Breakthrough Experiments Research Articles

Cooperative lattice theory for CO2 adsorption in diamine-appended metal-organic framework at humid direct air capture conditions

The effect of humidity on the cooperative adsorption of CO2 from the air on amine-appended metal–organic frameworks is studied both experimentally and theoretically. Breakthrough experiments show that, at low relative humidities, there is an anomalous induction effect, where the kinetics at short times are slower than kinetics at long times. The induction effect gradually vanishes as relative humidity is increased, corresponding to an increase in CO2 adsorption rate. A new theory is proposed based on the lattice kinetic theory (LKT), which explains these experimental results. LKT can accurately represent the measured data over the full range of humidities by postulating that the presence of adsorbed water shifts the equilibrium clusters from cooperatively bound chains to non-cooperatively bound CO2. A consequence of this transition is that CO2 exhibits step adsorption isotherm in dry air and a standard Langmuir adsorption isotherm in high humidity air.

Mechanically robust MOF beads for efficient ethylene/ethane separation with fast adsorption kinetics

Shaping of metal–organic frameworks (MOFs) without obvious mass transfer resistance is crucial for scaled-up adsorption separation process. Herein, mechanically robust ultramicroporous MOF (ZU-901, also termed CPL-1-CH3) beads with hierarchical porosity were structured through the calcium alginate (CA) method, which preserved the adsorption separation performance and demonstrated fast gas diffusion rates. The highly crosslinked networks of CA contributed to the excellent mechanical properties of 95 % ZU-901@CA beads with Young’s modulus up to 1.81 MPa and a low abrasion rate of 0.32 %, superior to that of 95 % ZU-901@HPC extrudates (1.13 %). Compared with powder of ZU-901, the C2H4 uptake capacity of ZU-901@CA beads showed only 3 % loss at 298 K. The C2H4 diffusion time constant of 95 % ZU-901@CA beads (7.06 × 10−3 s−1) was comparable to that of the powders (7.61 × 10−3 s−1) and higher than that of ZU-901@HPC extrudates (2.95 × 10−3 s−1). Breakthrough experiments confirmed that ZU-901@CA beads performed well in the dynamic separation of C2H4/C2H6 binary mixture, and could be easily regenerated at room temperature. In addition, after post modification on the exterior of ZU-901 beads, the water contact angle increased from 0° to 119°. Therefore, the mechanically robust ZU-901@CA beads showed great potential in energy-efficient C2H4/C2H6 separation.

Multiple Structural and Phase Transformations of MOF and Selective Hydrocarbon Gas Separation in its Amorphous, Glass Phase States

AbstractThe first wide‐view image of multiple structural and phase transformations for MOFs, ranging from crystal state transformations to the extreme limit approaching liquid/glass phase, was presented. The process involves i) an initial crystalline transformation from square‐layer framework [Co2(pybz)2(CH3COO)2] ⋅ DMF (Co2) to a 3‐fold interpenetrated and ordered vacancies contained framework [Co(pybz)2(CH3OH)2] ⋅ 2CH3OH (CoM) due to in situ disassemble‐reassemble, ii) thermal induced departure of a pair of cis‐form coordinated methanol in CoM leads to amorphous framework a‐dCoM, iii) glass transition to super‐cooled liquid scl‐dCoM, iv) obtaining MOF glass g‐dCoM upon quenching the super‐cooled liquid, and v) re‐crystallization of super‐cooled liquid generates 6‐fold interpenetrated dia‐net framework [Co(pybz)2]6n (rec‐dCoM) under further heating. The access to glass from CoM, provides a new self‐perturbation strategy to create MOF glasses without melting. The wider pore size distribution in amorphous/glassy MOFs than crystalline precursor achieved the first time selective hydrocarbon gas separation by breakthrough experiments, which bring efficient separation of 1 : 99 C2H2/C2H4 by either a‐dCoM or g‐dCoM and produce polymer grade C2H4 with purity≥99.5 % after a single adsorption process. Furthermore, the mixture of 50 : 50 C3H6/C3H8 can be separated by a‐dCoM.

