high porosities and nitrogen contents, the K2CO3-treated CPFR beads adsorbed 7.80 wt% CO2 at 0.15 bar and 298 K, which is an adsorption result that is much higher than those (4.41 wt% and 5.33 wt%) of pristine and KOH-treated CPFR beads, respectively. More importantly, the ideal CO2/N2 selectivity (52.6) of K2CO3-treated CPFR beads, as determined by Henry’s constant at room temperature, is superior to those (24.2 and 28.6) of pristine and KOH-treated CPFR beads, respectively. Breakthrough experiments with 15 % CO2 in N2, which has a similar partial pressure to the CO2 partial pressure in flue gases from coal power plants, revealed that K2CO3-treated CPFR beads selectively adsorb 5.5 wt% of CO2 over N2. This selective CO2 capacity is superior to those reported in other porous carbon materials. Therefore, to reduce CO2 emissions, hierarchical porous carbon beads with interconnected micro- and mesopores can play an important role in CO2 capture and separation.

The potential of additively manufactured membranes for selective separation and capture of CO2

The potential of additively manufactured membranes for selective separation and capture of CO2

Assembly of amine-functionalized graphene oxide for efficient and selective adsorption of CO2

Amine-functionalized solid adsorbents show promising potential for the capture of CO2, a harmful greenhouse gas which is regarded as the major cause of global warming. In this study, three amine functionalities of triethylenetetramine (TETA), pentaethylenehexamine (PEHA), and meta-phenylenediamine (MPD) were separately anchored to the GO surface. The analyzing methods, including Fourier transform infrared spectroscopy (FTIR), CHNS elemental analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2 adsorption-desorption were used to study the characteristics of the synthesized GO series. The equilibrium adsorption of CO2 on GO and amine-functionalized GO (GO-NH2) were experimentally measured at 298, 308, and 318 K and pressure range of 0–14 bar. The CO2 uptake was strikingly improved from 0.39 mmol/g for GO to 0.61, 0.74, and 0.91 mmol/g for GO-PEHA, GO-TETA, and GO-MPD adsorbents at 298 K and 1 bar, respectively. The prediction of the selectivity of the adsorbents based on the ideal adsorbed solution theory (IAST) exhibited the excellent selectivity of the adsorbents, in particular for GO/MPD around 21.21 for the selective capture of CO2 over N2 under ambient conditions. The isosteric heats of adsorption indicated the physisorption of CO2 on amine-modified GO samples and also its precursor. The high CO2/N2 selectivity obtained in this study and cyclic operation tests prove that GO-NH2 samples can be applied as an impressive adsorbent to capture CO2 from flue gas.

High yield nitrogen-doped carbon monolith with rich ultramicropores prepared by in-situ activation for high performance of selective CO2 capture

Constrained by the unsatisfactory physical adsorption capacity and the low carbon yield from chemical activation, practical utilization of carbon materials for CO2 capture and separation (CCS) remains a huge challenge. Herein, we proposed a novel in-situ activation methodology to prepare a category of porous carbon monoliths in which the potassium ion activation sites are evenly introduced through acid-base reaction, contributing to the high carbon yield, abundant ultramicropores as well as rich nitrogen content. Tested at adsorption temperatures of 0, 25 and 40 °C, the as-prepared carbon monoliths display remarkable static CO2 uptake (7.1, 5.0 and 3.7 mmol/g, respectively) and excellent selective adsorption ability in dynamic breakthrough experiment with a binary mixture of CO2/N2 (68, 63 and 67, respectively). Along with the experiments, the CO2 adsorption mechanism was determined by calculating the adsorption density and adsorption energy on slit pore with various pore sizes and surface functionalities using grand canonical Monte Carlo (GCMC) simulation. The narrow micropores can significantly and effectively increase the CO2adsorption capacity, while the functional groups played the second role.

