CO2 Capacity Research Articles

Adsorption of CO2 and H2 on the polymer-based membrane from High-density Polyethylene (HDPE) Plastic

High-density polyethylene (HDPE), a widely used polymer globally, notably found in plastic bags, presents an environmental concern due to its non-biodegradable nature. Transforming non-biodegradable HDPE waste into a valuable resource presents a formidable ecological challenge. This research aims to study CO2 and H2 gases toward HDPE-based membranes through the adsorption process with pressure and temperature variation. The highest CO2 and H2 adsorption capacities of 14.19 mmol.g−1 (62.43 %wt) and 18.04 mmol.g−1 (3.61 %wt) were obtained by pressure feeding 3 bar at 30°C. The adsorption capacity decrease as the temperature increase. At an adsorption temperature of 50°C, the adsorption capacity of CO2 and H2 decrease, respectively by 75.86 % and 69.81 %. The adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, and intraparticle diffusion models. The kinetic study shows that adsorption at 30°C follows the pseudo-second order. The adsorption at elevated temperatures reveals the intraparticle diffusion mechanism, indicating that the gas is adsorbed directly into the polymer matrix. Thermodynamic results include enthalpy of adsorption (ΔH), standard entropy of adsorption (ΔS), energy Gibbs (ΔG), and energy activation (Ea). ΔH CO2 and H2 are -22.339 and -23.654 kJ mol−1, respectively, which indicates that the process is exothermic and physisorption. The ΔS value shows that the irregularity and randomness of gas movement during the adsorption process, with the respective values for CO2 and H2 are -0.069 and -0.072 kJ mol−1K−1, respectively. ΔG for adsorption of CO2 and H2 with increasing temperature becomes less spontaneous, which results in decreased adsorption capacity. Ea of CO2 is greater than H2, so the adsorption capacity of CO2 is smaller than H2. The thermodynamic study shows that the adsorption process is preferable at lower temperatures.

High coking resistance of Ni/A2Ti2O7 catalysts via modulating the A site of A2Ti2O7 (A = La, Gd) for dry reforming of methane

Ni based catalysts are currently the most investigated for dry reforming of methane (DRM) due to the advantages in intrinsic activity and cost. However, due to carbon deposition, the questionable durability greatly limits its practical application in the industry. Herein, Gd-doped Ni-La2Ti2O7 and La-doped Ni-Gd2Ti2O7 catalysts were prepared by modulating the A site of the A2Ti2O7 structure. Moderate A site doping tunes the electronic properties of the A2Ti2O7, which would not only significantly enhance the activation ability of C–H bonds of CH4, but also enhance the adsorption capacity of CO2, ultimately affecting the catalytic performance of Ni/A2Ti2O7 for the DRM. Among the modified catalysts, 2 % Gd doped Ni-La2Ti2O7 exhibited excellent stability and maintained CH4 and CO2 conversion at 70.8 % and 86.6 %, respectively, for 200 h at 800 °C with negligible carbon deposition. The fundamental reason for A site doping is that it can make the catalyst produce more surface adsorbed oxygen species, which could accelerate the elimination of deposited carbon.

Postsynthetically Modified Alkoxide-Exchanged Ni2(OR)2BTDD: Synergistic Interactions of CO2 with Open Metal Sites and Functional Groups.

Postsynthetic modifications (PSMs) of metal-organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni2Cl2BTDD (BTDD=bis (1H-1,2,3,-triazolo [4,5-b],-[4',5'-i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X-ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide-exchanged MOFs showed CO2 uptakes superior to the pristine MOF. Remarkably, the tert-butoxide-substituted Ni_T exhibited a nearly threefold and twofold increase in CO2 uptake compared to Ni2Cl2BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO2 interacts with the OMS and the surrounding methyl groups of tert-butoxide groups, which is responsible for the enhanced CO2 capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS-incorporating MOF platform through bridging ligand exchange.