Trace benzene capture by decoration of structural defects in metal-organic framework materials.

Capture of trace benzene is an important and challenging task. Metal-organic framework materials are promising sorbents for a variety of gases, but their limited capacity towards benzene at low concentration remains unresolved. Here we report the adsorption of trace benzene by decorating a structural defect in MIL-125-defect with single-atom metal centres to afford MIL-125-X (X = Mn, Fe, Co, Ni, Cu, Zn; MIL-125, Ti8O8(OH)4(BDC)6 where H2BDC is 1,4-benzenedicarboxylic acid). At 298 K, MIL-125-Zn exhibits a benzene uptake of 7.63 mmol g-1 at 1.2 mbar and 5.33 mmol g-1 at 0.12 mbar, and breakthrough experiments confirm the removal of trace benzene (from 5 to <0.5 ppm) from air (up to 111,000 min g-1 of metal-organic framework), even after exposure to moisture. The binding of benzene to the defect and open Zn(II) sites at low pressure has been visualized by diffraction, scattering and spectroscopy. This work highlights the importance of fine-tuning pore chemistry for designing adsorbents for the removal of air pollutants.

A Stable Layered Microporous MOF Assembled with Y-O Chains for Separation of MTO Products.

Benefiting from highly tunable pore environments, some metal-organic frameworks (MOFs) have recently shown promising prospects in the separation of methanol-to-olefin (MTO) products (mainly C3H6 and C2H4). However, the "trade-off" between gas storage capacity and selectivity always results in inefficient separation. In addition, poor stability of MOFs also limits practical separation applications. Herein, we have successfully assembled a layered Y-MOF (FJI-W9) with bent diisophthalate ligands (H4L), Y-O chains, and 2-fluorobenzoic acids. As expected, FJI-W9 not only exhibits good chemical stability but also shows significant potential for C3H6/C2H4 separation. For FJI-W9, the C3H6 uptake at 298 K and 10 kPa is 63 cm3/g, and the IAST selectivity of FJI-W9 for C3H6/C2H4 (V/V = 50/50) is calculated to be 20.5. To the best of our knowledge, both C3H6 uptake and selectivity of FJI-W9 surpass most porous materials. GCMC simulation indicates that the special supramolecular binding sites in FJI-W9 have much stronger interactions with C3H6 than C2H4 molecules. More importantly, practical breakthrough experiments demonstrate that FJI-W9 can effectively separate C3H6/C2H4 (50/50) mixtures, thus obtaining high-purity C2H4 and C3H6, respectively.

Irrigation Water Salinity Affects Solute Transport and Its Potential Factors Influencing Salt Distribution in Unsaturated Homogenous Red Soil

As a promising alternative water source to alleviate irrigation water scarcity in red soil regions in southern China, low-quality water could enhance regional water resource utilization and promote sustainable agriculture. However, its soluble salt and ions could affect soil solute distribution and transport, potentially hindering crop growth. Undoubtedly, it is necessary to understand the mechanism of solute transport in red soil under low-quality water irrigation with different water salinity levels. Therefore, a one-dimensional vertical water infiltration experiment and a solute breakthrough experiment were conducted to evaluate the solute transport (soluble salt, Na+, and Cl−) in unsaturated and saturated homogenous red soil at different salinity levels [1 (S1), 2 (S2), 3 (S3), 5 (S5), and 10 (S10) g/L] when irrigated with simulated low-quality water using analytical-grade NaCl. Moreover, the potential factors affecting salt distribution in unsaturated red soil were determined. The findings indicate positive linear relationships between accumulations of three solutes and irrigation water salinity. Generally, the depth of maximum solute concentration increased with the increase in irrigation water salinity. Soluble salt, Na+, and Cl− exhibited early breakthrough and trailing in red soil, but higher irrigation water salinity could reduce PV and retardation. A mobile and immobile water model (MIM) showed that convection was dominant in solute transport in red soil under low-quality water irrigation. D decreased as a power function with increasing irrigation water salinity, while v and R decreased linearly. Furthermore, the red soil can adsorb Cl− resulting from its special charge characteristics under low-quality water irrigation, which may be the main source of salt adsorption. Additionally, v &gt; soil pH &gt; βsalt primarily influenced salt distribution in the 0–40 cm soil profile. This study can provide insights into solute transport in red soil under low-quality water irrigation, facilitating soil fertility and structure, as well as low-quality water irrigation strategy optimization.

