Excellent CO2 Adsorption Capacity Research Articles

Facile One-Pot Synthesis of Zn/Mg-MOF-74 with Unsaturated Coordination Metal Centers for Efficient CO2 Adsorption and Conversion to Cyclic Carbonates.

Bimetallic metal-organic frameworks (MOFs) containing two different inorganic metal nodes exhibited enhanced properties in CO2 adsorption and catalytic conversion compared with the corresponding monometallic MOFs. In this work, the novel bimetallic Zn/Mg-MOF-74 with different ratios of Zn/Mg was synthesized successfully by a facile one-pot method. Powder X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy/transmission electron microscopy, N2/CO2 adsorption/desorption, and CO2/NH3-temperature-programmed desorption techniques thoroughly characterized the structure, morphology, and physicochemical properties of Zn/Mg-MOF-74. Besides the excellent CO2 adsorption capacity (128.3 cm3/g at 273 K and 1 bar), Zn0.75Mg0.25-MOF-74 also showed efficient catalytic activity for the cycloaddition reaction of CO2 and epoxides to cyclic carbonates with outstanding yield and selectivity all over 99% under solvent-free and mild conditions (60 °C, 0.8 MPa), outperforming the mechanical combination of Zn-MOF-74 and Mg-MOF-74 with the same metal contents, indicating the synergistic effect of two adjacent metals in bimetallic MOF-74. In addition, the Zn0.75Mg0.25-MOF-74 catalyst could be recycled for at least five runs and possess good versatility to various substrates. Finally, a feasible mechanism of the catalytic reaction was proposed. Thanks to the high surface area, affinity toward CO2, and accessibility of multiple active sites of the unsaturated metal centers as active Lewis acid sites and O atoms from Zn-O and Mg-O as Lewis basic sites, efficient chemical fixation of CO2 to cyclic carbonates was obtained over the Zn0.75Mg0.25-MOF-74 catalyst. The present facile synthesis and application of a robust bimetallic MOF catalyst offered a competitive avenue for the integration of CO2 adsorption and CO2 catalytic conversion.

CO2 adsorption performance of nitrogen-doped porous carbon derived from licorice residue by hydrothermal treatment

For high-value and environmentally friendly utilization of industrial herbal waste, a series of licorice residue-derived porous carbons were prepared with nitrogen-doped hydrothermal carbonization and KOH activation. The N-doped porous carbon activated at 600 °C exhibited excellent CO2 adsorption capacity (6.43 mmol/g at 0 °C and 1 bar, 3.89 mmol/g at 25 °C and 1 bar), high CO2/N2 selectivity (21.3), and high initial isosteric adsorption heat (28.7 kJ/mol). The excellent CO2 adsorption of the sorbent can be ascribed to its high microporosity and nitrogen content. At 0 °C and 1 bar, the ultramicropore volume below 0.7 nm contributes almost equally with the N content. However, the N content plays a dominative role at higher temperature or lower pressure. N content, especially N-5 content, performs a sound correlation with the CO2 adsorption capacity under ambient condition.

Controllable Synthesis of 1, 3, 5-tris (1H-benzo[d]imidazole-2-yl) Benzene-Based MOFs

The growing interest in metal–organic frameworks (MOFs) in both industrial and scientific circles has increased in the last twenty years, owing to their crystallinity, structural versatility, and controlled porosity. In this study, we present three novel MOFs obtained from the 1, 3, 5-tris (1H-benzo[d]imidazole-2-yl) benzene (TIBM) organic linker. The formed TIBM crystal powders were characterized by scanning electron microscopy (SEM) to estimate the morphology of the particles, powder X-ray diffraction (XRD) to confirm the crystal structure, Brunauer–Emmett–Teller (BET) method for structural analysis, and thermogravimetric measurements to examine the thermal stability. The TIBM-Cu MOF showed excellent CO2 (3.60 mmol/g) adsorption capacity at 1 bar and 298 K, because of the open Cu site, compared to TIBM-Cr (1.6 mmol/g) and TIBM-Al (2.1 mmol/g). Additionally, due to the high porosity (0.3–1.5 nm), TIBM-Cu MOF showed a considerable CO2/N2 selectivity (53) compared to TIBM-Al (35) and TIBM-Cr (10).

