Dynamic Adsorption Capacity Research Articles

Superior pore size for enhancing the competitive adsorption of VOCs under high humid conditions: An experiment and molecular simulation study

Water vapor greatly decreases the adsorption capacity of activated carbons (AC) for low-concentration volatile organic compounds (VOCs) under high humid conditions. However, the design and synthesis of AC with high adsorption selectivity for VOCs/water vapor still remains a challenge. In this paper, a hydrophobic hierarchical porous AC was synthesized by using g-C3N4 as the pore-forming agent and the roles of pore sizes on the competitive adsorption were studied by experiments and simulation calculations. The results showed that pore size of 0.59–1.50 nm had a stronger correlation with toluene dynamic adsorption capacity. The largest adsorption capacity of single toluene and water vapor occurred in the 1.0 nm and 0.7 nm slit pore, respectively. During the toluene adsorption at 70 RH%, the superior pore size was 0.7–1.30 nm, and the maximum value appeared in the 1.0 nm pore without pore condensation of water clusters. Furthermore, a quantitative relationship that the superior pore size of VOCs at 70 RH% was 0.86–1.52 S (S is the longest distance of VOCs molecule) was summarized. In addition, a lower surface oxidation degree would broaden superior pore size range. This study provides a theoretical preference for designing AC for target VOCs removal from high humid conditions.

Experimental and simulation study on the influence of pH on mono-molecular mechanical properties of benzene and graphene

In drug delivery systems, graphene materials are promising drug carriers. Drug molecules are loaded on graphene through π-π interaction between graphene and benzene ring structure, which is widely found in organic drug molecules. Then the drug molecules are released under different conditions, such as different environmental pH, at lesion site. In the application, the adsorption and desorption between benzene ring structure in drug molecules and graphene play a key role. Herein, an experimental method for measuring the adhesion force between a single phenyl and graphene is proposed, and the adsorption and desorption mechanical properties of a benzene ring structure on graphene surface at different environmental pH are firstly measured. The experimental results show that the adhesion force decreases with the increase of environmental pH. Moreover, molecular dynamics simulations show that the influence of pH on adhesion force is mainly realized by changing the electrostatic potential distribution on graphene surface, and the interaction force between a single benzene and graphene changes from attractive to repulsive with the increase of environmental alkalinity. In addition, a molecular dynamics model for the dynamic adsorption and desorption capacities of benzene molecules on graphene surface at different quantity of ions is established. Benzene molecules can achieve full adsorption on the surface of graphene when there are 10 and 20 hydrogen ions. And benzene molecules can achieve full desorption on the surface of graphene when there are 10 and 20 hydroxide ions.

The preparation and adsorption performance of Co-doped MIL-101(Cr) for low-concentration C3F8

Octafluoropropane (C3F8) is a kind of super greenhouse gas, and the low concentration of octafluoropropane makes it difficult to be adsorbed and removed. In this study, a series of Co-doped MOFs (CoxCr-MIL-101) have been successfully synthesized using a hydrothermal method without the addition of strong acids such as HF. The structural properties of the prepared CoxCr-MIL-101 are characterized using SEM, XRD, nitrogen adsorption desorption test, etc. The adsorption properties of C3F8 are measured by single-component isothermal adsorption experiments and fixed bed adsorption breakthrough experiments. The adsorption mechanism was investigated via the adsorption theory models. The results show that the introduction of cobalt ions can effectively improve the adsorption capacity of MIL-101, among which the Co0.2Cr-MIL-101 exhibits the best adsorption performance. The C3F8 equilibrium adsorption capacity reaches 0.077 mmol/g at 298 K and 180 Pa, which is 3.03 times that of the pristine MIL-101 and the dynamic adsorption capacity is 20.710 mmol/g (298 K, 1.2 L/min), which is 9.37 times that of the pristine MIL-101. Inspiringly, the IAST separation selectivity of C3F8/N2 at 100 kPa is up to 146.7, which is 14.3 times that of the pristine MIL-101. More importantly, the co-modified adsorbent showed better thermal stability and cyclic stability. In addition, Co0.2Cr-MIL-101 fits the Freundlich isothermal adsorption model, and the adsorption mechanism analysis shows that the high adsorption capacity of Co0.2Cr-MIL-101 benefits from the unique pore structure and abundant active sites of the modified MOFs.