Environmentally benign melamine functionalized silica-coated iron oxide for selective CO2 capture and fixation into cyclic carbonate

The development of new materials capable of fixing CO2 into value-added products has become an exciting research field. Besides mitigating the rising level of CO2, such materials also enable CO2 as a C1 carbon source for useful industrial synthons. This article reports on the stepwise synthesis of a melamine functionalized silica-coated iron oxide (FSNM) material for selective CO2 capture and its catalytic conversion into a useful product. The synthesis of FSNM has been achieved by covalently grafting the melamine group in the pores of mesoporous silica-coated Fe3O4 (Fe3O4@SiO2) particle using isocyanate as a cross-linker. While the Fe3O4 core, owing to its superparamagnetic property, enables the easy retrieval of the material from the reaction mixture and, thus, enhances the recyclability, mesoporous silica coating offers a larger surface area for adsorption. The organic functionalities, containing melamine and carbamide moieties, facilitate the selective adsorption of CO2 on the material with a maximum CO2 uptake of 0.48 mmol/g at 1 bar and 298 K with excellent CO2/N2 selectivity. Moreover, the acid-base interactions between the acidic CO2 and basic amine groups enable the FSNM to catalyze the cycloaddition of CO2 with different epoxides to afford a series of cyclic carbonates, in the presence of tetrabutylammonium bromide (TBAB) as a co-catalyst, under facile and solvent-free conditions. These results strongly support that melamine functionalized Fe3O4@SiO2 affords new aspects towards environmentally friendly and recoverable hybrid adsorbent for adsorption and fixation of CO2 into the valuable products.

Thermal and Gas Adsorption Properties of Tröger's Base/Diaza‐cyclooctane Hybrid Ladder Polymers

AbstractA polymer of intrinsic microporosity (PIM) consisting of Tröger's base (TB) undergoes ring opening of the bicyclic amine upon N‐methylation followed by alkaline hydrolysis, resulting in a hybrid ladder polymer that contains diazacyclooctane (DACO) units with tert‐ and sec‐amino groups. The hybrid ladder polymers with various TB/DACO ratios can be prepared depending on the reaction conditions. Here we report a systematic study on the effect of DACO content on the thermal and gas adsorption properties of the hybrid ladder polymer. Using a PIM derived from 2,5‐diamino‐p‐xylene, we prepared hybrid ladder polymers with a DACO content ranging from 19% to 55% while having a similar molecular weight. The thermal stability of the hybrid ladder polymers, evaluated by thermogravimetric analysis, is decreased with the increase in DACO content. Based on gas adsorption measurements, the increase in DACO content results in the decrease in the BET surface area but improves the gas adsorption selectivity for CO2 against N2, likely due to high basicity of the sec‐amino group of DACO unit. This result demonstrates that the partial TB‐to‐DACO conversion of the TB‐based PIM may provide a simple but useful strategy to design polymer materials that enable selective CO2 capture and/or separation.

Amine or Azo functionalized hypercrosslinked polymers for highly efficient CO2 capture and selective CO2 capture

Hypercrosslinked polymers (HCPs) are very promising for large-scale applications due to their easy preparation, high thermal stability, and good capability of CO2 capture. Currently, many amine-functionalized porous materials are prepared through two steps. In this paper, the amine-functionalized HCPs was obtained with a one-step method and it showed a high CO2 adsorption up to 4.24 mmol/g at 273.15 K. In addition, since the azo-functionalized porous materials have many potential applications like the photoresponsive ‘smart’ materials, azobenzene is an attracting functional group for the development of porous materials. Herein, the azo-functionalized HCPs is firstly reported, and it is used as CO2 adsorbents (3.02 mmol/g at 273.15 K) performing good CO2/N2 selectivity (34.52 at 298.15 K).

Macrocyclic Arenes-Based Conjugated Macrocycle Polymers for Highly Selective CO2 Capture and Iodine Adsorption.

Incorporating synthetic macrocycles with unique structures and distinct conformations into conjugated macrocycle polymers (CMPs) can endow the resulting materials with great potentials in gas uptake and pollutant adsorption. Here, four CMPs (CMP-n, n=1-4) capable of reversibly capturing iodine and efficiently separating carbon dioxide are constructed from per-triflate functionalized leaning tower[6]arene (LT6-OTf) and [2]biphenyl-extended pillar[6]arene (BpP6-OTf) via Pd-catalyzed Sonogashira-Hagihara cross-coupling reaction. Intriguingly, owing to the appropriate cavity size of LT6-OTf and the numerous aromatic rings in the framework, the newly designed CMP-4 possesses an outstanding I2 affinity with a large uptake capacity of 208 wt % in vapor and a great removal efficiency of 94 % in aqueous solutions. To our surprise, with no capacity to accommodate nitrogen, CMP-2 constructed from BpP6-OTf is able to specifically capture carbon dioxide at ambient conditions.