Construction of a Fluorinated-Anion Pillared Metal-Organic Framework Exhibiting Dual-Pore Architecture for Simultaneous Enhancement of C2H2 Adsorption Capacity and Selectivity.

Physisorption-based separation processes represents a promising alternative to the conventional thermally driven methods, such as cryogenic separation. However, a significant challenge lies in balancing the trade-off between adsorption capacity and selectivity of adsorbents. In this study, we introduce a novel fluorinated-anion pillared metal-organic frameworks (APMOFs) featuring a dual-pore architecture, constructed using a pyridine-oxazole bifunctional ligand. The inherent low symmetry of the ligand leads to significant distortion of the fluorinated-anion pillars, resulting in a distinctive type of APMOFs characterized by dual-pore architecture. On pore structure with constrict pore width is enriched with a high density of anion fluorinated pillars, offering numerous active sites advantageous for enhancing separation selectivity. Concurrently, the other pore structure exhibits larger dimensions, facilitating increased gas molecule accommodation and thereby augmenting adsorption capacity. Gas sorption studies reveal a substantial C2H2 adsorption capacity and a high C2H2/CO2 separation selectivity. Breakthrough experiments confirm its exceptional separation performance, while theoretical investigations elucidate a sequential adsorption process within these APMOFs, underscoring the efficacy of this strategy in overcoming trade-off limits in adsorbents.

CO2 capture enhancement by metal oxides impregnated coal fly ash: a breakthrough adsorption study.

Coal fired power plants are significant contributors to CO2 emissions and produce solid waste in the form of coal fly ash, posing severe environmental challenges. This study explores the application of dry-impregnated coal fly ash for CO2 capture from gas stream. The modification of coal fly ash was achieved using alkaline earth metal oxides, specifically CaO and MgO, to alter its physical and chemical properties. Characterization techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET (Brunauer-Emmett-Teller) analysis were employed for physio-chemical changes in the adsorbent. Breakthrough experiments were conducted using a laboratory-scale fixed packed-bed reactor to assess the influence of temperature and gas flow rate on CO2 adsorption. Among the synthesized sorbents, calcium oxide-impregnated ash showed the highest CO2 uptake capacity, achieving 9.41mg/g at 30°C and a flow rate of 20 L/hr under atmospheric pressure. Isotherm modeling indicated a heterogeneous adsorbent surface, with the data best fitting the Sips isotherm model. Furthermore, the adsorption data conformed well to the Yoon-Nelson and Thomas kinetic models, affirming their relevance in characterizing the adsorption process under varying conditions. This research emphasizes the potential of coal fly ash-an abundant, cost-free material-as an effective CO2 adsorbent, contributing to both CO2 mitigation and landfill waste reduction.

Room-Temperature Synthesis of a Fluorine-Functionalized Nanoporous Organic Polymer for Highly Efficient SF6 Adsorption and Separation.