Postsynthetically Modified Alkoxide‐Exchanged Ni2(OR)2BTDD: Synergistic Interactions of CO2 with Open Metal Sites and Functional Groups

AbstractPostsynthetic modifications (PSMs) of metal–organic frameworks (MOFs) play a crucial role in enhancing material performance through open metal site (OMS) functionalization or ligand exchange. However, a significant challenge persists in preserving open metal sites during ligand exchange, as these sites are inherently bound by incoming ligands. In this study, for the first time, we introduced alkoxides by exchanging bridging chloride in Ni2Cl2BTDD (BTDD=bis (1H‐1,2,3,–triazolo [4,5‐b],–[4′,5′‐i]) dibenzo[1,4]dioxin) through PSM. Rietveld refinement of synchrotron X‐ray diffraction data indicated that the alkoxide oxygen atom bridges Ni(II) centers while the OMSs of the MOF are preserved. Due to the synergy of the existing OMS and introduced functional group, the alkoxide‐exchanged MOFs showed CO2 uptakes superior to the pristine MOF. Remarkably, the tert‐butoxide‐substituted Ni_T exhibited a nearly threefold and twofold increase in CO2 uptake compared to Ni2Cl2BTDD at 0.15 and 1 bar, respectively, as well as high water stability relative to the other exchanged frameworks. Furthermore, the Grand Canonical Monte Carlo simulations for Ni_T suggested that CO2 interacts with the OMS and the surrounding methyl groups of tert‐butoxide groups, which is responsible for the enhanced CO2 capacity. This work provides a facile and unique synthetic strategy for realizing a desirable OMS‐incorporating MOF platform through bridging ligand exchange.

Designed imidazolium-based ionic liquids to capture carbon dioxide from natural gas

Natural gas is considered one of the most appealing fossil fuels in the world's energy supply nowadays, and it is primarily recognized as a clean energy source. However, the removal of pollutants from NG, particularly carbon dioxide (CO2), requires complex treatment strategies, significantly influencing its production. Consequently, the appealing properties of ionic liquids (ILs) make them interesting eco-friendly candidates for capturing CO2 from natural gas. In this work, a series of novel functionalized ILs (IL-Br, IL-BF4, and IL-PF6) were synthesized and characterized via a variety of analysis tools, including FT-IR, NMR, and thermal gravimetric analysis. Highly efficient capture of CO2 from natural gas was investigated at ambient temperature and was successfully achieved with the synthesized ILs. IL-PF6 recorded the highest capture CO2 capacity from the natural gas stream, which reached up to 94 % in only 5 min as a retention time. The experimental results revealed that each gram of IL-PF6, IL-BF4, and IL-Br could capture 2.02, 1.23, and 1.18 mmol of CO2, respectively. The used ILs were reused three times without any significant reduction in their capturing performance, which enhances their potential for eco-friendly and cost-saving issues. The CO2 capture efficiency of the used ILs was verified theoretically using the DFT method and Monte Carlo simulations (MCs). The quantum study matches with the experimental results, which confirmed the CO2 capture efficiency in the order of IL-PF6 > IL-BF4 > IL-Br.

Experimental study on the performance of a highly efficient NE‐1 absorbent for CO2 capture

AbstractCO2 capture by absorption and stripping with aqueous amine is a well‐understood and widely used technology. However, drawbacks still exist in the practical applications, such as high energy consumption and easy degradation of the absorbents during the desorption process. In this paper, a novel NE‐1 absorbent was developed, and its suitable operating conditions were determined: concentration (45 wt.%), absorption temperature (40 °C), and desorption temperature (100 °C). The NE‐1 absorbent exhibits a high CO2 absorption capacity of 3.73 mol/kg, 1.33 times that of 30% monoethanolamine (MEA). After optimizing with carbamide as a corrosion inhibitor, 45% NE‐1a1 may attain an effective CO2 capacity of 2.5 mol/kg and over 70% desorption rate in five cycles, demonstrating excellent cycling stability performance. The research results have significant implications for developing an efficient and stable commercial carbon capture solvent and promoting the development of carbon reduction technologies. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