Fluorocarbon-Functionalized Superhydrophobic Metal-Organic Framework: Enhanced CO2 Uptake via Photoinduced Postsynthetic Modification.

The design and synthesis of porous materials for selective capture of CO2 in the presence of water vapor is of paramount importance in the context of practical separation of CO2 from the flue gas stream. Here, we report the synthesis and structural characterization of a photoresponsive fluorinated MOF {[Cd(bpee)(hfbba)]·EtOH}n (1) constructed by using 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (hfbba), Cd(NO3)2, and 1,2-bis(4-pyridyl)ethylene (bpee) as building units. Due to the presence of the fluoroalkyl -CF3 functionality, compound 1 exhibits superhydrophobicity, which is validated by both water vapor adsorption and contact angle measurements (152°). The parallel arrangement of the bpee linkers makes compound 1 a photoresponsive material that transforms to {[Cd2(rctt-tpcb)(hfbba)2]·2EtOH}n (rctt-tpcb = regio cis,trans,trans-tetrakis(4-pyridyl)cyclobutane; 1IR) after a [2 + 2] cycloaddition reaction. The photomodified framework 1IR exhibits increased uptake of CO2 in comparison to 1 under ambient conditions due to alteration of the pore surface that leads to additional weak electron donor-acceptor interactions with the -CF3 groups, as examined through periodic density functional theory calculations. The enhanced uptake is also aided by an expansion of the pore window, which contributes to increasing the rotational entropy of CO2, as demonstrated through force field based free energy calculations.

Efficient synthetic approach for nanoporous adsorbents capable of pre- and post-combustion CO2 capture and selective gas separation

The level of CO2 in the atmosphere has increased rapidly due to vast quantities of fossil fuel combustion emissions, and it is accelerating global warming. Hence, pre- and post-combustion CO2 capture and storage (CCS) has become a vital necessity. Cost-effective and efficient nanoporous adsorbents for pre- and post-combustion CO2 capture were developed in this study. The highly porous and oxygen-rich carbon adsorbents were prepared in a facile one-pot process via the direct chemical activation of a molecularly imprinted polymer (MIP) and a MIP composite with activated carbon. The porous carbon adsorbent prepared from the MIP composite had a large specific surface area and specific pore volume of 3010 m2 g−1 and 1.506 cm3 g−1, respectively. Its bimodal pore structure contained micropores and mesopores. This nanoporous carbon adsorbent was rich in electron-dense oxygen presented in a variety of oxygen surface functional groups, which was also advantageous for CCS. These merits afforded selective CO2 adsorption and a high storage capacity under pre- and post-combustion conditions. The efficient carbon adsorbent can be stored 22.1 mmol g−1 and 3 mmol g−1 of CO2 at 25 bar and 1 bar, respectably, which was in the upper range of values reported for porous carbon. Selective CO2 capture by the carbon adsorbents was confirmed by evaluating their selectivity in CO2/CH4, CO2/N2, and CO2/H2 binary gas mixtures at 298 K based on the ideal adsorbed solution theory (IAST). The most effective adsorbent had CO2/H2 (40:60) and CO2/N2 (50:50) selectivity of 534 and 22.6, respectively. The isosteric heat of CO2 adsorption on the porous carbon adsorbents further corroborated the selective CO2 capture.

Dual-functionalization actuated trimodal attribute in an ultra-robust MOF: exceptionally selective capture and effectual fixation of CO2 with fast-responsive, nanomolar detection of assorted organo-contaminants in water

Highly selective capture and chemical fixation of CO2 are realized in a dual-functionalized robust MOF, which also demonstrates extremely specific, ultra-fast, and nanomolar fluorosensing of three harmful classes of organic contaminants in water.