CO2 Adsorption Rate Research Articles

Thermodynamics and Kinetics of CO2/CH4 Adsorption on Shale from China: Measurements and Modeling

CO2-enhanced shale gas recovery (CO2-ESGR) sequestrates anthropogenic CO2 and improves the profitability of shale gas exploitation. This work investigated the adsorption behaviors of CO2 and CH4 on shale from China at 20, 40, 60 and 80 °C. The pressure ranges for CO2 and CH4 were 1–5 and 1–15 MPa, respectively. The excess adsorbed amount of CH4 increased with increasing pressure from the beginning to the end, while the maximum excess CO2 adsorption was observed at approximately 4 MPa. The absolute average deviations (AADs) of CO2 and CH4, determined by the Langmuir + k model, were 2.12–3.10% and 0.88–1.11%, respectively. Relatively good adsorptivity for CO2 was exhibited when the pressure was less than 5 MPa, which was beneficial to the implementation of CO2-ESGR. With continuous increases in pressure, the adsorption capacity of CO2 was weaker than that of CH4, suggesting that the injected CO2 would reduce the partial pressure of CH4 for CO2-ESGR and the displacement effect would no longer be significant. In addition, the adsorption rate of CO2 was much faster than that of CH4. CO2 was more active in the competitive adsorption and it was advantageous to the efficiency of CO2-ESGR.

Polyethylenimine-Grafted HKUST-Type MOF/PolyHIPE Porous Composites (PEI@PGD-H) as Highly Efficient CO2 Adsorbents

Searching for highly efficient and robust CO2 adsorbents is very important for CO2 capture, utilization, and storage. In this study, new polyethylenimine-grafted metal–organic framework (MOF)–polymer composites, abbreviated as PEI@PGD-H, were synthesized via high internal phase emulsion (HIPE) template polymerization of divinylbenzene and glycidyl methacrylate, followed by in situ generation of HKUST-type MOF in the presence of hydrophobic-modified CuO nanoparticles via the reaction of CuO with 1,3,5-benzenetricarboxylic acid and then polyethylenimine (PEI) functionalization via epoxy–amine reaction and amine–metal sites interaction. The coexistence of the hierarchical interconnected porous skeleton of poly(glycidyl methacrylate–divinylbenzene) (PGD), high specific surface area of MOF, and chemical CO2 adsorption of PEI endows PEI@PGD-H with high CO2 adsorption capacity, rate, and selectivity. PEI70@PGD-H shows a CO2/N2 separation factor as high as 76 and CO2 adsorption capacities of 4.3, 3.0, and 1.8 mmo...

Methane adsorption constrained by pore structure in high‐rank coals using FESEM, CO2 adsorption, and NMRC techniques

AbstractTo evaluate the impacts of nanopores of high‐rank coals on coalbed methane adsorption and storage, 12 anthracite and semianthracite coal samples from Yangquan and Shouyang blocks in the Qinshui Basin were investigated. Field emission scanning electron microscopy (FESEM) and CO2 adsorption combined with nuclear magnetic resonance cryoporometry (NMRC) experiments were used to evaluate the pore structure with diameters ranging from 0 to 500 nm and their impact on adsorption capacity based on qualitative and quantitative analysis. The results show that a coalification jump from semianthracite to anthracite occurred in the study area due to the magmatic intrusion. In the process, the volume of supermicropores and micropores largely increased while the volume of transition pores and mesopores decreased slightly. Additionally, vitrinite gets purified and enriched during the rapid maturation of coal reservoir, which is beneficial to the microporous structure development. The pore size distribution (PSD) of anthracite is mainly divided into two types, which are in serrated and decreasing forms, respectively. Higher vitrinite content can promote the formation of decreasing type (type II), which corresponds to a lower degree of complexity. The fractal dimensions indicate that the heterogeneity of coal samples is increasing with the decrease in pore size. Accordingly, the increase in pore heterogeneity corresponds to the lower adsorption capacity. The main pore sizes that contribute to CBM adsorption include two parts: 25‐30 nm and 50‐60 nm. For the supermicropores with large specific surface areas, the pore system detected by CO2 molecules is not conducive to CBM adsorption, while the increase in pore volume can improve the adsorption rate and capacity of CO2. These findings are vital for a precisely understanding of nanoscale pores as well as future CBM exploitation.