Development of a novel hierarchical porous and hydrophobic silica from montmorillonite for benzene adsorption

A hierarchical porous and hydrophobic adsorbent is the key to removing the volatile organic compounds through adsorption technology, especially under humidity conditions. In this work, we synthesized a hierarchical porous and hydrophobic montmorillonite-derived adsorbent by a facile strategy, i.e., a combination of ball milling, acid activation, and thermal treatment. Our results showed that ball milling could efficiently grind the montmorillonite sheets into small fragments, which caused the rapid dissolution of octahedral cations from the edges of these fragments during the subsequent acid activation process. The resulting porous silica showed more porosity (including micropores and mesopores) and a larger specific surface area (664 m2 g−1), compared with the product (345 m2 g−1) obtained by only acid washing without ball milling. The next thermal treatment readily removed the surface hydroxyl of porous silica, leading to the formation of the target product (HP-SiO2) with enhanced hydrophobicity and well-preserved pore structures. As an adsorbent for benzene molecules, HP-SiO2 exhibited a high dynamic benzene adsorption capacity (257.1 mg g−1) due to the large specific surface area and abundant micropores. Furthermore, HP-SiO2 maintained outstanding benzene adsorption performance under different humidity conditions (with a high adsorption capacity of 185.0 mg g−1 even under 40% relative humidity). Our work provided a low-cost and facile strategy for the synthesis of hierarchical porous and hydrophobic silica materials, and this adsorbent would serve as a promising adsorbent for the elimination of practical volatile organic compounds.

Designing pectin and hyperbranched polyethylene imine based hydrogel for the removal and adsorption of ionic dyes

In this study, we developed pectin based hydrogel modified with hyperbranched polyethylene imine integrated with graphene oxide as a filler for the removal of cationic and anionic dyes. Moreover, in this paper, we also studied dynamic adsorption capacity of hydrogel towards crystal violet dye. Graphene oxide was first prepared by the Hummers method. The result in this study illustrated that dynamic adsorption capacity of hydrogels enhanced with increase in GO concentration up to 192 mg g−1 this might be ascribed to the increase in active groups along with porosity created in hydrogel structure. Moreover, the change in parameters such as pH, salt concentration, flux rate and concentration of dye showed promising results. Hence the pectin based hydrogels have great potential for eradication of dyes.

Enhancements on volatile organic compounds (VOCs) adsorption and desorption performance of ZSM-5 by fabricating hierarchical MCM-41.

ZSM-5 zeolite has been considered a promising adsorbent for capturing VOCs. However, its hydrophilicity and narrow micropore structure limit their practical application especially under humid atmospheres. In this study, the pure silica mesoporous molecular sieve MCM-41 was assembled on ZSM-5 zeolite with different SiO2/Al2O3 ratios (SARs) via a surfactant-mediated recrystallization method. Then, its adsorption-desorption behaviors were investigated using n-hexane, toluene, and ethyl acetate as VOC model molecules. The results showed that the hydrophobicity of ZSM-5/MCM-41 composites and their VOC diffusion behaviors were significantly improved. Furthermore, the SARs of the ZSM-5 precursors had a remarkable influence on the adsorption performance of ZSM-5/MCM-41 composites. ZSM-5/MCM-41(130) was the optimum option, and its dynamic adsorption capacity for ethyl acetate (111.30 mg·g-1) was higher than that of the corresponding ZSM-5 zeolites even under statured humidity. Meanwhile, the ratios of dynamic adsorption capacities at humid and dry atmospheres (qs,wet/qs,dry) of ZSM-5/MCM-41(130) for n-hexane, toluene, and ethyl acetate were 84.89%, 61.46%, and 73.81% respectively. The results will provide guidelines for the preparation of hydrophobic adsorbents.

