High CO2 Uptake Capacity Research Articles

The Zr-Doped CaO CO2 Sorbent Fabricated by Wet High-Energy Milling

We fabricated the Zr-doped CaO sorbent for high-temperature CO2 capture by the wet high-energy co-milling of calcium carbonate and natural zirconium dioxide (baddeleyite) for the first time. The morphology of the material was examined by scanning electron microscopy, energy-dispersive X-ray analysis and X-ray diffraction. Its CO2 uptake capacity was determined using thermogravimetric analysis. After 50 carbonation–calcination cycles, the Zr-doped CaO sorbent characterized by a high enough CO2 uptake capacity of 8.6 mmol/g and unchanged microstructure due to CaZrO3 nanoparticles uniformly distributed in the CaO matrix to prevent CaCO3 sintering under carbonation. The proposed easy-to-implement CaO-based sorbents fabrication technique is promising for industrial application.

One-pot synthesis of digestate-derived biochar for carbon dioxide capture

Digestate from Anaerobic Digestion (AD) is a very common waste produced by European biogas plants and its current method of reuse is as a fertilizer or as soil amendment. This in turn however gives rise to some other environmental concerns which include greenhouse gas emissions and volatilization of ammonia causing ammonia pollution. Biochar is an environmentally friendly and low-cost product for CO2 capture and sequestration. Thus, we have provided one simple method to convert AD digestate into biochar-based sorbents of CO2. In addition, the nitrogen-functionalised porous carbon has been reported to be effective in improving the uptake of CO2. However, most of them were prepared using multiple steps. In this work, N-doped biochar was prepared by a one-step method of modifying AD digestate by urea. The results show that the addition of N can increase CO2 uptake significantly. Thus, the adsorbent modified by urea with a ratio of 1:1 results in the highest CO2 uptake capacity (1.22 mmol g−1), indicating digestate’s potential application for carbon capture and storage.

Mechanochemical synthesis of three-component graphene oxide/ordered mesoporous carbon/metal-organic framework composites

Graphene oxide-containing ordered mesoporous carbon (OMC/GO) composites were synthesized by mechanochemical soft-templating of mimosa tannin and graphene oxide with triblock copolymer Pluronic F127. Graphene oxide was added to modify the surface properties of ordered mesoporous carbon. Next, copper containing MOF (CuBTC) was synthesized in the presence of the OMC/GO composite via dry milling to obtain a three-component composites with different compositions. The composite with 50 wt% of CuBTC exhibited high CO2 uptake capacity of 5.39 mmol·g−1 at 0 °C and 1 bar. This study showed that CuBTC was initially crystallized in mesopores of carbonaceous materials, and next on their external surface. Small OMC amounts (~1 and ~3 wt%) added during the mechanochemical synthesis of CuBTC resulted in the enhanced surface area of the obtained two-component composites reaching 1930 m2·g−1 as compared to those of parent materials. This paper reports a comprehensive study of carbon-CuBTC composites over a wide range of compositions, which may be interesting from the viewpoint of advancing and understanding the mechanochemical synthesis of composite materials with high surface areas, enhanced porosity and interfacial properties.

Novel Insights into Activated Carbon Derived from Municipal Solid Waste for CO2 Uptake: Synthesis, Adsorption Isotherms and Scale-up

Abstract Recently, developing bio-based carbon materials due to the surface chemistry and a large spectrum of pore structures have received much attention. In the present work, a series of activated carbon (AC) adsorbents were synthesized from the compost derived by the mechanical/biological treatment of municipal solid wastes and evaluated regarding their CO2 uptake. The AC samples were characterized by sulfuric acid and calcination by N2 at 400 and 800 °C. Then, the CO2 uptake capacities were evaluated by dynamic breakthrough experiments in a temperature range of 40-100 °C and pressures up to 3 bar. The presented data were properly described by Langmuir model and it was revealed that the CMSW-S-800 sample, treated with sulfuric acid and activated at 800 °C, has the highest CO2 uptake capacity with an amount adsorbed around 2.6 mol/kg at 40 °C. In the next step, a mathematical model has been developed to match the experimental dynamic breakthrough data and design a pressure swing adsorption (PSA) cyclic process to evaluate the capacity and potential of the best AC sample for CO2 adsorption. The results arising from this work showed a possible route for the application of the compost as a source of activated carbon for the sorption of greenhouse gases.