Kinetic study on CO2 adsorption behaviors of amine-modified co-firing fly ash

Abstract Coal and biomass fly ash was impregnated with tetraethylenepentamine (TEPA) to prepare solid CO2 sorbent. Experimental CO2 adsorption capacities of the sorbent in fixed-bed column were fitted to several kinetic equations. The modified Avrami fractional kinetic model could accurately predict the CO2 adsorption kinetic behaviors of the sorbent under different conditions. CO2 adsorption rate increases with the increase in temperature, initial CO2 concentration and gas flow rate, as a result of the decreased CO2 diffusion resistance. A mathematical model was proposed and demonstrated to well predict the CO2 adsorption breakthrough curves in the fixed-bed column. Effects of temperature, initial CO2 concentration and gas flow rate on the mass transfer kinetic behaviors of the desired sorbent were investigated. The positive effect of these factors on promoting the overall mass transfer coefficient and the internal mass transfer coefficient is not significant. The external mass transfer coefficient will be remarkably reinforced with the increase in these operating parameters, due to the change in viscosity and density of the gas phase and the reduced external mass transfer resistance. Internal mass transfer process is determined as the rate-limiting step for CO2 adsorption. The results will lay the groundwork for future scale-up application of the sorbent in post-combustion CO2 capture.

Piperazine‐modified activated alumina as a novel promising candidate for CO2 capture: experimental and modeling

AbstractIn this research, the CO2 adsorption process was studied using modified activated alumina with a piperazine solution as a novel sorbent. Activated alumina was modified with a piperazine solution concentration in the range of 1–4 wt%. Adsorption experiments were performed to evaluate the operating parameters, including CO2 pressure in the range of 2–8 bar, adsorbent dosage in the range of 0.5–2 g, temperature in the range of 25–85°C and adsorbent mesh in the range of 200–800 micron. Maximum adsorption capacity (222.01 mg CO2/g modified activated alumina) was determined at a temperature of 25°C, pressure of 8 bar, and adsorbent dosage of 0.5 g, with a piperazine solution of 2 wt%. The results of the experiments showed that the rate of CO2 adsorption increases with increasing pressure and decreasing temperature. The Freundlich isotherm model with correlation coefficient of 0.999 was found to be the best for fitting the CO2 adsorption isotherm data. The kinetic study also indicated that the Elovich model fits the experimental kinetic data well. The negative values of Gibbs free energy change (ΔG°) and enthalpy change (ΔH°) show that the reaction is spontaneous in nature and exothermic. The negative value of entropy change (ΔS°) shows a reduction in the irregularity of the adsorption process. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

N-doped porous carbons from low-temperature and single-step sodium amide activation of carbonized water chestnut shell with excellent CO2 capture performance

The aim of this study is to exploit low-cost N-doped porous carbonaceous adsorbents with excellent CO2 adsorption properties. Herein, the N-enriched porous carbons were obtained through a single-step sodium amide activation of carbonized water chestnut shell at 400–500 °C. The optimal sample possesses high CO2 uptake of 4.50 mmol/g (25 °C) and 6.04 mmol/g (0 °C) at atmospheric pressure. Additionally, this sample displays high CO2/N2 selectivity, stable cyclic ability, moderate CO2 isosteric heat of adsorption, fast CO2 adsorption rate, and high dynamic CO2 uptake. In addition to the two well-known factors i.e. volume of narrow micropore and N content, the pore size distribution is also found to play major role in deciding CO2 adsorption performance for these adsorbents. The features of excellent CO2 adsorption properties, low-cost raw materials, low reaction temperature and facile preparation demonstrate that these adsorbents are prospective in the application of CO2 capture.