Sulfur hexafluoride (SF6) is widely used in the power industry and significantly contributes to the greenhouse effect, necessitating the development of efficient materials for SF6 capture, particularly fluorine-containing materials. However, existing fluorine-containing materials often require complex monomers and high synthesis temperatures. Herein, we report the synthesis of a fluorine-functionalized carbazole-based nanoporous organic polymer (CNOP-7) at room temperature, using commercially available 4,4'-bis(9H-carbazole-9-yl)-1,1'-biphenyl and 1,1,1-trifluoroacetone. CNOP-7 contains 14.7% fluorine atoms and exhibits a high specific surface area of 1270 m2·g-1, demonstrating excellent SF6 adsorption and separation performance. The SF6/N2 selectivity of CNOP-7 reaches 107 at 273 K and 73 at 298 K. Furthermore, dynamic breakthrough experiments confirm that CNOP-7 can efficiently and repeatedly separate SF6 from SF6/N2 mixtures. Molecular simulations reveal the mechanism behind its efficient separation. This work offers fresh perspectives on the development and fabrication of adsorbents for efficient SF6 sequestration.

Fabricating a Robust Ultramicroporous Metal-Organic Framework for Purifying Natural Gas and Coal Mine Methane.

Purifying methane (CH4) from natural gas and coal mine methane (CMM) is of great significance but challenging in the chemical industry. Herein, a robust ultramicroporous metal-organic framework (MOF) is reported, which can be synthesized on a gram scale by stirring under room temperature. Single-component adsorption isotherms of gases (CH4, ethane (C2H6), propane (C3H8), nitrogen (N2)) and breakthrough experiments indicate that the MOF can separate CH4 efficiently from CH4/C2H6/C3H8 ternary mixture, with super high purity-CH4 production of 154.7 cm3g-1. Additionally, the MOF shows higher CH4 capacity than N2, resulting in excellent separation performance for the CH4/N2 mixture. Notably, the binding sites of gases can be precisely determined by single-crystal X-ray data, further confirmed by molecular simulation. It is found that there are multiple hydrogen bonds and C─H···π interactions between the gases and the framework. This work offers an excellent candidate material for CH4 purification with both high capacity and separation efficiency.

Six-Membered Ring Directed Assembly of a Zirconium Zeolitic Metal-Organic Framework for Efficient Separation of Hexane Isomers.

The synthesis of zirconium MOFs with zeolite net is quite challenging due to the high connectivity of Zr6 clusters, which is far from tetrahedral connection, a requisite for zeolite net. In this work, we demonstrate a six-membered ring (6MR) strategy through mimicking of mineral zeolites with mixed ditopic and tritopic carboxylate linkers. With this strategy, the ditopic linker cross-links Zr6 clusters to form 4-connected zeolite-like nets, while the tritopic one is used to direct the formation of 6MR and simultaneously consumes extra coordination sites on the cluster. The feasibility of this strategy is shown by one zeolitic metal-organic framework (NNM-5) and this strategy has also led to the synthesis of the other dia-type zirconium MOF (NNM-6). Interestingly, as the tritopic linker not only directs the formation of 6MR but also partitions 6MR into small segments, NNM-5 with SOD topology shows a structural feature of small aperture and big cage, which has led to efficient separation of hexane isomers. With both exceptionally high n-hexane uptake (65.9 cm3 g-1) and size-exclusion selectivity, an exceptional separation capability is verified by breakthrough experiments. Calculation results demonstrate that the large difference of diffusion energy barrier due to the small aperture accounts for the underlying separation mechanism.

Compatible alignment of pore electro-fields for enhanced one-step ethylene purification from ternary gas mixtures

The one-step purification of ethylene (C2H4) from ternary gas mixtures containing acetylene (C2H2), carbon dioxide (CO2), and C2H4 represents an efficient approach. It remains a significant challenge to simultaneously enhance the adsorption capacities of C2H2 and CO2. Herein, we reported a novel adsorbent, BFFOUR-TEPE-Cu, with compatible alignment of pore electro-fields. The one-connected BF4- anions provide more electronegative F atoms to reinforce the alignment of compatible electro-fields, thereby promoting the preferential adsorption of C2H2 and CO2 over C2H4. As a result, BFFOUR-TEPE-Cu exhibits a leading C2H2 capacity of 63.0 cm3 g−1 and C2H2/C2H4 (1/99, v/v) selectivity of 31.1 at 0.1 bar and 298 K. Computational studies reveal the favorable capture of both C2H2 and CO2 due to the compatible electron-fields. Dynamic breakthrough experiments demonstrate the exceptional capability for one-step production of high-purity C2H4 (>99.99 %) from ternary C2H2/CO2/C2H4 (1/9/90) gas mixture with a C2H4 productivity of 3.4 mol kg−1.