Synthesis of functionalized 3D microporous carbon foams for selective CO2 capture

Porous carbon materials have been considered as the promising media for post combustion CO2 capture. Development and design of cost-effective carbons with high adsorption capacity and selectivity of CO2 over other gases at low CO2 partial pressures has attracted increasing attention. In this study, a category of functionalized 3D microporous carbon foam was prepared by using inexpensive and commercially available polyisocyanurate foam (PIR) as the precursor via a facile one-step chemical activation process. The porous structure and surface chemistry of the carbon foams can be tailored by adjusting the activation temperature and KOH/PIR mass ratio. At 25 ℃ and a CO2 partial pressure of 0.15 bar, the carbon foam of FC7001 with highest volume of fine micropores (<0.44 nm) and desirable surface chemistry exhibited exceptionally high CO2 uptake of 2.3 mmol/g whereas FC6001, which had a pure single pore size centered at 0.37 nm, showed highest Henry’s law CO2/N2 selectivity of 200. Furthermore, high CO2 uptake capacity of 19 mmol/g at CO2 pressure of 20 bar and ambient temperature was obtained for the carbon foam prepared at a higher activation temperature and KOH/precursor ratio and with a high surface area of 2207 m2/g and micropore volume of 0.876 cm3/g. Advanced characterization confirmed that the unique ultra-microporous structure and surface chemistry originated from intercalated potassium in the form of surface extra-framework ions governed the selective CO2 adsorption of the carbon foams at low CO2 partial pressures whilst the high micropore volume determined the CO2 adsorption at high CO2 pressure. This work provides a potentially new pathway to recycle polyisocyanurate foams by producing efficient CO2 adsorbents.

Ethylenediamine loading into a manganese-based metal-organic framework enhances water stability and carbon dioxide uptake of the framework.

Metal–organic frameworks (MOFs) based on 2,5-dihydroxyterepthalic acid (DOBDC) as the linker show very high CO2 uptake capacities at low to moderate CO2 pressures; however, these MOFs often require expensive solvent for synthesis and are difficult to regenerate. We have synthesized a Mn-DOBDC MOF and modified it to introduce amine groups into the structure by functionalizing its metal coordination sites with ethylenediamine (EDA). Repeat framework synthesis was then also successfully performed using recycled dimethylformamide (DMF) solvent. Characterization by elemental analysis, FTIR and thermogravimetric studies suggest that EDA molecules are successfully substituting the original metal-bound DMF. This modification not only enhances the material's carbon dioxide sorption capacity, increasing stability to repeated CO2 sorption cycles, but also improves the framework's stability to moisture. Moreover, this is one of the first amine-modified MOFs that can demonstrably be synthesized using recycled solvent, potentially reducing the future costs of production at larger scales.

Tuning Na2ZrO3 for fast and stable CO2 adsorption by solid state synthesis

This work assessed the possibility to tune the CO2 capture performance of Na2ZrO3 with respect to CO2 uptake and CO2 sorption rate by varying the conditions used in the solid-state synthesis. The resulting Na2ZrO3 were characterized by XRD, SEM-EDS, XPS and TGA. A structural, chemical, microstructural and kinetic analysis of the Na2ZrO3–CO2 system over one cycle was performed to identify the correlation with the sorbent performance. The heating rate, the molar ratio of the Na2CO3 and ZrO2 used in the synthesis of Na2ZrO3, as well as additional powder processing steps of the reactants, all had a major impact on the sorbent’s CO2 capture performance. The best performing sorbent with the highest CO2 uptake capacity (4.83 mmol CO2/g) and absorption rate (30. 5 nmmol/s) at 700 °C was obtained when the Na2CO3 and ZrO2 reactants were processed by ball milling varying the molar ratio of 1:1 and a synthesis heating rate of 1 °C/min. Under these conditions, the optimised Na2ZrO3 exhibited 86.5% conversion in 10 min with respect to the theoretical value. Na2ZrO3 synthesised using the optimised conditions as listed above were constructed with nanocrystals of ~ 20 nm in average diameter as observed using XRD (Sherrer’s formula). The Na2ZrO3 synthesised in this study favoured the ionic solid-state diffusion of Na and O from the core to the surface of the material to readily react with CO2. Moreover, an excellent cyclic stability of the sorbent over 70 sorption/desorption cycles was noted after an initial decay when the CO2 cycles were shortened to 5 min.