S-scheme heterojunction Cu-porphyrin/TiO2 nanosheets with highly efficient photocatalytic reduction of CO2 in ambient air

Directly capturing CO2 in ambient air and converting it into value-added fuels using photocatalysis is a potentially valuable technology. In this study, Cu-porphyrin (tetrakis-carboxyphenyl porphyrin copper, CuTCPP) was innovatively anchored on the surface of TiO2 (titanium dioxide) nanosheets to form an S-scheme heterojunction. Based on this, a photocatalytic reaction system for stably converting CO2 in ambient air into value-added fuels at the gas–solid interface was constructed without addition of sacrificial agents and alkaline liquids. Under the illumination of visible light and sunlight, the evolution rate of CO is 56 μmol·g−1·h−1 and 73 μmol·g−1·h−1, respectively, with a potential CO2 conversion rate of 35.8 % and 50.4 %. The enhanced of photocatalytic performance is attributed to the introduction of CuTCPP, which provides additional active sites, significantly improves capture capacity of CO2 and the utilization of electrons. Additionally, the formation of S-scheme heterojunction expands the redox range and improves the separation efficiency of photo-generated charges.

Developing Multifunctional Fe-Based Catalysts for the Direct Hydrogenation of CO2 in Power Plant Flue Gas to Light Olefins

The hydrogenation of carbon dioxide (CO2) to produce light olefins is one of the most promising ways to utilize CO2 in power plant flue gas. However, the low concentration of CO2 (~10%) and the existence of water steam in the flue gas pose great challenges for the catalyst design. To address these problems, we introduced a Mg promoter and hydrophobic component into the Fe-based catalyst to improve the CO2 adsorption capacity and weaken the negative effects of water. The yield of light olefins on an optimized multifunctional Fe-based catalyst increased by 37% in low-concentration CO2 hydrogenation with water steam. A variety of characterizations proved that the Mg promoter played critical roles in regulating the adsorption capacity of CO2, increasing the surface electron density of Fe species, and promoting the formation of iron carbide active sites. The hydrophobic component mainly contributed to constraining the oxidation of iron carbides via water steam. It benefited from the rational design of the catalyst, showing how our multifunctional Fe-based catalyst has great potential for practical application in CO2 utilization.

MOF‐derived 1D/3D N‐doped porous carbon for spatially confined electrochemical CO2 reduction to adjustable syngas

AbstractElectrochemical reduction of CO2 to syngas (CO and H2) offers an efficient way to mitigate carbon emissions and store intermittent renewable energy in chemicals. Herein, the hierarchical one‐dimensional/three‐dimensional nitrogen‐doped porous carbon (1D/3D NPC) is prepared by carbonizing the composite of Zn‐MOF‐74 crystals in situ grown on a commercial melamine sponge (MS), for electrochemical CO2 reduction reaction (CO2RR). The 1D/3D NPC exhibits a high CO/H2 ratio (5.06) and CO yield (31 mmol g−1 h−1) at −0.55 V, which are 13.7 times and 21.4 times those of 1D porous carbon (derived from Zn‐MOF‐74) and N‐doped carbon (carbonized by MS), respectively. This is attributed to the unique spatial environment of 1D/3D NPC, which increases the adsorption capacity of CO2 and promotes electron transfer from the 3D N‐doped carbon framework to 1D carbon, improving the reaction kinetics of CO2RR. Experimental results and charge density difference plots indicate that the active site of CO2RR is the positively charged carbon atom adjacent to graphitic N on 1D carbon and the active site of HER is the pyridinic N on 1D carbon. The presence of pyridinic N and pyrrolic N reduces the number of electron transfer, decreasing the reaction kinetics and the activity of CO2RR. The CO/H2 ratio is related to the distribution of N species and the specific surface area, which are determined by the degree of spatial confinement effect. The CO/H2 ratios can be regulated by adjusting the carbonization temperature to adjust the degree of spatial confinement effect. Given the low cost of feedstock and easy strategy, 1D/3D NPC catalysts have great potential for industrial application.