Nitrogen and sulfur co-doped porous carbons from polyacrylonitrile fibers for CO2 adsorption

BackgroundsAdsorption by adsorbents is accepted as a promising technology that can efficiently separate CO2 from flue gas. Optimal adsorption performance can be obtained by specific solid adsorbents with excellent CO2 adsorption capacity. MethodsIn this work, N, S co-doped porous carbons were synthesized from polyacrylonitrile fiber by a facile synthesis process i.e. hydrothermal treatment followed by KOH activation. N, S enriched hydrochar was obtained after hydrothermal treatment of polyacrylonitrile fiber and ammonium sulfide. Further KOH activation of hydrochar obtained N, S co-doped carbons with advanced porous structure. Significant findingsThis series of sorbents has the highest CO2 uptake of 3.37 and 5.23 mmol g−1 at 1 bar, 25 °C and 0 °C, respectively. Detailed investigation revealed that the mutual effects of narrow microporostiy, N and S content are responsible for the CO2 uptake of these adsorbents. Additionally, these adsorbents also show various good CO2 capture properties such as excellent recyclability, reasonable CO2/N2 selectivity, moderate heat of adsorption, fast adsorption kinetics, and good dynamic adsorption capacity. These findings suggest that N, S co-doped porous carbons derived from polyacrylonitrile fiber are potential promising sorbents for CO2 capture.

Excellent Electrochemical Performance of La0.3Sr0.7Fe0.9Ti0.1O3-δ as a Symmetric Electrode for Solid Oxide Cells.

Solid oxide cells (SOCs) can switch between fuel cell and electrolysis cell modes, which alleviate environmental and energy problems. In this study, the La0.3Sr0.7Fe0.9Ti0.1O3-δ (LSFTi 91) perovskite is innovatively used as a symmetric electrode for solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs). LSFTi 91 exhibits a pure perovskite phase in both oxidizing and reducing atmospheres, and the maximum conductivity in air and 5% H2/Ar is 150 and 1.1 S cm-1, respectively, which meets the requirement of the symmetric electrode. The polarization resistance (Rp) at 1.5 V is as low as 0.09 Ω cm2 in the SOEC mode due to the excellent CO2 adsorption capacity. The current density can reach 1.9 A cm-2 at 1.5 V and 800 °C, which is the highest electrolytic performance in the reported single-phase electrodes. LSFTi 91 also exhibits eminent oxygen reduction reaction and hydrogen oxidation reaction (ORR and HOR) activities, with Rp of 0.022 and 0.15 Ω cm2 in air and wet H2, respectively. The peak power density of SOFC could reach 847 mW cm-2 at 800 °C. In addition, good reversibility is confirmed in the cyclic operation of SOFC and SOEC.

In situ simultaneous chemical activation and exfoliation of carbon quantum dots for atmospheric adsorption of H2S and CO2 at room temperature

Herein, novel nitrogen-doped nanoporous carbons possessing 2.63 at.% N and high porosity were prepared using nitrogen-rich carbon quantum dots (N-CQDs) via a facile chemical activation. To this end, after performing the hydrothermal process on the raw materials, chemical activation was carried out by various KOH/N-CQDs ratios (2:1 to –4:1), resulting in unique micro-mesoporous structures (i.e., HNAC samples). In this approach, a large surface area (1477 m2g−1) and pore volume (1.05 cm3g−1) were obtained, where the micropore volume was increased by decreasing the KOH/N-CQDs ratio, activation time and augmenting the activation temperature, that caused considerable adsorption at 1 bar. It is worth mentioning that mesopores could be generated by condition optimization that led to higher adsorption at high pressure. Due to their large surface area and high nitrogen loading, the HNAC samples demonstrated excellent H2S and CO2 adsorption capacity at ambient conditions (9.28 mmolg−1 for H2S and 4.28 mmolg−1 for CO2 at 1 bar and 25 °C) and at higher pressures (18.0 mmolg−1 for H2S and 6.20 mmolg−1 for CO2 at 10 bar and 25 °C). According to the significant performance of the prepared nanosorbents along with stable cyclic adsorption-desorption performance, the HNACs are proposed as promising adsorbents with outstanding adsorption.