Insights and utility of cycling-induced thermal deformation of calcium-based microporous material as post-combustion CO2 sorbents

On the quest of finding ideal sorbent for post-combustion CO2 capture, calcium-based sorbent seems to have the potential, but often it cannot sustain its reactivity, especially after repeated cycle of sorption. This work aims to unravel the controlling factors in carbonation reaction and thermal-induced deformation of skeleton pore network that limits the CO2 absorptivity of calcium-based sorbent. Through precise measurement of CO2 absorption activity using TGA/DSC and a series of characterization, this study paves the way for the development of next-generation CaO sorbent that has high CO2 uptake capacity and thermal stability. Key findings include CaO particles with severe point defects contribute to fast CO2 absorption activity. The transformation from CaCO3 phase to CaO phase from organic precursor is 4 times higher than the inorganic precursor. Decomposition of calcium formate is thermally stable regardless of calcination temperature. Citrate-based structure precursor is able to produce homogeneous nanosized CaO particle. Shifting of reaction controlling regime from fast carbonation reaction to diffusion limited stage happened at Thiele modulus of 1.35. Lastly, first stage of fast carbonation reaction will take place at CaO sorbent’s surface with proximate zero activation energy and second stage of slow carbonation reaction is controlled by high activation energy of ion diffusion behavior in CaCO3 ionic crystals at product diffusion layer. Future research direction can focus on reproducing long periodical citrate-like structural precursor using sol-gel method to mimic the behavior of calcium formate and calcium citrate to form nano-sized CaO particles with thermally stable crystal structure.

Adsorptive removal of CO2 on Nitrogen-doped porous carbon derived from polyaniline: Effect of chemical activation

Nitrogen-doped porous carbons (NDCs) with high surface areas were prepared using a nitrogen containing polymer (polyaniline) as precursor with H3PO4, ZnCl2 and KOH activation. The effects of activation conditions on the structure of adsorbents and CO2 adsorption were also investigated. The porous structure and surface chemical composition of microporous carbon were analyzed and characterized by N2 adsorption-desorption, elemental analysis (CHNS), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The effect of temperature on CO2 adsorption was studied at 298, 308 and 318 K on the prepared adsorbents activated by H3PO4, KOH and ZnCl2. Among activating agents studied, H3PO4 was the best activator for the structure development whereas the N-doped porous carbon obtained by ZnCl2 had high CO2 adsorption capacity of 3.54 mmol/g at ambient temperature and pressure with CO2 heat of adsorption energy of 55 kJ/mol at lower surface coverage. The selectivity of CO2 over N2 by H-2,650, Zn-2,500 and K-1,650 (CO2: N2 = 015:0.85, 298 K, 1 bar), predicted by the ideal adsorbed solution theory (IAST) model, were attained 13.65, 26.32 and 6.41, respectively. The multi advantages of these sorbents such as low cost, easy synthesis, lower heat of adsorption, high CO2 uptake capacity and high CO2/N2 selectivity prove the suitability of nitrogen-doped carbons for CO2 capture.

Selective Carbon Dioxide Capture in Antifouling Indole-based Microporous Organic Polymers

Intermolecular synergistic adsorption of indole and carbonyl groups induced by intermolecular hydrogen bonding makes microporous organic polymer (PTICBL) exhibit high CO2 uptake capacity (5.3 mmol·g−1 at 273 K) and selectivities (CO2/CH4 = 53, CO2/N2 = 107 at 273 K). In addition, we find that indole units in the PTICBL networks inhibit the attachment of bacteria (E. coil and S. aureus) on the surface of PTICBL and extend its service life in CO2 capture.

Ionic Liquids: Potential Materials for Carbon Dioxide Capture and Utilization

The nonvolatility, structure-tunability and high CO2 uptake capacity render ionic liquids (ILs) the most exciting materials for the carbon dioxide (CO2) capture and fixation to value-added chemical ...

Hollow Microspherical and Microtubular [3 + 3] Carbazole-Based Covalent Organic Frameworks and Their Gas and Energy Storage Applications.