Revving Up a Designed Copper Catecholate Porous Organic Polymer for Its Potent Ethylene Adsorption than Ethane.

The potential to produce high-purity C2H4 has made ethylene-selective adsorbents for ethane (C2H6)/ethylene (C2H4) gas mixture separation appealing as viable substitutes for traditional cryogenic distillation. In this aspect, porous organic polymers (POPs) are anticipated to become the next-generation potential adsorbent due to their easily customizable functions and functional sites suitable for gas separation. This article reports the selective C2H4 adsorption over C2H6 using microporous copper(I)-coordinated POP (Cu@Di-POP) via fine-tuning of the π complexation and pore size. The specially designed adsorbent has the ideal pore size and coordinated Cu(I) ions to form π-complexation with C2H4 molecules, which enabled it to adsorb C2H4 (at 1 bar, 24.9, 18.9, and 13.4 cm3 g-1 at 273, 298, and 323 K, respectively) while significantly reducing C2H6 adsorption (at 1 bar, 16.9, 12.7, and 8.8 cm3 g-1 at 273, 298, and 323 K, respectively). At 1 bar, Cu@Di-POP exhibited IAST selectivities of 6.09, 5.60, and 4.13 for C2H4/C2H6 at 273, 298, and 323 K, respectively, suggesting its C2H4 selective behavior, which was further confirmed from the experimental breakthrough measurement. Furthermore, the computational studies carried out with density functional theory highlighted an enhanced charge distribution leading to dπ-pπ conjugation between C2H4 π-electrons and Cu d-electrons, thereby showing a relatively higher interaction energy of -37.23 kcal/mol with C2H4 as compared to -16.06 kcal/mol with C2H6 gas molecules.

Synergistic C2H2 Binding Sites in Hydrogen-Bonded Supramolecular Framework for One-Step C2H4 Purification from Ternary C2 Mixture.

Purification of C2H4 from the ternary C2 hydrocarbon mixture in one step is of critical significance but still extremely challenging according to its intermediate physical properties between C2H6 and C2H2. Hydrogen-bonded organic frameworks (HOFs) stabilized by supramolecular interactions are emerging as a new kind of adsorbents that facilitate green separation. However, it remains a problem to efficiently realize the one-step C2H4 purification from C2H6/C2H4/C2H2 mixture because of the low C2H2/C2H4 selectivity. We herein report a robust microporous HOF (termed as HOF-TDCPB) with dense O atoms and aromatic rings distributed on the pore surface which provide C2H6 and C2H2 preferred environment simultaneously. Dynamic breakthrough experiments indicate that HOF-TDCPB can not only obtain high-purity C2H4 from binary C2 mixture, but also firstly realize one-step C2H4 purification from ternary C2H6/C2H4/C2H2 mixture, with the C2H4 productivity of 3.2 L/kg (>99.999 %) for one breakthrough cycle. Furthermore, HOF-TDCPB displays outstanding stability in air, organic solvents and water, which endow it excellent cycle performance even under high-humidity conditions. Theoretical calculations indicate that multiple O sites on pore channels can create synergistic binding sites for C2H2, thus affording overall stronger multipoint interactions.