Selective CO2 adsorption using N-rich porous carbon derived from KOH-activated polyaniline

The adsorption of pure gases of carbon dioxide, methane and nitrogen was examined on nitrogen-doped porous carbon (NDC) prepared from polyaniline (PANI) as precursor by chemical activation with KOH (T=650o, IR=2, t=1 h) to determine the potential for the separation of CO2 gas from flue gas or natural gas. Adsorption equilibrium of all gases was determined in a temperature range of 298–318 K and pressure up to 14 bar. Results demonstrated an excellent CO2 adsorption capacity of 3.09 mmol·g−1 owing to high CO2 interaction affinity with NDC surface compared to CH4 (1.43 mmol·g−1) and N2 (0.64 mmol·g−1) under ambient condition (298 K and 1 bar). The ideal adsorbed solution theory (IAST) was used to determine the adsorption selectivity of NDC for CO2/CH4 and CO2/N2 mixtures at different compositions. The NDC had CO2/CH4 (4.42 and 4.08 for CO2/CH4=10/90 and 50/50, respectively) and CO2/N2 (12.81 and 12.08 for CO2/N2=15/85 and 50/50, respectively) IAST selectivity at temperature of 298 K and pressure of 1bar. The moderate CO2 adsorption enthalpy indicates that N-doped activated carbon is a promising material in gas separation such as natural gas and flue gas processing.

Design of amine-functionalized layered double oxide nanosheets with efficient CO2 capture capacities from ambient air, ultrafast kinetics, and promising stability

Recently, the Innovation Team of Energy-Water-Air (ITEWA) from Shanghai Jiao Tong University has carried out researches on direct air capture of CO2. A new family of amine functionalized DAC adsorbent was reported by impregnating branched polyethyleneimine onto mixed metal oxide nanosheets, which exhibits excellent CO2 adsorption capacity (2.27 mmol/g) and kinetics (1.1 mmol/g∙h) under 400 ppm CO2 as well as good thermal stability and hydrothermal stability with almost no performance degradation after 20 adsorption cycles (DOI: 10.1039/D0TA05079B). On this basis, a three-step steam-assisted temperature vacuum swing adsorption (S-TVSA) cycle was designed for DAC (DOI: 10.1016/j.rser.2020.110651). Simulation results show that the S-TVSA cycle could capture CO2 at a rate of 4.45 mol/kg·day. By using novel adsorbents with better adsorption capacities and kinetics, the capture rate can be further increased by 280% and the energy consumption reduced to 32.8%.

Development of Boron-Doped Mesoporous Carbon Materials for Use in CO2 Capture and Electrochemical Generation of H2O2.

Mesoporous carbon materials have been increasingly studied due to their large specific surface area and good chemical stability. Optimizing their functionality through a doping modification can broaden their application in many fields. Herein, a series of B-doped mesoporous carbon materials are prepared by a convenient hydrothermal synthesis using F127 as the template and boric acid as the boron source. The whole material preparation process meets the requirements of green chemistry. Notably, the prepared carbon materials not only exhibit good electrocatalytic oxygen reduction to hydrogen peroxide in alkaline media but also have an excellent CO2 adsorption capacity (up to 121.34 mg/g) at 303 K and atmospheric pressure. These results show that the prepared samples can be utilized as multifunctional materials for handling a variety of environmental issues.

Constructing Hierarchically Porous N-Doped Carbons Derived from Poly(ionic liquids) with the Multifunctional Fe-Based Template for CO2 Adsorption.

Nitrogen-doped hierarchical porous carbons with a rich pore structure were prepared via direct carbonization of the poly(ionic liquid) (PIL)/potassium ferricyanide compound. Thereinto, the bisvinylimidazolium-based PIL was a desirable carbon source, and potassium ferricyanide as a multifunctional Fe-based template, could not only serve as the pore-forming agent, including metallic components (Fe and Fe3C), potassium ions (etching carbon framework during carbonization), and gas generated during the pyrolysis process, but also introduce the N atoms to porous carbons, which were in favor of CO2 capture. Moreover, the hierarchically porous carbon NDPC-1-800 (NDPC, nitrogen-doped porous carbon) had taken advantage of the highest specific surface area, exhibiting an excellent CO2 adsorption capacity and selectivity compared with NDC-800 (NDC, nitrogen-doped carbon) directly carbonized from the pure PIL. Furthermore, its hierarchical porous architectures played an important part in the process of CO2 capture, which was described briefly as follows: the synergistic effect of mesopores and micropores could accelerate the CO2 molecules’ transportation and storage. Meanwhile, the appropriate microporous size distribution of NDPC-1-800 was conducive to enhancing CO2/N2 selectivity. This study was intended to open up a new pathway for designing N-doped porous carbons combining both PILs and the multifunctional Fe-based template potassium ferricyanide with wonderful gas adsorption and separation performance.