Covalent organic frameworks (COFs) are a family of crystalline porous networks having applications in various fields, including gas and energy storage. Despite respectable progress in the synthesis of such crystalline materials, examples of the use of template-free methods to construct COFs having hollow nano- and microstructures are rare. Furthermore, all reported methods for synthesizing these hollow structural COFs have involved [4 + 2] and [3 + 2] condensations. Herein, we report the synthesis of hollow microspherical and microtubular carbazole-based COFs through template-free, one-pot, [3 + 3] condensations of the novel triamine 9-(4-aminophenyl)-carbazole-3,6-diamine (Car-3NH2) and triformyl linkers with various degrees of planarity. Depending upon the monomer's planarity, a unique morphological variety was observed. A time-dependent study revealed that each COF formed through an individual mechanism depended on the degree of planarity of the triformyl linker; it also confirmed that the hollow structures of these COFs formed through inside-out Ostwald ripening. Our COFs exhibited high Brunauer-Emmett-Teller surface areas (up to ca. 1400 m2 g-1), excellent crystallinity, and high thermal stability. Moreover, the CO2 uptake capacities of these COFs were excellent: up to 61 and 123 mg g-1 at 298 and 273 K, respectively. The high surface areas facilitated greater numbers of strong interactions with CO2 molecules, leading to high CO2 uptake capacities. Moreover, the prepared COFs exhibited redox activity because of their redox-active triphenylamine and pyridine groups, which can be utilized in electrochemical energy storages. Accordingly, such hollow COFs having high surface areas appear to be useful materials for industrial and biological applications.

A zinc(ii) metal–organic framework with high affinity for CO2 based on triazole and tetrazolyl benzene carboxylic acid

A new metal–organic framework {[Zn2(Htzba)2(dmtrz)]·(CH3)2NH}n (1) has already been solvothermally synthesized that exhibits a high CO2 uptake capacity.

Covalent organic frameworks (COFs) functionalized mixed matrix membrane for effective CO2/N2 separation

Covalent organic frameworks (COFs) membrane shows great potential for applications in gas storage and separation. In this work, the COF-5 nanosheet was synthesized via a facilely sonochemical method, which shows the high CO2 uptake capacities because of its unique structure. Then, COF-5 was dispersed in Pebax-1657 matrix to fabricate the mixed matrix membranes (MMMs), the resulting MMMs exhibits an enhanced CO2 permeability. Remarkably, the MMM that consists of 0.4 wt% COF-5 filler shows the highest CO2 permeability (∼493 Barrer). Furthermore, compared with the pristine Pebax-1657 membrane, the MMMs with COF-5 could impove the CO2/N2 selectivity (from 31.3 to 49.3), which almost surpassing the Robeson bond (2008). It is worth mentioning that the MMMs have stable operating performance during 120 h.

Polyamine-appended porous organic polymers for efficient post-combustion CO2 capture

Carbon capture and sequestration (CCS) has been proposed to reduce CO2 emissions from large stationary sites such as coal-fired power plants. Currently, however, implementing CCS in power plants is not economically feasible due to the high expense of removing CO2 from flue gas. There is therefore an urgent need for cost-effective CO2 capture technologies, such as efficient solid adsorbents. In this study, we develop a facile strategy that converts a cost-effective porous organic polymer (denoted as PP), which is synthesized by Friedel-Crafts alkylation reaction of dichloro-p-xylene, into outstanding CO2 adsorbents through one-step post-synthesis functionalization with polyamines. Among the adsorbents synthesized, PP-2-DETA and PP-2-TEPA show superior high CO2 uptake capacities, excellent CO2 selectivity over N2, and appropriate Qst. Furthermore, the adsorbents show good CO2 uptake capacity and excellent stability toward both water vapor and regeneration cycles under dynamic flow conditions. Significantly, our samples exhibite much faster adsorption-desorption kinetics than mmen-Mg2(dobpdc) and MCM-41-NH2, which are two outstanding amine-functionalized adsorbents.

High efficiency synthesis of HKUST-1 under mild conditions with high BET surface area and CO2 uptake capacity

This study focuses on the development of a hydrothermal method for the rapid synthesis of good quality copper benzene-1,3,5-tricarboxylate (referred to as HKUST-1) with high yield under mild preparation conditions to address the issues associated with reported methods. Different synthesis conditions and activation methods were studied to understand their influence on the properties of HKUST-1. It was found that mixing the precursors at 50 °C for 3 h followed by activation via methanol refluxing led to the formation of a product with the highest BET specific surface area of 1615 m2/g and a high yield of 84.1%. The XRD and SEM data illustrated that the product was highly crystalline. The sample was also tested on its capacity in CO2 adsorption. The results showed strong correlation between surface area of the sample and its CO2 uptake at 1 bar and 27 °C. The HKUST-1 prepared in this study demonstrated a high CO2 uptake capacity of 4.2 mmol/g. It is therefore concluded that this novel and efficient method can be used in the rapid preparation of HKUST-1 with high surface area and CO2 uptake capacity.