Dynamic adsorption behavior of 1.1.1.2-tetrafluoroethane (R134a) on activated carbon beds under different humidity and moisture levels

1.1.1.2-Tetrafluoroethane (R134a) is developed as a tracer for mechanical leakage detection in military chemistry. Due to the weaker physical adsorption properties, water vapor competitive adsorption limits the use of tracer R134a. Thus, it is urgent to the analyze dynamic competitive adsorption behavior of R134a and water vapor on the activated carbon. In this study, R134a breakthrough curves on the fixed beds packed with activated carbons under different relative humidity and moisture content levels were systematically measured. Combining mass spectrometry, gas chromatography, and a novel fiber Bragg grating temperature sensor, the dynamic competitive adsorption processes and axial temperature of fixed beds were first reported. Interestingly, with increasing moisture content, R134a breakthrough time decreased, but dynamic adsorption capacity increased. This was attributed to the fact that the residual water vapor could increase the specific surface area and pore volume of activated carbon to enhance R134a dynamic adsorption capacity. Using the R134a as the standard, the dynamic competitive adsorption process was first revealed and could be divided into four stages including Co-adsorption, Co-breakthrough, Competitive Adsorption (“Rolling Up” and “Adsorption Platform”), and Dynamic Adsorption Equilibrium. “Rolling Up” and “Adsorption Platform” phenomena are mainly determined by the strength of intermolecular interactions, the concentration difference of adsorbate, and the thermal effect induced by water vapor adsorption/desorption.

Electrospun nanofiber mat of graphene/mesoporous silica composite for wastewater treatment

In this research, we fabricated the electrospun nanofibers based on functionalized porous graphene (FPG), modified SBA-15 (SBA/CuO), Polyvinylpyrrolidone (PVP), and Polyacrylonitrile (PAN). FPG, SBA/CuO, and PAN concentrations, and applied voltage were optimized to fabricate the nanofibers with the best morphology. The average diameter of optimized nanofibers was obtained at 124 ± 41 nm. A series of characterizations, including FE-SEM, EDX, AFM, FT-IR, XRD, TG-DTA, tensile and contact angle measurements were employed to study the structure and morphology of nanofibers. We fabricated a Nano-filter from nanofibers to remove some water pollutants including methylene blue, malachite green, potassium permanganate, copper, lead, and cadmium ions. The filtration performance of the proposed Nano-filter was examined under the optimum conditions (concentration, volume, and pH) for each of the water pollutants (R> 97%). The results of Nano-filter recycling showed that it could be reused up to 5 times with more than 90% efficiency. Experiments have demonstrated that Nano-filter has ideal performance in the removal of dyes and metal ions from factory wastewater. Besides, the static and dynamic adsorption capacities were explored, where methylene blue (112 mg/g) and lead ions (131 mg/g) had higher static states were higher than other dyes and metal ions.

Exploring the differential effect of adsorption ingredients in three green sorption media for phosphorous removal from river water

In this study, three specialty adsorbents (i.e., green sorption media), clay-perlite and sand (CPS), zero-valent iron and perlite-based green environmental media (ZIPGEM), and biochar, zero valent iron, and perlite-based green environmental media (BIPGEM), were studied for their maximum phosphate adsorption capacity (qm) and their performance under different water matrices (i.e., pH of 4, 7, or 10 and canal water spiked with nitrate). The ZIPGEM media mix outperforms BIPGEM and CPS media in terms of phosphate adsorption capacity. According to the Langmuir isotherm model, the qm of ZIPGEM is 1.83, 1.80, 0.947 and 1.78 mg·g−1 at a water matrix of pH at 4, 7, or 10 and when using canal water spiked with nitrate, respectively. Moreover, we observed PO43− removal rates up to 99 % by ZIPGEM and BIPGEM regardless of the nature of the initial water matrix (pH variance and concurrent elements). Given the equivalent performance of BIPGEM and ZIPGEM, we conducted two fixed-bed column studies with ZIPGEM and CPS for further comparison of dynamic adsorption capacity in which CPS was the control. The predicted maximum adsorption capacity of ZIPGEM by the fixed-column study was estimated as 7.56 mg·g−1 in accordance with the Thomas dynamic model, which is higher than that of CPS (3.73 mg·g−1). Our results suggested that the sustainable and scalable nature of the proposed specialty adsorbent ZIPGEM with high phosphate adsorption capacity can be integrated into various water treatment processes. The high adsorption capacity of ZIPGEM can be mainly attributed to higher porosity and BET surface area of ZIPGEM.

