Charge-specific size-dependent separation of water-soluble organic molecules by fluorinated nanoporous networks

J. Byun, H. A. Patel, D. Thirion, C. T. Yavuz*
Nature Commun., 7, 13377, (2016). OpenAccess
DOI: 10.1038/ncomms13377. ReadCube: rdcu.be/mw1d.
Highlighted in Chemical & Engineering News by Stephen K. Ritter

Molecular architecture in nanoscale spaces can lead to selective chemical interactions and separation of species with similar sizes and functionality. Substrate specific sorbent chemistry is well known through highly crystalline ordered structures such as zeolites, metal organic frameworks and widely available nanoporous carbons. Size and charge-dependent separation of aqueous molecular contaminants, on the contrary, have not been adequately developed. Here we report a charge-specific size-dependent separation of water-soluble molecules through an ultra-microporous polymeric network that features fluorines as the predominant surface functional groups. Treatment of similarly sized organic molecules with and without charges shows that fluorine interacts with charges favourably. Control experiments using similarly constructed frameworks with or without fluorines verify the fluorine-cation interactions. Lack of a σ-hole for fluorine atoms is suggested to be responsible for this distinct property, and future applications of this discovery, such as desalination and mixed matrix membranes, may be expected to follow.

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Robust C–C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas

D. Thirion, J. S. Lee, E. Ozdemir, C. T. Yavuz*
Beilstein J. Org. Chem., 12, 2274-2279, (2016). OpenAccess
Invited Paper for the thematic issue on "Organic Porous Materials". DOI: 10.3762/bjoc.12.220.

Effective carbon dioxide (CO₂) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein, we report two new carbon–carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile–aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m2/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified COP-156-amine showed fast and increased CO₂ uptake under simulated moist flue gas conditions compared to the starting network and usual industrial CO₂ solvents, reaching up to 7.8 wt % uptake at 40 °C.

Keywords: C–C bond; CO₂ capture; microporous materials; porous polymers; postmodification

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Engineered nanoparticles for water treatment application

J. Byun, C. T. Yavuz*
Chapter 2 in Engineered Nanoparticles and the Environment: Biophysicochemical Processes and Toxicity, Edited by B. Xing, C. D. Vecitis, N. Senesi.
WILEY-IUPAC Series in Biophysico-Chemical Processes in Environmental Systems
Published by John Wiley & Sons, Inc.
ISBN: 9781119275824
DOI: 10.1002/9781119275855.ch2

In this chapter, water treatment processes using nanoparticles and studies related to the removal of waterborne contaminants, such as anionic, cationic, and organic pollutants, will be reviewed.

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Synthesis and Easy Functionalization of Highly Porous Networks through Exchangeable Fluorines for Target Specific Applications

D. Thirion, Y. Kwon, V. Rozyyev, J. Byun, C. T. Yavuz*
Chem. Mater., 28 (16), 5592–5595, (2016). DOI: 10.1021/acs.chemmater.6b02152.

Porous materials as adsorbents with high affinities to target molecules have great potential to facilitate environmentally important separations and remediation. One key challenge is to keep a reactive functionality inert while building a super structure. Protection or post-modification methods are limited because of the incomplete activation, and often require harsh conditions that also compromise the framework integrity. Here, a metal-free, one-pot, RT, deprotection-coupling, regioselective reaction is used for the first time to synthesize a porous network with high specific surface area (1035 m2/g) and easy post-functionalization. The obtained microporous polymer is a robust C-C bonded structure with alkyne and perfluorinated moieties. Aromatic fluorines readily undergo nucleophilic substitutions facilitating numerous post-modification possibilities, a particular feature that was not previously available.

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Investigation of Ester- and Amide-Linker-Based Porous Organic Polymers for Carbon Dioxide Capture and Separation at Wide Temperatures and Pressures

R. Ullah§, M. Atilhan*, B. Anaya, S. Al-Muhtaseb, S. Aparicio, H. A. Patel§, D. Thirion, C. T. Yavuz*
ACS Appl. Mater. Interfaces , 8 (32), 20772–20785, (2016). §: Equal contribution. DOI: 10.1021/acsami.6b05927.