The influence of Mg/Al molar ratio on the performance of CuMgAl-x catalysts for CO2 hydrogenation to methanol.

The CuMgAl-x catalysts derived from hydrotalcite precursors with different Mg/Al molar ratios were synthesized and applied to CO2 hydrogenation to methanol reaction. In this study, the effects of Mg/Al molar ratio on the structure and surface properties of CuMgAl-x catalysts were investigated by XRD, N2 adsorption-desorption, SEM, TEM, H2-TPR, CO2-TPD, XPS, and in situ DRIFTS characterization methods. The results showed that an appropriate Mg/Al molar ratio can enhance the Cu-MgO interaction, increasing the basic sites and obtaining suitable acid sites. The dispersion of active Cu on the CuMgAl-x catalysts can be improved by strong Cu-MgO interaction, which enhances the adsorption capacity of CO2 and makes H2 activation easier, accelerates the conversion of intermediate species CO3 * and HCO3 *to HCOO*, and facilitates further conversion to CH3O* and CH3OH. The strong interaction between Cu and MgO was conducive to the formation of Cu+, which can inhibit the desorption of CO in the reverse water gas shift reaction. The CuMgAl-3 catalyst showed the highest CO2 Conversion rate (14.3%), methanol selectivity (94.5%), and STY of methanol (419.3g⋅kgcat. -1⋅h-1) at 240°C and 2.5MPa. The results obtained in this paper can provide a new idea for the design of high-performance catalysts for CO2 hydrogenation to methanol.

Efficient carbon dioxide capture from flue gas and natural gas by a robust metal–organic framework with record selectivity and excellent granulation performance

The design of porous materials for CO2 capture from flue gas and natural gas is highly demanded. However, it is challenging to target materials that combine high CO2 capacity and CO2 selectivity. In this work, we report a robust metal–organic framework (MOF) Zn-ox-mtz with one dimensional channels and narrow windows for excellent CO2 capture from CO2/N2 (simulated flue gas) and CO2/CH4 (simulated natural gas) with high selectivity. Zn-ox-mtz exhibits a high CO2 capacity (58.0 STP cm3 g−1 at 15 kPa), excellent CO2/N2 (15/85, S > 106) and CO2/CH4 (50/50, S > 105) selectivity and good chemical stability. In addition, the practical separation performance is demonstrated by breakthrough experiments under various process conditions. A efficient separation is achieved with the impressive CO2 capacity of 2.60 ± 0.12 mmol g−1 at 298 K. Importantly, the outstanding performance is sustained under high humidity. The molecular sieving mechanism investigated by theoretical calculations indicated that CO2 with small molecular size is tightly trapped by multiple C = O···H-C hydrogen bonding and O = C···O forces in the cavity while CH4 and N2 with larger molecular size display overlarge energy barrier to cross the contract pore windows. Moreover, the granulation of Zn-ox-mtz by hydroxypropyl cellulose is realized with high MOF loading (93.8 %) and the granulated Zn-ox-mtz beads retained the excellent CO2/N2 and CO2/CH4 separation performance.

Exploring NH3 combustion in environments with CO2 and H2O via reactive molecular dynamics