CO2-assisted synthesis of graphitic resin-based activated carbon for ultrahigh selective adsorption of VOCs under humid conditions

Water vapor in the waste gases greatly reduce the VOCs adsorption capacity of adsorbents due to the competitive adsorption. Though chemical activation combined with catalytic graphitization was an available strategy for achieving both good graphitization and rich porosity to capture VOCs under humid conditions, it still remains a challenge of catalyst deactivation. This work developed a novel route to synthesize graphitic resin-based activated carbon (GRC) via CO2-assisted Fe-catalyzed graphitization and concurrent KOH activation. The selective adsorption behaviors of VOCs/water vapor were thoroughly investigated by static and dynamic adsorption experiments. The obtained GRC-10-A (5) displayed an outstanding graphitization degree, lower O content and hierarchical pore structure. This triggers a high dynamic adsorption capacity and a faster intra-particle diffusion both for toluene and 1,2-dichloroethane. For weak polar toluene, the adsorption selectivity quantized by Difference of Isosteric Heats equation was up to 69, exceeding strong polar 1,2-dichloroethane up to 12. Grand Canonical Monte Carlo simulations were used to explore the competitive adsorption mechanism from the perspective of surface oxygen groups (SOG) and pore size. The results revealed the main contributor to the excellent adsorption selectivity was a lower SOG content, which restricted the formation and pore condensation of water clusters. On the other hand, both the micropore overlap potential and molecular kinetic diameter determined the advantageous pore size ranges for different VOCs under humid conditions. These findings provide support for the fabrication and practical application of adsorbents in VOCs removal from humid conditions.

Quaternized polyethyleneimine-polyacrylonitrile crosslinked membrane with excellent performance synthetized by homogeneous strategy for efficient uranium extraction from seawater

The efficient extraction of uranium (U(VI)) from seawater has been a significant challenge for the nuclear industry. In this study, we prepared a robust quaternized polyethyleneimine-polyacrylonitrile crosslinked membrane (QPEI-PAN) using homogeneous cross-linking reaction and quaternary ammonium salt functionalization. PEI was uniformly dispersed inside the membrane by cross-linking with PAN molecular chains, providing QPEI-PAN with a robust structure and abundant active sites for U(VI) capture. The batch adsorption data obtained for QPEI-PAN modelled well using the Langmuir adsorption isotherm, and the maximum theoretical adsorption capacity was determined as 8198.2 mg·m−2. Particularly, QPEI-PAN reached a maximum dynamic adsorption capacity of 6823.1 mg·m−2 within 90 min. The robust membrane structure allowed for efficient regeneration, with a U(VI) recovery rate of 88 % over seven adsorption-desorption cycles. Quaternary ammonium salt functionalization not only gave the QPEI-PAN membrane an excellent anti-biofouling ability but also modified its surface charge, making it more suitable for the marine environment, where its adsorption capacity in unfiltered seawater (containing bacteria and microorganisms) was only 5.6 % lower than that of the filtered seawater. These findings suggest that this novel, anti-biofouling membrane-type adsorbent has significant potential for application in the field of uranium extraction from seawater (UES).

Hierarchical porous carbon with tunable apertures and nitrogen/oxygen heteroatoms for efficient adsorption and separation of VOCs