Li-LSX-zeolite evaluation for post-combustion CO2 capture

Lithium low silica X type (Li-LSX) zeolite is typically used for industrial N2/O2 separation processes, but its potential as a carbon dioxide capture sorbent has not been fully evaluated yet. In this work, Li-LSX zeolite was investigated as CO2 sorbent under post- combustion conditions in TGA and Fixed-bed configurations. The maximum adsorption capacity and CO2/N2 selectivity were determined to be 4.43 mmol g−1 and 85.7 at 60 °C and in presence of 14% CO2, using a packed bed configuration. The CO2 and N2 adsorption capacity was decreased of 10 mol% when the initial calcination temperature was raised from 60 to 300 °C due to a decreased micropore surface. However, the high calcination temperature increased the CO2 selectivity to 128.1 and increased the adsorption rates due to enhanced basicity (1 order of magnitude) and external surface (+75 to 80%) in the Li-LSX zeolite.The sorption stability at 60 °C was found to be excellent during 85 sorption cycles over 35 h period with Li-LSX showing negligible difference in adsorption capacity throughout the cycles and a working capacity of 2.45 mmolCO2/g after an initial calcination at 550 °C (2 min) and cyclic adsorption at 60 °C (6 min) and desorption at 420 °C (5 min). The Avrami kinetic model shows the coexistence of different adsorption mechanisms. CO2 adsorption rate increased with the increasing CO2 partial pressure, as a result of the facilitated CO2 diffusion processes. Film diffusion was determined as the rate-limiting step for CO2 adsorption. Therefore, based on these findings, Li-LSX represents a promising sorbent for post-combustion carbon capture.

Methanol oxidation reaction on Pt based electrocatalysts modified ultramicroelectrode (UME): Novel electrochemical method for monitoring rate of CO adsorption

Novel fast scan cyclic voltammetry (FSCV) based method has been developed to study methanol oxidation reaction on Pt nanoparticles (PtNPs) based catalysts. To support the cyclic voltammetry measurements at higher scan rates, micron-sized electrode geometries viz. PtNPs loaded on the single strand of carbon fiber (SSCF) and PtNPs decorated multiwalled carbon nanotubes (MWCNTs), loaded on commercial ultramicroelectrode (UME) have been employed. Deconvolution of the voltammograms obtained during methanol oxidation revealed three major anodic peaks. These peaks have been plausibly attributed to the electron transfer processes viz. methanol oxidation into CO/other intermediates, oxidation of these intermediates into CO2 and adsorption of un-oxidized CO on the catalyst surface. The peaks due to CO adsorption have been elucidated as a function of scan rates. The area under the peak as a function of time has been correlated to the rate of CO adsorption on these catalysts. The average rate of CO adsorption in methanol oxidation at Pt-SSCF and Pt-MWCNTs/UME are estimated to be 1.08 × 10−8 mol cm−2 s−1 and 13.5 × 10−8 mol cm−2 s−1 respectively. This novel method is proposed to generalize to any electrocatalysts of interest.

Relationships between the Charge-Discharge Methods and the Gas Adsorption Performance of a Supercapacitive Swing Adsorption Module for CO2 Separation