Comparison of micro‐ and nano‐sized CuBTC particles on the CO2/CH4 separation performance of PEBA mixed matrix membranes

AbstractBACKGROUNDCopper‐benzene‐1, 3, 5‐tricarboxylic acid (CuBTC) is a pre‐eminent member of the metal–organic framework material family with excellent CO2 adsorption capacity and size‐sieving characteristics for CO2/methane (CH4) separation. Although a few reports have addressed the use of micro‐sized CuBTC particles in mixed matrix membranes (MMMs), the application of nano‐sized particles has not yet been explored.RESULTSMicro‐sized and nano‐sized CuBTC particles were synthesized by Cu(NO3)2·3H2O and Cu(OH)2 precursors, respectively. Mixed matrix membranes composed of 5–35 wt% CuBTC in poly (amide‐6‐b‐ethylene oxide) (PEBA) were fabricated to investigate the CO2/CH4 separation performance of the samples. Synthesized particles and membranes were characterized by X‐ray diffraction, Fourier transform infrared and field emission scanning electron microscopy techniques. Membrane separation performance was determined at different pressures of pure CO2, CH4 and N2. At 35 wt% loading of nano‐sized CuBTC, CO2 permeability and CO2/CH4 selectivity were enhanced to 178.9 Barrer and 34.6; 80.3% and 13.8% higher than those of pristine polymer, respectively. The corresponding results for micro‐sized CuBTC were 138.9 Barrer and 33.9. A mixed gas permeation test carried out on a mixture of CO2‐CH4 (10:90 mol%) at 12 bar showed the best separation performance at 25 wt% loading of nano‐sized CuBTC with CO2 permeability of 92.6 Barrer and CO2/CH4 selectivity of 23.1.CONCLUSIONFiller size had a great impact on the MMM separation performance. As a result of the nano‐sizing of CuBTC particles, higher CO2 permeability and CO2/CH4 selectivity could be obtained because of the uniform dispersion of the filler in the matrix and higher interface area/volume. © 2020 Society of Chemical Industry

Excellent CO2 adsorption performance of nitrogen-doped waste biocarbon prepared with different activators

A series of N-doped CO2 adsorbents were prepared by using waste walnut shell as the raw material, urea as nitrogen source, H3PO4 as a pretreatment agent and KOH, K2CO3 and ZnCl2 as the activators. Result indicates that both the pore structure and nitrogen content of the adsorbent together affect the CO2 adsorption capacity. HAC-850-KOH showed excellent CO2 adsorption capacity (5.13 mmol/g) at 0 °C and atmospheric pressure probably because of its large specific surface area (SBET 2354 m2/g). HAC-750-ZnCl2 has the higher CO2 adsorption capacity (0.6 mmol/g) at 25 °C and 0.15 bar due to its highest nitrogen content (9.32 wt%). HAC-850-K2CO3 has a good selectivity of 21.5 and cycle performance may be somewhat associated with its pore structure and nitrogen content, and the initial heat of adsorption is 44 kJ/mol. The result indicates that the pore structure of the adsorbent has a great influence on the adsorption performance under high pressure; the nitrogen content of the adsorbent has a decisive influence on the adsorption performance of the adsorbent under low pressure. At the same time, the pore structure properties of the prepared adsorbent have a more significant effect on the adsorption performance at lower temperatures. This work provides an effective guide to synthesize biomass-based adsorbent for different application conditions, especially in the selection of activators.