Bioinspired recognition in metal-organic frameworks enabling precise sieving separation of fluorinated propylene and propane mixtures

The separation of fluorinated propane/propylene mixtures remains a major challenge in the electronics industry. Inspired by biological ion channels with negatively charged inner walls that allow selective transport of cations, we presented a series of formic acid-based metal-organic frameworks (MFA) featuring biomimetic multi-hydrogen confined cavities. These MFA materials, especially the cobalt formate (CoFA), exhibit specific recognition of hexafluoropropylene (C3F6) while facilitating size exclusion of perfluoropropane (C3F8). The dual-functional adsorbent offers multiple binding sites to realize intelligent selective recognition of C3F6, as supported by theoretical calculations and in situ spectroscopic experiments. Mixed-gas breakthrough experiments validate the capability of CoFA to produce high-purity (>5 N) C3F8 in a single step. Importantly, the stability and cost-effective scalable synthesis of CoFA underscore its extraordinary potential for industrial C3F6/C3F8 separations. This bioinspired molecular recognition approach opens new avenues for the efficient purification of fluorinated electronic specialty gases.

Synergistic C2H2 Binding Sites in Hydrogen‐Bonded Supramolecular Framework for One‐Step C2H4 Purification from Ternary C2 Mixture

AbstractPurification of C2H4 from the ternary C2 hydrocarbon mixture in one step is of critical significance but still extremely challenging according to its intermediate physical properties between C2H6 and C2H2. Hydrogen‐bonded organic frameworks (HOFs) stabilized by supramolecular interactions are emerging as a new kind of adsorbents that facilitate green separation. However, it remains a problem to efficiently realize the one‐step C2H4 purification from C2H6/C2H4/C2H2 mixture because of the low C2H2/C2H4 selectivity. We herein report a robust microporous HOF (termed as HOF‐TDCPB) with dense O atoms and aromatic rings distributed on the pore surface which provide C2H6 and C2H2 preferred environment simultaneously. Dynamic breakthrough experiments indicate that HOF‐TDCPB can not only obtain high‐purity C2H4 from binary C2 mixture, but also firstly realize one‐step C2H4 purification from ternary C2H6/C2H4/C2H2 mixture, with the C2H4 productivity of 3.2 L/kg (&gt;99.999 %) for one breakthrough cycle. Furthermore, HOF‐TDCPB displays outstanding stability in air, organic solvents and water, which endow it excellent cycle performance even under high‐humidity conditions. Theoretical calculations indicate that multiple O sites on pore channels can create synergistic binding sites for C2H2, thus affording overall stronger multipoint interactions.

High Performance of the Metal Organic Framework CPO‐27 for Toxic Gas Capture (NO2)

AbstractMetal‐organic frameworks of the CPO‐27 (MOF‐74) series are known for their high adsorption capacities for nitrogen oxides. On the other hand, significantly varying and partly contradictory results were reported regarding their stability to moisture. This aspect has hampered the use of these MOFs in air filtration applications. Here, we show that the stability of CPO‐27 materials towards moisture and CO2 crucially depends on the synthesis parameters. By precisely adjusting the synthetic parameter‐property relationship, it is possible to prepare a highly stable CPO‐27(Ni) MOF by a simple precipitation in water. To demonstrate the capacity for NO2, breakthrough experiments were performed under dry and wet conditions (55% relative humidity). Extremely high values of nearly 0.74 g/g in dry conditions and 1.23 g/g under wet conditions were achieved. These results pave the way for the toxicologically safe and cost‐effective preparation of a moisture‐stable CPO‐27(Ni), bridging the gap to a potential industrial application of the material for the selective adsorption of toxic gases, such as NO2.

Synthesis of porous hypercrosslinked polymers from waste polystyrene for efficient CO2 separation

A series of porous hypercrosslinked polymers (HCP-x) were synthesized from waste polystyrene foam via Fridel-Crafts alkylation reaction, aiming to optimize the utilization of waste plastics. The impact of various crosslinkers on the structural characteristics and CO2 adsorption properties of HCP-x was investigated. The results indicated that HCP-x polymers possess high specific surface areas spanning 830–1182 m2 g−1, abundant narrow micropores, and exceptional thermal stability. Notably, HCP-2 exhibited the highest CO2 adsorption capacity of 2.77 mmol g−1 at 273 K and 1.0 bar. These hypercrosslinked polymers also demonstrated a favorable CO2/N2 ideal selectivity and robust cyclic adsorption performance. Breakthrough experiments confirmed the selective adsorption of CO2 from simulated flue gas containing CO2/N2 (15/85). Additionally, the mechanism underlying CO2 adsorption on HCP-x was elucidated by analyzing adsorption thermodynamics and diffusion kinetics. This study not only introduces an innovative method for recycling waste polystyrene foam but also underscores the potential of HCP-x as an effective adsorbent for CO2 capture.