Introduction: Supercapacitive swing adsorption (SSA) is a gas separation technology that is based on selective adsorption and desorption of a gas from a gas mixture upon capacitive charging and discharging activated carbon electrodes.1,2 SSA is a promising technology due to its facile reversibility, significant sorption capacity, complete gas selectivity, and energy efficiency. In this study, we simplified the cell design and enlarged the electrode area of SSA modules. These new cell features are expected to increase the scalability of SSA technology. We defined metrics that allow for a quantitative evaluation of the energetic and adsorption performance of SSA cycles. Using these metrics, we quantitatively determined the influence of different electrical charge-discharge methods on the energetic and CO2 adsorption performance, and identified the most favorable charge-discharge method. Methods: The cross-sectional view of a SSA module is shown in Figure a. The SSA module was operated in gas flow-through mode and fed by a moistened 15% : 85% CO2 : N2 gas mixture serving as a flue gas simulant. In the SSA module, the gas was distributed by radial gas flow system, in which gas flowed from the inlet port in the center to the outlet port in the periphery of the SSA module. This design eliminated the use of gas flow channels, and simplified SSA module configuration. The electrode area was 49 cm2, which was 25 times of that in our previous study2. The CO2 concentration of SSA effluent gas was analyzed and recorded. The electrochemical behavior of the SSA module was controlled and measured using a potentiostat in a two-electrode configuration. Four different charge-discharge methods at voltages between 0 and -1 V were used to evaluate SSA performance, namely GCD (galvanostatic charging-discharging, Figure b), GCD+Pstat (GCD with potentiostatic holding steps between each GCD step, Figure c), GCD+OC (GCD with open-circuit holding steps between each GCD step, Figure d), and Combined (galvanostatic charging followed by holding step at open circuit, and galvanostatic discharging followed by potentiostatic holding step at 0 V, Figure e). Results: We introduced energetic and adsorption metrics to quantitatively evaluate SSA performance for CO2 adsorption. These metrics are specific capacitance, Coulomb efficiency, energy efficiency, energy loss, sorption capacity, electron efficiency, energy consumption, adsorption rate, and time-energy efficiency. Using these metrics, we determined how different charging methods affect the energetic and adsorption performance of SSA module. The galvanostatic charge-discharge method was most time-energy efficient due to its shortest charge time and lowest energy loss. The highest time-energy efficient for CO2 adsorption (7.5 µmol.kJ-1.s-1) was obtained with the galvanostatic charge-discharge methods at 50 mA. Increasing the constant charging current improved the energetic performance but decreased CO2 adsorption capacity. The introduction of holding steps favored CO2 adsorption at the cost of higher energy loss. A holding step of 30 min duration was sufficient for the full completion of CO2 adsorption and desorption. The highest CO2 adsorption capacity (87.5 mmol.kg-1), highest electron efficiency (0.2 molecule.electron-1), lowest energy consumption (109 kJ.mol-1) and highest CO2 adsorption rate (34 µmol.kg-1.s-1) were obtained by Combined method with 30 min holding steps. Conclusions: We demonstrated a simplified SSA module with enlarged electrode area, which is expected to benefit the scale-up of SSA technology for CO2 adsorption and separation. Our results provide systematic method to evaluate SSA performance and improve the understanding of the relationships between energetic properties and gas adsorption performance of SSA. This findings is critical to understanding the mechanism of SSA phenomena and to exploring SSA application. References 1 B. Kokoszka, N. K. Jarrah, C. Liu, D. T. Moore and K. Landskron, Angew. Chemie - Int. Ed., 2014, 53, 3698–3701. 2 C. Liu and K. Landskron, Chem. Commun., 2017, 53, 3661–3664. Figure 1

Promoted adsorption of CO2 on amine‐impregnated adsorbents by functionalized ionic liquids

Amine‐impregnated adsorbents are promising alternatives to aqueous amines for CO2 capture. However, the diffusion‐controlled CO2 adsorption process is a significant issue associated with them, resulting in the insufficient utilization of amine groups. Herein, we propose the use of functionalized ionic liquids 1‐ethyl‐3‐methylimidazolium acetate ([emim][Ac]) with chemical reactivity to CO2 and low viscosity as the additive to amine‐impregnated adsorbents. The key is that [emim][Ac] does not show drastic increase in viscosity after reacting with CO2. Taking the polyethyleneimine (PEI)‐impregnated SBA‐15 as a model system, it is found that the CO2 capacities of PEI/SBA‐15 composites are improved by 86%, and the active site efficiencies are improved by 270%, after the addition of [emim][Ac]. The addition of [emim][Ac] to PEI/SBA‐15 composites also helps improve the CO2 adsorption rate and recycling stability of composites. Therefore, [emim][Ac] offers the opportunity to fabricate amine‐impregnated adsorbents with simultaneously improved CO2 capacities, adsorption kinetics, and recycling stability. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3671–3680, 2018