In existing power units such as internal combustion engines and gas turbines, the combustion of ammonia mixed with hydrocarbon fuels can effectively enhance the combustion intensity of ammonia. In the duel-fuel combustion scenario, the effect mechanism of the main components of combustion exhaust gas i.e., CO2 and H2O on ammonia combustion is still unclear and needs to be studied. Therefore, this paper uses reactive molecular dynamics simulations to study the combustion and emission processes of ammonia in environments with CO2 and H2O. The effects of the diverse gas environments (N2/O2, O2/CO2, and O2/CO2/H2O environments), high CO2 levels, varying H2O proportions, and O2 concentrations on ammonia combustion and emission were systematically explored. It was found that ammonia consumption was accelerated in the O2/CO2/H2O environments compared to N2/O2 environments, resulting in more NH2, H2, and H2O production. The effect of high CO2 concentration on ammonia oxidation was mainly related to temperature. The simulations found that the high CO2 concentration inhibited ammonia consumption at T < 2800K while enhancing it at T ⩾ 2800K. In addition, the high CO2 concentration could inhibit NO production under stoichiometric conditions but promote the conversion of nitrogen-containing intermediates to NO with the oxidizing capacity of CO2 enhanced significantly under extremely high temperature conditions. It was found that the increasing content of H2O molecules in the environment promoted NO production and inhibited CO production under stoichiometric conditions. In addition, the reaction paths for the conversion of HNO and HNO2 molecules into NO molecules were significantly enhanced with increasing H2O concentration. The increase in oxygen concentration can promote OH radical production and NO formation at high temperatures.

Modulated synthesis of stoichiometric and sub-stoichiometric two-dimensional covalent organic frameworks for enhanced ethylene purification

Controlled synthesis of two-dimensional covalent organic frameworks (2D COFs), including stoichiometric and sub-stoichiometric variations, is a topic of growing interest due to its potential in gas separation applications. In this study, we successfully synthesized three distinct 2D COFs by carefully adjusting solvent compositions and monomer ratios during the synthesis of [4 + 4] type COFs. These included a stoichiometric [4 + 4] type COF and two sub-stoichiometric [4 + 2] type COFs, featuring unreacted amino or formyl groups. The resulting COFs exhibit different gas adsorption and separation properties. Specifically, sub-stoichiometric COF-DA with residual amino groups shows comparable adsorption capacity for C2H2, C2H4, and CO2 to stoichiometric COF-DAPy. In contrast, sub-stoichiometric COF-Py with residual formyl groups displays enhanced adsorption selectivity for C2H2/C2H4 and C2H2/CO2 separation, with the C2H2/C2H4 selectivity being the highest among reported COFs, attributed to increased pore polarity resulting from the presence of formyl groups. This study not only offers an additional example of sub-stoichiometric COF synthesis but also advocates for further exploration of sub-stoichiometric COF materials, particularly in the field of gas adsorption and separation.

Assisting Bi2Fe4O9 nanosheets with CeO2@PANACSs macro-spheres as bifunctional supporter for enhanced photocatalytic CO2 reduction

The efficient capture of CO2 molecules is a crucial step in the light-driven CO2 synthesis of high value-added products. In this work, CeO2 is embedded in polyacrylonitrile-based carbon spheres (PANACSs) via a suspension polymerization and carbonization method to synthesise CeO2@PANACSs with bifunction (CO2 adsorption and reduction ablity), and the strong oxidising capacity Bi2Fe4O9 was coupled to obtain ternary Bi2Fe4O9/CeO2@PANACSs composites with high adsorption-reduction capacity for CO2. The effective synergistic effects between Bi2Fe4O9 and CeO2@PANACSs realize that the CO yield of ternary hybrid photocatalyst can reach as high as 256.1 μmol g−1 for 10 h, approximately 19.55 times, 1.45 times and 1.62 times higher than that of pristine PANACSs, Bi2Fe4O9 and CeO2, respectively. The exceptional performance of Bi2Fe4O9/CeO2@PANACSs composites is mainly attributed to the synergistic effect of the ternary system, which not only provides CO2-rich adsorption-reduction active sites but also effectively inhibits photogenerated electron-hole complexation. Meanwhile, the outer layer of Bi2Fe4O9 with its excellent oxidising capacity also provides a large amount of H* to ensure efficient hydrodeoxygenation of CO2. Finally, combined with the results of in situ fourier transform infrared spectra, a possible mechanism for the photocatalytic reduction of CO2 over ternary photocatalysts is proposed. Our finding provides a noteworthy promising strategy to construct bifunctional composite photocatalysts for achieving the high-efficient CO2 adsorption and photoreduction to CO.