Porous carbon materials are good adsorbent candidates for removing volatile organic compounds (VOCs) due to their reliability and cost-effectiveness. Especially, the pore size distribution (PSD) of porous carbon materials plays a critical role in VOCs adsorption and separation. In this study, we present benzimidazole-derived porous carbons (BICs) with controllable pore size and oxygen/nitrogen heteroatoms. The pore size is controlled by adjusting the reaction degree of inorganic salt (K2CO3) and nitrogen-containing groups in the system. The tunable pore size distribution makes BICs highly efficient for the adsorption and separation of VOCs. BIC-3-900 exhibits a dominant pore size distribution of 3.0–4.0 nm and an exceptionally high total pore volume of 2.42 cm3/g, leading to ultra-high adsorption capacities for benzene and methanol (22.19 and 52.65 mmol/g, respectively) at 293 K. In addition, BIC-1-700 dominated by the micropore size is more favorable for adsorbing low-concentration small molecule VOCs (with a dynamic adsorption capacity of 4.21 mmol/g for methanol at 3800 ppm). In terms of the adsorptive separation performance, BIC-1-900 has an efficient benzene/methanol selectivity (∼30.13) due to its PSD (1.2–2.0 nm) which was more favorable for capturing low-concentration benzene. Moreover, both experimental and simulation (GCMC and DFT) results demonstrate that the abundant N/O heteroatoms doping in BIC-1-700 results in charge heterogeneity and stronger electrostatic affinity for polar VOCs molecules. Herein, our findings suggest that BICs with controllable pore size and oxygen/nitrogen heteroatoms have significant potential in practical VOCs capture and separation.

Carbon capture from humid gases using alkaline-promoted polypyrrole by a vacuum swing adsorption process

Post-combustion carbon capture from humid flue gas is one of the urgent research projects for achieving the target of carbon neutrality in near future. Nitrogen-containing polymers are considered as a promising adsorbent for carbon capture in flue gases due to their potential water resistance. Here, two-step synthesis of alkaline-promoted polypyrrole (AP-PPy) with water resistance was investigated as an adsorption material for carbon capture and separation. It was found from chemical and physical analysis that the alkaline-promoted sample kept the similar morphological structure as the pristine polypyrrole but possessed more amino groups. The adsorption of single component gases revealed that the adsorption amounts of CO2, CH4, and N2 were 1.31, 0.28 and 0.065 mmol/g at 303 K respectively, among which the CO2 uptake was 80% higher compared with the original polypyrrole. The breakthrough point of AP-PPy in moisture is comparable to that of dry mixture, but the dynamic CO2 adsorption capacity is calculated to be larger than that of dry condition. A single-bed three-step vacuum swing adsorption cycling device was constructed in the laboratory and the effect of adsorption time, vacuum pressure and feed flowrate on product purity and recovery were explored with over 50 cycles in each condition to ensure cyclic steady adsorption, thereby also verifying the recyclability of AP-PPy. The excellent CO2 adsorption and separation properties demonstrated that AP-PPy can be a promising material for post combustion carbon capture.

Polyphosphonate-segmented macroporous organosilicon frameworks for efficient dynamic enrichment of uranium with in-situ regeneration

Efficient separation and enrichment of uranium from radioactive effluents is of strategic significance for sustainable development of nuclear energy and environmental protection. Macropore structure of adsorbent is conducive to accessibility of the pore and transport of the adsorbate during dynamic adsorption. However, the low specific surface area results in fewer ligand sites and subsequently reduces the adsorption capacity. Herein, we present a novel strategy for efficient dynamic uranium enrichment using polyphosphonate-segmented macroporous organosilicon frameworks (PMOFs). PMOFs are constructed through the copolymerization of diethyl vinylphosphonate and triethoxyvinylsilane, followed by hydrolysis and condensation of the oligomers. The introduction of polyphosphonate segments into the frameworks endows PMOFs with a macroporous structure (31 µm) and a high ligand content (up to 72 wt%). Consequently, the optimized PMOF-3 demonstrated an ultrahigh dynamic adsorption capacity of 114.8 mg/g among covalently conjugated silicon-based materials. Additionally, PMOF-3 achieves a high enrichment factor (120) in the dynamic enrichment of uranium on a fixed bed column, which can be in-situ regenerated with 1 M NaHCO3 as the eluent. This work presents a new strategy for efficient dynamic enrichment of nuclides, which can be extended to the separation of other specific pollutants, shedding new light on adsorbent design and technical innovation.