Supported ionic liquid sorbents for CO2 capture from simulated flue-gas

Abstract Supported ionic liquid (IL) sorbents for CO2 capture were prepared by impregnating tetramethylammonium glycinate ([N1111][Gly]) into four types of porous materials in this study. The CO2 adsorption behavior was investigated in a thermogravimetric analyzer (TGA). Among them, poly(methyl methacrylate) (PMMA)-[N1111][Gly] exhibits the best CO2 adsorption properties in terms of adsorption capacity and rate. The CO2 adsorption capacity reaches up to 2.14 mmol·g− 1 sorbent at 35 °C. The fast CO2 adsorption rate of PMMA-[N1111][Gly] allows 60 min of adsorption equilibrium time at 35 °C and much shorter time of 4 min is achieved at 75 °C. Further, Avrami's fractional-order kinetic model was used and fitted well with the experiment data, which shows good consistency between experimental results and theoretical model. In addition, PMMA-[N1111][Gly] remained excellent durability in the continuous adsorption–desorption cycling test. Therefore, this stable PMMA-[N1111][Gly] sorbent has great potential to be used for fast CO2 adsorption from flue-gas.

Characterization of commercial off-the shelf regenerable sorbent to scrub carbon dioxide in a portable life support system

A resin bead Mitsubishi DIAION™ CR20 was identified and characterized as a first commercial off-the shelf regenerable carbon dioxide (CO2) sorbent candidate for space life support system applications at room temperature. The CO2 adsorption rates and capacities of CR20 at varying CO2 partial pressures were obtained. The data were used to numerically simulate CO2 adsorption by a swingbed, a pair of two sorbent beds that alternately adsorb and desorb CO2 in a space suit portable life support system (PLSS). The result demonstrated that a reasonable volume of CR20 would be able to continuously adsorb CO2 with bed-swing interval of 4 min at 300-W metabolic rate, and that commercial off-the shelf CR20 would have similar performance of CO2 adsorption to the proprietary swingbed sorbent SA9T for PLSS applications.

Quaternized Chitosan/PVA Aerogels for Reversible CO2 Capture from Ambient Air

Developing inexpensive and highly efficient CO2 air capture technologies is an important solution for solving the greenhouse problem. In this work, we used the low-cost quaternized chitosan (QCS)/poly(vinyl alcohol) (PVA) hybrid aerogels with quaternary ammonium groups and hydroxide ions to reversibly capture CO2 from ambient air by humidity swing. The CO2 capture capacity and adsorption rate of the aerogels were investigated over the temperature range 10–30 °C. The CO2 capture capacity of the aerogels was measured to be about 0.18 mmol/g, which is 38% higher than the state-of-the-art commercial membrane. In addition, we proposed a modified pseudo-first-order kinetic model considering both the CO2 adsorption and the H2O desorption, which describes the experimental results very well. For the first time, the moisture-swing CO2 adsorbent is built by low-cost biomass material, which opens up a new approach for the design of the moisture-swing CO2 adsorbent.