Integration of physical solution and ionic liquid toward efficient phase splitting for energy-saving CO2 capture

Carbon dioxide (CO2) capture from flue gas is crucial for achieving industrial carbon neutrality. Using a biphasic solvent can significantly reduce the volume of regenerated solvent for energy-saving carbon capture. In this study, a novel strategy for biphasic solvent preparation was proposed by combining amine blends (3,3′-Diaminodipropylamine, DADPA; N-Methyldiethanolamine, MDEA) and composite agents (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, BN; sulfolane, TMS). The screened proportion of DADPA:MDEA:TMS:BN:H2O was 2:6:2:1:2 (labelled DMTB). Experimental evaluation revealed that the DMTB solvent exhibits a high CO2 capacity of 4.59 mol/L (in the 50 vol% rich phase), an efficient phase splitting rate (within 3 min) and a fast CO2 desorption rate. The dynamic phase-splitting capacity was evaluated by a quasi-two-dimensional separator, under various operational condition. The 13C NMR results indicated the formation of DADPACOO- in the CO2-saturated phase in the presence of water rather than bicarbonate while observing dissociative behaviour in MDEA and TMS. Therefore, the phase separation analysis revealed that the products of protonated amines and carbamic acid species were highly polar and preferred to dissolve in the water phase. This study provides an optional biphasic solvent with phase splitting ability for CO2 capture from flue gas.

Enhancement of N2O decomposition performance by co-doping of Ni and Y to Co3O4 catalyst

Co3O4, Y2O3-Co3O4 and NiO-Y2O3-Co3O4 samples were prepared by the simple co-precipitation method, and their N2O catalytic decomposition performance was evaluated. Experimental results disclose that the order of catalytic activity among the three catalysts is NiO-Y2O3-Co3O4 > Y2O3-Co3O4 >> Co3O4. N2O conversion over NiO-Y2O3-Co3O4 catalyst reached 100 % at 360 °C, which was 20 °C and 60 °C lower than those over Y2O3-Co3O4 and Co3O4, respectively. In addition, NiO-Y2O3-Co3O4 catalyst shows better water resistance compared with Co3O4 and Y2O3-Co3O4. Systems-based characterization techniques, it is confirm that Y and Ni were successfully doped into Co3O4, where Y was on the surface and Ni was mainly in the bulk phase. Due to the co-doping of Y and Ni, NiO-Y2O3-Co3O4 catalyst has smaller average particle size and reinforced surface alkalinity. Furthermore, the surface modification of Y enhances the electron-donating capacity of Co2+ and oxygen desorption ability, while bulk phase doping of Ni facilitates the reduction of Co3+ to Co2+ and weakens Co-O bond in Co3O4, which endow NiO-Y2O3-Co3O4 sample with lower Ea for N2O decomposition. Therefore, NiO-Y2O3-Co3O4 catalyst exhibits the best N2O catalytic decomposition performance.

ZSM-5@MOF-199 core-shell composite adsorbent: Rapid ambient synthesis and CO/CO2 adsorption

Using a hydroxy double salt intermediate, we demonstrated rapid room temperature fabrication of ZSM-5@MOF-199 core–shell sorbents. Copper chloride was compatible with the ZnO-assisted MOF growth scheme. The structural and chemical properties of the composite were fine-tuned through either the core or the shell modification, targeting a superior adsorption capacity for CO and CO2 compared to parent adsorbents. For example, the Na2S2O3-assisted MOF-199 shell reduction enriched surface Cu+ and enhanced CO adsorption capacity. Modulating the zeolite core to protonic hierarchical ZSM-5 (HZSM-5) increased CO and CO2 uptake by 20 % and 28 %, respectively. The isosteric heat of adsorption revealed that the HZSM-5 core altered surface electronic properties and influenced the CO2 adsorption performance. Thermodynamic analysis indicated that the adsorption processes involved a combination of physisorption and electrostatic interactions with an ordered arrangement of adsorbates. The core–shell sorbent can be easily tuned for selective separation of CO and CO2.