Photocatalytic Reduction of CO2 to CO over 3D Bi2MoO6 Microspheres: Simple Synthesis, High Efficiency and Selectivity, Reaction Mechanism

It has been a promising approach for directly utilizing solar energy to convert CO2 into clean renewable chemical fuels over photocatalysts with excellent photoreactivity, CO2 adsorption capacity and reasonable redox potentials. In this work, as-synthesized 3D Bi2MoO6 microspheres with cross-stacking nanosheets via a simple hydrothermal method have been investigated for photocatalytic CO2 reduction, and characterized by XRD, UV–Vis DRS, SEM, HRTEM and BET. It was found that as-prepared samples exhibited high Bi2MoO6 purity, large specific surface area, excellent light response and CO2 adsorption capacity, achieving superior photocatalytic CO2 reduction activity and selectivity of CO yield (41.5 μmol g−1 h−1). Moreover, the photocatalytic reaction mechanism for CO2 reduction to CO over 3D Bi2MoO6 microspheres was investigated and proposed. Finally, COOH* was verified to be a key intermediate for photocatalytic CO2 reduction to CO by the analysis of in-situ FTIR. Our findings should provide excellent foundation and guidance for boosting photocatalytic CO2 conversion to CO with enhanced effective and selective ability. 3D Bi2MoO6 microspheres with cross-stacking nanosheets exhibit large specific surface area, excellent light response and CO2 adsorption capacity. COOH*, as a key reaction intermediate, can significantly reduce the activation energy of CO2.

CdSe/ZIF-8-x: synthesis and photocatalytic CO2 reduction performance.

The photocatalytic reduction of CO2 is an effective way to solve the greenhouse effect. Different kinds of materials, such as semiconductors, coordination compounds, and bioenzymes, have been widely investigated to increase the efficiency of the photocatalytic reduction of CO2. However, a high selectivity and great stability are still challenges for material scientists. Here, we report for the first time visible light photocatalytic CO2 reduction by a series of CdSe/ZIF-8 nanocomposites combining the excellent CO2 adsorption capacity of ZIF-8 and the narrow energy gap of CdSe quantum dots (QDs). The composites show a higher catalytic performance than those of the pure components. Among CdSe/ZIF-8-x (x = nCdSe/nZIF-8), the highest yield (42.317 μmol g−1) for reducing CO2 to CO in 12 h, was obtained using nanocomposites with a ratio of 0.42 (nCdSe/nZIF-8) within the range of investigation.

Structure-performance relationships of magnesium-based CO2 adsorbents prepared with different methods

Magnesium-based adsorbents present great potential in separating CO2 from flue gas stream. To satisfy the requirement of efficient CO2 capture, it is imperative to select suitable methods for preparing MgO adsorbents with good physicochemical properties. In this study, MgO adsorbents were prepared with different methods using MgCl2·6H2O as magnesium precursor, and the effect of synthesis method on their structure-performance relationships were investigated. It is found that MgO adsorbents prepared with different methods exhibited varied physicochemical properties, and these were associated with their diverse CO2 adsorption capacities. Amongst the different MgO adsorbents, the sample prepared with the solid-state chemical reaction method (MgO-SR) featured good textural properties (high specific surface area and total pore volume of 100.03 m2/g and 0.67 cm3/g), preferable surface morphology (sheet-like structure with reduced layer diffusion resistance) and excellent CO2 adsorption capacity (2.39 mmol CO2/g). The solid-state chemical reaction method endowed the adsorbent with abundant surface basic active sites, and CO2 molecules interacted with the weak sites (OH group), medium sites (Mg-O pairs) and strong sites (O2−) to form stable bicarbonate, bidentate and unidentate carbonates. The experimental CO2 uptakes were in good agreement with the values predicted by the Avrami fractional kinetic model. Physical adsorption and chemisorption coexisted in the CO2 adsorption process and the chemisorption sites played a dominant role. The approach enlightens the facile fabrication of cost-effective MgO adsorbents from waste precursors for large-scale CO2 capture applications.