Ultra-microporous adsorbents prepared from vine shoots-derived biochar with high CO2 uptake and CO2/N2 selectivity

There is a growing interest in developing renewable biomass-based adsorbents to be used in numerous applications, including CO2 capture in postcombustion conditions. In the present study, several activated carbons (ACs) were produced from vine shoots-derived biochar through both physical and chemical activation using CO2 and KOH, respectively. The performance of these ACs was tested in terms of CO2 uptake capacity at an absolute pressure of 15 kPa and at different temperatures (0, 25, and 75 °C), apparent selectivity towards CO2 over N2, and isosteric heat of adsorption. At 25 °C, the chemically ACs with KOH impregnation exhibited the highest CO2 adsorption capacity, which was similar or even higher than those recently reported for a number of carbon-based adsorbents. However, the AC prepared through physical activation with CO2 at 800 °C and a soaking time of 1 h appears as the most promising adsorbent analyzed here, due to its higher CO2 uptake capacity and adsorption rate at relatively high temperature (75 °C), its relatively high selectivity at this temperature, and its apparently low energy demand for regeneration. Given that physical activation with CO2 is more feasible at industrial scale than chemical activation using corrosive alkalis, the results reported here are encouraging for further development of vine shoots-derived adsorbents.

Molecular Layer Deposition-Modified 5A Zeolite for Highly Efficient CO2 Capture.

Effective pore mouth size of 5A zeolite was engineered by depositing an ultrathin layer of microporous TiO2 on its external surface and appropriate pore misalignment at the interface. As a result, a slightly bigger N2 molecule (kinetic diameter: 0.364 nm) was effectively excluded, whereas CO2 (kinetic diameter: 0.33 nm) adsorption was only influenced slightly. The prepared composite zeolite sorbents showed an ideal CO2/N2 adsorption selectivity as high as ∼70, a 4-fold increase over uncoated zeolite sorbents, while maintaining a high CO2 adsorption capacity (1.62 mmol/g at 0.5 bar and 25 °C) and a fast CO2 adsorption rate.

Template-directed fabrication of MIL-101(Cr)/mesoporous silica composite: Layer-packed structure and enhanced performance for CO2 capture

A novel hybrid material constituted of MIL-101(Cr) and mesoporous silica was successfully assembled through an in-situ hydrothermal method. The MCM−41 with well-ordered mesopores acted as the structure-directing agent, which regulated the growth of MIL-101(Cr) crystals along a certain direction and restricted the expansion of framework. Meanwhile, the hydroxyl groups existed in MCM−41 preferentially coordinated with the Cr3+ centers in MOF, followed by the layer-packed arrangement of MIL-101(Cr) nanocrystals on the surface of matrix. The structural characterizations further revealed that the introduction of MCM−41 could increase the micropore volume and specific surface area. The MIL-101(Cr)@MCM−41 exhibited higher CO2 uptake capacity and adsorption rate compared with the original MIL-101(Cr) at 298 K and 1 bar. Via ideal adsorbed solution theory (IAST), it could be further predicted that the composite was more inclined to adsorb CO2 than N2. The calculated isosteric heats of CO2 adsorption and desorption activation energy demonstrated that the interaction between CO2 molecules and the composite was also enhanced. The as-prepared MIL-101(Cr)@MCM−41 showed good reusability and could be easily regenerated without any reduction in its CO2 adsorption capacity. Hence, this study opened up a new pathway for designing hierarchical porous structured MOF-based materials with advanced gas separation performance.

A novel and green CO2 adsorbent developed with high adsorption properties in a coal mine refuge chamber

A novel and modified soda lime with higher adsorption rate and capacity was developed. According to the multi-index orthogonal experiments, the best combinations of soda lime with different mass fractions is CMSS 8.5%, H2O 10.5% and NaOH 8.5% and the order of influence on CO2 adsorption rate of different compositions (mass fraction) is NaOH > H2O > CMSS. The modified soda lime was characterized by using various techniques for their pore structure and surface area. The porosity of optimal soda lime is 27.13%, total pore volume 0.19 mL/g and total surface area 6.10 m2/g. The Langmuir isotherm model fitted best among the three isotherm models, indicating the maximum adsorption takes up at 25 °C. The CO2 adsorption kinetic study was performed by using two kinetic models, and the second order was found fitted best with the experimental data with maximum error% of 2.28%. The adsorption rate still remains at a high level in an environment with high temperature and high humidity (humidity 70% and temperature 30 °C). Moreover, technical parameters appropriate for engineering applications were analyzed and calculated. It can be concluded that the novel adsorbent has several advantages, such as its being lower in cost, higher in efficiency, more stable in nature, higher in strength, few in secondary pollution and lower in dust outflow. It was demonstrated that the adsorption capacity increased by 36.2% and the adsorption rate increased by 39.5%.