A porous Zn-based metal-organic framework with an expanded tricarboxylic acid ligand for effective CO2 capture and CO2/CH4 separation

A trigonal nanosized carboxylate ligand, 4, 4′,4″-(triazine-2,4,6-triyl-tris(benzene-4,1-diyl))tribenzoic acid (H3TAPB), has been applied in the construction of a highly porous metal−organic framework (MOF). A solvothermal reaction of H3TAPB and a zinc salt in a mixed solvent of DEF/dioxane/H2O produces the targeted porous MOF [Zn3(TAPB)2(H2O)2](DEF)4(H2O)3 (1, DEF = N,N-Diethylformamide). This MOF contains a linear Zn3 secondary building unit with two terminal water molecules occupied the axis positions, which is connected by the TAPB3− ligands to afford a 3-fold interpenetrated framework with a large calculated void volume (69.7%). The activated MOF shows exceptional porosities and high CO2 uptake capacities as well as good sorption selectivity of CO2/CH4 around room temperature.

Optimized synthesis of nano-scale high quality HKUST-1 under mild conditions and its application in CO2 capture

This study was focused on the development of an optimized method for the rapid synthesis of nano-scale HKUST-1 with high yield, high surface area and high CO2 uptake capacity but under mild conditions. A series of HKUST-1 were synthesized under different conditions, such as preparation time, temperature, activation method, etc. It was found that the nano-scale HKUST-1 MOFs (T85-3-Pm4-120) was successfully synthesized at a high yield (87%) under low temperature (85 °C) using a mixture of Triethylamine (TEA), Cu2+ and trimesic acid (TMA) with a molar ratio of 6:3:2. The highest porosity was achieved via this pristine HKUST-1 being activated (powder activation, drying at 120 °C) four times using methanol to remove impurities trapped in the pores. The best HKUST-1 MOFs (T85-3-Pm4-120) hereby prepared was then tested in CO2 adsorption and exhibited an adsorption capacity of 2.5 mmol/g. It is therefore demonstrated that the new approach proposed in this study is a rapid and effective way to synthesize highly porous HKUST-1 MOFs under mild conditions, which is of comparable surface area and CO2 uptake capacity with those MOFs prepared under harsh conditions.

Direct Synthesis of a Covalent Triazine‐Based Framework from Aromatic Amides

There have been extensive efforts to synthesize crystalline covalent triazine-based frameworks (CTFs) for practical applications and to realize their potential. The phosphorus pentoxide (P2 O5 )-catalyzed direct condensation of aromatic amide instead of aromatic nitrile to form triazine rings. P2 O5 -catalyzed condensation was applied on terephthalamide to construct a covalent triazine-based framework (pCTF-1). This approach yielded highly crystalline pCTF-1 with high specific surface area (2034.1 m2 g-1 ). At low pressure, the pCTF-1 showed high CO2 (21.9 wt % at 273 K) and H2 (1.75 wt % at 77 K) uptake capacities. The direct formation of a triazine-based COF was also confirmed by model reactions, with the P2 O5 -catalyzed condensation reaction of both benzamide and benzonitrile to form 1,3,5-triphenyl-2,4,6-triazine in high yield.

Direct Synthesis of a Covalent Triazine‐Based Framework from Aromatic Amides

AbstractThere have been extensive efforts to synthesize crystalline covalent triazine‐based frameworks (CTFs) for practical applications and to realize their potential. The phosphorus pentoxide (P2O5)‐catalyzed direct condensation of aromatic amide instead of aromatic nitrile to form triazine rings. P2O5‐catalyzed condensation was applied on terephthalamide to construct a covalent triazine‐based framework (pCTF‐1). This approach yielded highly crystalline pCTF‐1 with high specific surface area (2034.1 m2 g−1). At low pressure, the pCTF‐1 showed high CO2 (21.9 wt % at 273 K) and H2 (1.75 wt % at 77 K) uptake capacities. The direct formation of a triazine‐based COF was also confirmed by model reactions, with the P2O5‐catalyzed condensation reaction of both benzamide and benzonitrile to form 1,3,5‐triphenyl‐2,4,6‐triazine in high yield.