Synthesis of corncob biochar with high surface area by KOH activation for VOC adsorption: effect of KOH addition method

AbstractBACKGROUNDCarbon materials have been regarded as valuable adsorbents for removal of volatile organic compounds (VOCs) owing to their high specific surface area and abundant pore structure. However, the complexity and high cost of the process used to treat the feedstock to produce commercial activated carbon has limited its application. In this reported study, a series of biochar materials was prepared using the KOH modification method employing corn cob as the raw material. The effects of different potassium hydroxide dosages, various activation temperatures and the activator addition method on the structure, physicochemical properties and VOC adsorption performance of the resulting biochars and their structure–activity relationship were systematically studied.RESULTSAdsorption performance tests and a series of characterization results showed that the CC‐3‐700 (corn cob/KOH = 1:3, T = 700 °C, two‐step dry mixing pyrolysis method) sample had highest toluene dynamic adsorption capacity (up to 573.5 mg g−1) compared to the other prepared samples. This result was attributed to the maximum specific surface area (2349 m2 g−1) and pore volume (1.22 cm3 g−1) of this sample. Moreover, the result suggested that the high specific surface area, abundant pore structure and highly disordered non‐graphitizable carbon in sample CC‐3‐700 were the major reasons for its excellent adsorption performance. The results of a multi‐component adsorption performance test showed that corn cob biochar had a strong adsorption capacity for toluene when simultaneously exposed to benzene and toluene.CONCLUSIONThe results of this study revealed that the corn cob biochar prepared using a two‐step roasting method offers good potential prospects for application in the field of VOC pollution control. © 2023 Society of Chemical Industry (SCI).

Design, preparation, and application of novel multilayer metal-polyphenol composite on macroporous framework melamine foam for effective filtration removal of tetracycline in fluidic systems

Effective capture of antibiotic residues from different fluidic sources is still a challenge in dealing with existence of the chemicals in nature, especially with presence of other pollutants and suspended solids in the systems. Here, we report preparation of a novel macroporous metal − polyphenol/melamine foam (MF) composite (FTBS@MF) as a filtration matrix. The FTBS@MF matrix has rapid and effective adsorption to tetracycline (TC) in aqueous systems and could provide 99% TC removal efficiency from wastewater with a maximum capacity (650 mg·g−1) within 30 min. The TC adsorption on FTBS@MF are basically via multiple types of chemical interactions between TC and the functionalized MF surfaces, these mechanisms were confirmed by confocal imaging, XPS and fluorescence spectra. The FTBS@MF could reach 100% removal of TC at a flow rate 60 mL·h−1 with a dynamic adsorption capacity 600 mg·L−1. Furthermore, the FTBS@MF showed proper thermal and chemical stability and reusability of up to 20 cycles of reuses, and the recycling process was environmentally friendly. In addition, the FTBS@MF showed >95% removal efficiency of TC from real milk and dairy manure wastewater through a dynamic adsorption system. The macroporous framework matrix with rapid and efficient removal of antibiotics from milk and wastewater present great potential for practical applications of removing other emerging pollutants from various fluidic streams.

On the Performance of a Ready-to-Use Electrospun Sulfonated Poly(Ether Ether Ketone) Membrane Adsorber.

Motivated by the need for efficient purification methods for the recovery of valuable resources, we developed a wire-electrospun membrane adsorber without the need for post-modification. The relationship between the fiber structure, functional-group density, and performance of electrospun sulfonated poly(ether ether ketone) (sPEEK) membrane adsorbers was explored. The sulfonate groups enable selective binding of lysozyme at neutral pH through electrostatic interactions. Our results show a dynamic lysozyme adsorption capacity of 59.3 mg/g at 10% breakthrough, which is independent of the flow velocity confirming dominant convective mass transport. Membrane adsorbers with three different fiber diameters (measured by SEM) were fabricated by altering the concentration of the polymer solution. The specific surface area as measured with BET and the dynamic adsorption capacity were minimally affected by variations in fiber diameter, offering membrane adsorbers with consistent performance. To study the effect of functional-group density, membrane adsorbers from sPEEK with different sulfonation degrees (52%, 62%, and 72%) were fabricated. Despite the increased functional-group density, the dynamic adsorption capacity did not increase accordingly. However, in all presented cases, at least a monolayer coverage was obtained, demonstrating ample functional groups available within the area occupied by a lysozyme molecule. Our study showcases a ready-to-use membrane adsorber for the recovery of positively charged molecules, using lysozyme as a model protein, with potential applications in removing heavy metals, dyes, and pharmaceutical components from process streams. Furthermore, this study highlights factors, such as fiber diameter and functional-group density, for optimizing the membrane adsorber's performance.