Unraveling the Mechanism for the Sharp‐Tip Enhanced Electrocatalytic Carbon Dioxide Reduction: The Kinetics Decide

AbstractThe electrocatalytic reduction reaction of carbon dioxide can be significantly enhanced by the use of a sharp‐tip electrode. However, the experimentally observed rate enhancement is many orders of magnitudes smaller than what would be expected from an energetic point of view. The kinetics of this tip‐enhanced reaction are shown to play a decisive role, and a novel reaction‐diffusion kinetic model is proposed. The experimentally observed sharp‐tip enhanced reaction and the maximal producing rate of carbon monoxide under different electrode potentials are well‐reproduced. Moreover, the optimal performance shows a strong dependence on the interaction between CO2 and the local electric field, on the adsorption rate of CO2, but not on the reaction barrier. Two new strategies to further enhance the reaction rate have also been proposed. The findings highlight the importance of kinetics in modeling electrocatalytic reactions.

Unraveling the Mechanism for the Sharp-Tip Enhanced Electrocatalytic Carbon Dioxide Reduction: The Kinetics Decide.

The electrocatalytic reduction reaction of carbon dioxide can be significantly enhanced by the use of a sharp-tip electrode. However, the experimentally observed rate enhancement is many orders of magnitudes smaller than what would be expected from an energetic point of view. The kinetics of this tip-enhanced reaction are shown to play a decisive role, and a novel reaction-diffusion kinetic model is proposed. The experimentally observed sharp-tip enhanced reaction and the maximal producing rate of carbon monoxide under different electrode potentials are well-reproduced. Moreover, the optimal performance shows a strong dependence on the interaction between CO2 and the local electric field, on the adsorption rate of CO2 , but not on the reaction barrier. Two new strategies to further enhance the reaction rate have also been proposed. The findings highlight the importance of kinetics in modeling electrocatalytic reactions.

Design of ZIF-8/ion copolymer hierarchically porous material: Coordination effect on the adsorption and diffusion for carbon dioxide

The novel CO2 adsorbent (ZPMAC) was constructed by a facile in-situ growth of ZIF-8 onto the surface of a mesoporous amino-functionalized ion copolymer (PMAC). The existence of coordination effect between Zn2+ from ZIF-8 and nitrogen atom from the amino-alkyl chain in PMAC changed the pore structure of substrate for enhancing the amount of CO2 capture and accelerated the rate of CO2 adsorption. The ion copolymer PMAC, pristine ZIF-8 and hierarchically porous hybrid material ZPMAC were characterized by SEM, TEM, TGA, N2 adsorption-desorption, FT-IR, XRD, UV, and XPS techniques. It was observed that ZIF-8 loaded on the surface of PMAC uniformly and tightly. In the growth process of ZIF-8 nanoparticles, zinc ions were firstly coordinated with nitrogen atoms of the amino-alkyl chain in PMAC sample, and subsequently reacted with 2-methylimizadole to generate ZIF-8 nanoparticles. Obviously, the surface areas of ZPMAC increased and smaller peak value of micropore distribution was generated by the strong coordination interaction between ZIF-8 and PMAC after ZIF-8 modified. Meanwhile, the appearance of hierarchically porous structure was conducive to the transportation and adsorption of CO2 molecules, thus enhancing the amount of CO2 capture and the rate of adsorption effectively. This study was intended to design a new kind of hybrid materials by the means of in-situ growth of MOF materials onto the IL-type polymers and further study the influences of the structure and properties of ionic-type hybrid materials on the absorption capacity to meet the requirements of various applications.