Engineering Nanoporous Polyaminal Networks for Superior SO2 Capture and Selectivity.

Designing adsorbent materials with high SO2 adsorption capacities and selectivity remains a significant challenge in flue gas desulfurization. This work focuses on developing two nitrogen-rich nanoporous polyaminal networks (NPANs), which demonstrate promising capabilities for SO2 adsorption and separation. Two nitrogen-rich nanoporous polyaminal networks, NPAN-5 and NPAN-6, were synthesized via a one-pot method using thiophene-2,5-dicarbaldehyde and furan-2,5-dicarbaldehyde with 1,4-bis(2,4-diamino-1,3,5-triazine)-benzene, respectively. The Brunauer-Emmett-Teller (BET) specific surface areas of NPANs range from 838 to 956 m2·g-1. At 298 K and pressures of 0.1 and 1.0 bar, NPAN-5, featuring thiophene units, demonstrates a SO2 adsorption uptake of 5.14 and 9.63 mmol·g-1, respectively, surpassing many previously reported materials. Furthermore, at room temperature, NPAN-6, containing furan moieties, exhibits unprecedented selectivity for SO2 over CO2 and N2, with ratios reaching up to 78 and 9321, respectively. Dynamic breakthrough experiments reveal that NPANs effectively separate SO2 from a ternary gas mixture comprising SO2, CO2, and N2 at concentrations of 0.2, 10, and 89.8%, respectively. Notably, NPAN-6 achieves a prolonged SO2 retention time of 218 min·g-1 and a saturation adsorption uptake of 0.42 mmol·g-1. The remarkable SO2 adsorption capacities and selectivities demonstrated by these nitrogen-rich nanoporous polyaminal networks underscore their potential to revolutionize industrial flue gas desulfurization.

Preparation of highly graphitized porous carbon and its ethane/ethylene separation performance

The efficient separation of ethane (C2H6) and ethylene (C2H4) is crucial for the preparation of polymer-grade C2H4, necessitating the development of highly selective and stable C2H6/C2H4 adsorbents. Highly graphitized porous carbon, denoted GC-800, was synthesized by polymerization at room temperature followed by carbonization at 800 °C using phenolic resin as the precursor and FeCl3 as the iron source. Vienna Ab-initio Simulation Package (VASP) calculations confirmed a higher binding energy between C2H6 molecules and graphitized porous carbon surfaces, so that a high degree of graphitization increased the adsorption capacity of porous carbon for C2H6. However, catalytic graphitization using Fe at high temperatures disrupted the microporous structure of the carbon, thereby reducing its ability to separate C2H6/C2H4. By controlling the carbonization temperature, the degree of graphitization and pore structure of the porous carbon could be changed. Raman spectra and XPS spectra showed that the GC-800 had a high degree of graphitization, with a sp2 C content as high as 73%. Low-temperature N2 physical adsorption measurements estimated the specific surface area of GC-800 to be as high as 574 m2·g−1. At 298 K and 1 bar, it had an equilibrium adsorption capacity of 2.16 mmol·g−1 for C2H6, with the C2H6/C2H4 (1:1 and 1:9, v/v) ideal adsorbed solution theory selectivity respectively reaching 2.4 and 3.8, significantly higher than the values of most reported high-performance C2H6 selective adsorbents. Dynamic breakthrough experiments showed that GC-800 could produce high-purity C2H4 in a single step from a mixture of C2H6 and C2H4. Dynamic cycling tests confirmed its good cyclic stability, and that it could efficiently separate C2H6/C2H4 even under humid conditions.