Pore-structure control in ultramicroporous porous coordination polymers for efficient selective capture of acetylene

Physical adsorption separation of acetylene (C2H2) from carbon dioxide (CO2) on porous coordination polymers is a promising technique. However, it is still a particular challenge to realize the practical separation application of porous coordination polymers (PCPs) adsorbents with high separation performance, moderate adsorption heat, high stability and low cost. Herein, we demonstrate the efficient adsorption and separation of C2H2/CO2 from aspartate/malate anions columnar PCPs (namely PCPs-asp, PCPs-mal and PCPs-mal-n) exploiting the hydroxyl/amino sites within fine-tuning pore structures. Its one-dimensional (1D) chains and abundant hydroxyl/amino functional sites matched with target molecules, affording these anions columnar PCPs with not only high separation selectivity for C2H2/CO2, but also excellent gas capacity. Among them, PCPs-mal possesses an ultra-high C2H2 storage density of 655 g·L−1 under ambient conditions, and even close to the density of solid C2H2 at 189 K (729 g·L−1). PCPs-mal exhibits an IAST separation selectivity as high as 15.2 for the equimolar C2H2/CO2 binary mixture. The breakthrough experiments demonstrate that PCPs-mal realize efficient binary C2H2/CO2 separation with an acetylene dynamic adsorption capacity of 2.03 mmol·g−1. Theoretical calculations and GCMC simulations further provide critical insight into the separation mechanism at the molecular level. More importantly, the facile scaled synthesis, low adsorption enthalpy, and high separation performance make it cost-effective for real-world applications.

Metal-Organic Frameworks for Breakthrough Separation of 2-Butene Isomers with High Dynamic Selectivity and Capacity.

Developing porous sorbents represents a potential energy-efficient way for industrial gas separation. However, a bottleneck for reducing the energy penalty is the trade-off between dynamic adsorption capacity and selectivity. Herein, we showed this problem can be overcome by modulating the kinetic and thermodynamic separation behaviours in metal-organic frameworks for sieving 2-butene geometric isomers, which are desired for upgrading the raffinates to higher value-added end products. We found that the iron-triazolate framework can realize the selective shape screening of 2-butene isomers assisted by electrostatic interactions at the pore apertures. Further introducing uncoordinated N binding sites by ligand substitution lowered the gas diffusion barrier and greatly boosted the dynamic separation performance. In breakthrough tests under ambient conditions, trans-2-C4 H8 can be efficiently separated from cis-2-C4 H8 with a record capacity of 2.10 mmol g-1 with high dynamic selectivity of 2.39.

Metal‐Organic Frameworks for Breakthrough Separation of 2‐Butene Isomers with High Dynamic Selectivity and Capacity

AbstractDeveloping porous sorbents represents a potential energy‐efficient way for industrial gas separation. However, a bottleneck for reducing the energy penalty is the trade‐off between dynamic adsorption capacity and selectivity. Herein, we showed this problem can be overcome by modulating the kinetic and thermodynamic separation behaviours in metal–organic frameworks for sieving 2‐butene geometric isomers, which are desired for upgrading the raffinates to higher value‐added end products. We found that the iron‐triazolate framework can realize the selective shape screening of 2‐butene isomers assisted by electrostatic interactions at the pore apertures. Further introducing uncoordinated N binding sites by ligand substitution lowered the gas diffusion barrier and greatly boosted the dynamic separation performance. In breakthrough tests under ambient conditions, trans‐2‐C4H8 can be efficiently separated from cis‐2‐C4H8 with a record capacity of 2.10 mmol g−1 with high dynamic selectivity of 2.39.