Theory-based design principles for unprecedentedly high two-level CO2 utilization of CO2-derived metal-organic frameworks

In this study, we theoretically developed a novel strategy for “two-level” CO2 utilization: the first level is “CO2 content” by directly converting CO2 into metal-organic frameworks (MOFs), and the second level is “CO2 capacity” by storing CO2 gas into their cavity. Despite its conceptual simplicity, experimental realization is rare due to technical difficulties and a lack of design principles for simultaneously maximizing CO2 content and CO2 capacity, leaving many unexplored possibilities. In this study, we designed over 1,500 hypothetical MOFs across 15 types of metal nodes combined with 14 types of newly designed CO2-derived ligands in over 40 topologies. We found that [-CO2NHNHCO2-] ligand assembled with [V2(CO2)4] node on the zeolite-like usf topology can have a large CO2 content of 50 wt%, which exceeds 31.6 wt% for the synthesized CO2-derived MOF. Grand Canonical Monte Carlo Simulation showed that the well-alignment of the paddlewheel in usf topology allows CO2 to be fully exposed to the cavity space, achieving high CO2 adsorption capacity. In addition, the fluorination of the ligand of MOFs significantly increases CO2 capacity and reaches unprecedented high CO2 utilization of up to 62 wt%. The design principles and database from this work provide opportunities and challenges for experimentalists in synthesizing new MOFs with breakthrough CO2 utilization.

A novel preparation of microporous nanosilica derived from aluminum-extracted residue of coal fly ash for highly selective CO2 adsorption

Currently, the poor adsorption performance caused by the unsatisfactory pore size seriously restricts the further development of microporous nanosilica (MS). Herein, an excellent microporous nanosilica was constructed by preparing calcium silicate hydrate (CSH) support from the aluminum-extracted residue of coal fly ash and modifying it with different activating agents (H2SO4, HNO3, HCl, CH3COOH, KOH, NaOH and Na2CO3). The results indicated that CH3COOH at 30 wt% was the optimal modifier, achieving a CO2 uptake of 1.42 mmol/g at 298 K and 1.0 bar. Then the effects of synthesis parameters including mass fraction, liquid–solid ratio, temperature, and time on the adsorption capacity of CO2 were further investigated. The obtained MSCp exhibited a high specific surface area (up to 505.71 m2/g), well-developed microporosity (0.085 cm3/g), and excellent CO2 uptake (2.12 mmol/g at 273 K, 1.41 mmol/g at 298 K). Based on the study of kinetics, isosteric heat of adsorption (Qst), and situ diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS), the adsorption mechanism of MSCp was determined to be mainly physical adsorption. Besides, the excellent CO2/CH4 selectivity of 20.91 (15/85, v/v) and 30.75 (50/50, v/v), CO2/N2 selectivity of 53.79 (15/85, v/v) and 163.76 (50/50, v/v) were obtained from MSCp at 298 K and 1.0 bar. Finally, the binary gas breakthrough experiments and eight adsorption–desorption cycles confirmed the MSCp was suitable for selective adsorption of CO2 in practical applications.

Application of lithium modified ZIF-90 in a hybrid absorption-adsorption method for carbon capture

Herein, a lithium modified Zeolitic Imidazolate Framework-90 (ZIF-90-OLi) was used in a slurry with its organic ligand Imidazole Carboxaldehyde (ICA) water, and glycol to improve the process conditions for the capture system and enhance the sorption ability. The performance of this slurry was compared to two other slurries, one based on the parent ZIF-90 nanoporous material with ICA/water/glycol and another based on ZIF-8, its organic ligand Methylimidazole (MIm) and water/glycol. The comparison to ZIF-8 was done because of its use as a ZIF of reference in carbon capture. The maximum sorption capacity for CO2 by the alkali containing slurry was 7.19 mol/L and the maximum CO2/N2 selectivity was 222.93 compared to 2.72 mol/L and 121.63 for the ZIF-8/water/glycol/mlm slurry.