A microwave method for the rapid crystallization of UTSA-16 with improved performance for CO2 capture

Microwave (MW) irradiation is a simple and effective nonconventional heating method and is well-known in the field of metal-organic framework synthesis. In this paper, we report, a rapid microwave-assisted method for the synthesis of a UTSA-16 metal-organic framework. This process noticeably reduces the synthesis time from the 48 h required in traditional synthesis to 4 h. The synthesis of UTSA-16, whose formation was confirmed by X-ray diffraction analysis, was optimized by varying the synthesis time from 0.5 to 8 h. The UTSA-16 prepared with a reaction time of 4 h (4 h-UTSA-16) showed excellent CO2 adsorption capacity of 5.5 mmol/g at 298 K and 1 bar with a CO2/N2 sorption selectivity of 104, which is even higher than those reported for UTSA-16 samples prepared by solvothermal methods. The stability of UTSA-16 in humid air and acid gases was investigated by exposing it to humid air, as well as SO2 and NO2 gases, for 6 days. The UTSA-16 was very stable, showing no changes in the CO2 capture capacity and FTIR spectra after exposure to NO2 in humid air.

SBA-15/ACF hierarchical pore structure material with enhanced CO2 capture ability

SBA-15/ACF with a hierarchical pore structure was produced by the modified hydrothermal synthesis method using SBA-15 and activated carbon fiber (ACF). As the factors related to the pore structures, the optimized temperature of removing template at 300 °C and materials ratio of 1:50 made the SBA-15/ACF with a high specific surface area of 1468 m2 g−1 and total pore volume of 0.7519 cm3 g−1. Compared with the existing adsorbents, the hierarchical pore structure of the composite resulted a good CO2 adsorption capacity of 4.49 mmol g−1. The excellent CO2 adsorption capacity demonstrated that the SBA-15/ACF composite could be a promising adsorbent in the CO2 capture field.

Layer-by-layer self-assembly of sodium tripolyphosphate/chitosan composites on mesoporous alumina for CO2 adsorption

Abstract We report the synthesis of mesoporous alumina (MA)-supported sodium tripolyphosphate (STPP)/chitosan (Ch) composite (denoted as MA@STPP/Ch) by a layer-by-layer self-assembly method. The multilayered MA@STPP/Ch is nontoxic and shows excellent CO2 adsorption capacity (maximum: 278.96 mg g−1 at 50 °C) and reusability, better than that of MA (97.24 mg g−1 at 50 °C). The enhanced CO2 adsorption could be ascribed to the synergism between porous structure and functional groups of Ch.

The most advanced synthesis and a wide range of applications of MOF-74 and its derivatives

Abstract This review summarizes the latest synthesis methods, characterization and corresponding applications of MOF-74 and its derivatives in recent years. Metal–organic frameworks (MOFs) are nanomaterials with many attractive advantages, such as good stability, large specific surface area and large apertures, which make them receive considerable attention. Among them, MOF-74 is a particularly outstanding one attribute to its excellent CO2 adsorption capacity. MOF-74 can be synthesized directly from a metal oxide and without bulk solvent, which not only saves a lot of time and money, but also is more ecological. The mesopores in MOF-74 can be adjusted to as large as 15 nm stably at room temperature. And characterization results show MOF-74 possesses good hydrolysis stability, highly stable structure, gas adsorption capacity, catalytic activity and so on. In addition, multifarious synthetic materials with additional functionality can be obtained by properly combining MOF-74 with other components. Therefore, MOF-74 has great potential and has aroused great enthusiasm for research in many aspects, such as gas adsorption, separation, and catalysis and so on.

Amine-impregnated carbon aerogels with ultra-high pore volume synthesized by pH adjusting for efficient CO2 Capture

Carbon aerogels with ultra-high pore volume and meso/macro pores were successfully synthesized by using silica hard templating combined sol–gel method by controlling the pH value of the initial reaction solution. High loadings (65–80 wt%) of TEPA (tetraethylenepentamine) and PEI (polyethyleneimine) were impregnated into CA with a high pore volume of 5.7 cm3/g for CO2 adsorption, respectively. The effects of amine loading, CO2 concentration, adsorption temperature, and moisture on the CO2 adsorption performance of the amine-loaded CA sorbents were comparatively investigated. The results showed that the CA with ultra-high pore volume enabled excellent CO2 adsorption capacity and fast kinetics (5.93 mmol/g and 4.70 mmol/g within 2.5 min for the case of TEPA and PEI respectively at 75 °C under 10% dry CO2). The sorbents exhibited good recycle-ability both in dry and humid conditions. Under humid conditions, the diffusion resistance of the sorbents at the initial stage of CO2 adsorption was observed. This study suggests that CA with large pore size could be utilized as promising amine sorbent for post-combustion CO2 capture.