Organic compounds, such as covalent organic framework, metal–organic frameworks, and covalent organic polymers have been under investigation to replace the well-known amine-based solvent sorption technology of CO2 and introduce the most efficient and economical material for CO2 capture and storage. Various organic polymers having different function groups have been under investigation both for low and high pressure CO2 capture. However, search for a promising material to overcome the issues of lower selectivity, less capturing capacity, lower mass transfer coefficient and instability in materials performance at high pressure and various temperatures is still ongoing process. Herein, we report synthesis of six covalent organic polymers (COPs) and their CO2, N2, and CH4 adsorption performances at low and high pressures up to 200 bar. All the presented COPs materials were characterized by using elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. Physical properties of the materials such as surface areas, pore volume and pore size were determined through BET analysis at 77 K. All the materials were tested for CO2, CH4, and N2 adsorption using state of the art equipment, magnetic suspension balance (MSB). Results indicated that, amide based material i.e. COP-33 has the largest pore volume of 0.2 cm2/g which can capture up to the maximum of 1.44 mmol/g CO2 at room temperature and at pressure of 10 bar. However, at higher pressure of 200 bar and 308 K ester-based compound, that is, COP-35 adsorb as large as 144 mmol/g, which is the largest gas capturing capacity of any COPs material obtained so far. Importantly, single gas measurement based selectivity of COP-33 was comparatively better than all other COPs materials at all condition. Nevertheless, overall performance of COP-35 rate of adsorption and heat of adsorption has indicated that this material can be considered for further exploration as efficient and cheaply available solid sorbent material for CO2 capture and separation.

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High performance CO2 filtration and sequestration by using bromomethyl benzene linked microporous networks

R. Ullah§, M. Atilhan*, B. Anaya, S. Al-Muhtaseb, S. Aparicio, D. Thirion§, C. T. Yavuz* 
RSC Adv. , 6, 66324–66335, (2016). §: Equal contribution. DOI: 10.1039/C6RA13655A

Porous solid sorbents have been investigated for the last few decades to replace the costly amine solution and explore the most efficient and economical material for CO₂ capture and storage. Covalent organic polymers (COPs) have been recently introduced as promising materials to overcome several issues associated with the solid sorbents such as thermal stability and low gas capturing capacity. Herein we report the synthesis of four COPs and their CO₂, N₂ and CH₄ uptakes. All the presented COP materials were characterized by using an elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. The physical properties of the materials such as surface area, pore volume and pore size were determined by BET analysis at 77 K. All the materials were tested for CO₂, CH₄ and N₂ adsorption through a volumetric method using magnetic sorption apparatus (MSA). Among the presented materials, COP-118 has the highest surface area of 473 m² g^-1 among the other four materials and has shown excellent performance by capturing 2.72 mmol g^-1 of CO₂, 1.002 mmol g^-1 of CH₄ and only 0.56 mmol g^-1 of N₂ at 298 K and 10 bars. However the selectivity of another material, COP-117-A, was better than that of COP-118. Nevertheless, the overall performance of the latter has indicated that this material can be considered for further exploration as an efficient and cheaply available solid sorbent compound for CO₂ capture and separation.

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High-Pressure Methane, Carbon Dioxide, and Nitrogen Adsorption on Amine-Impregnated Porous Montmorillonite Nanoclays

M. Atilhan*, S. Atilhan§, R. Ullah§, B. Anayeha, T. Cagin, C. T. Yavuz, S. Aparicio*
J. Chem. Eng. Data , 61 (8), 2749–2760, (2016). §: Equal contribution. DOI: 10.1021/acs.jced.6b00134

Montmorillonite nanoclay was studied for its capability of storing carbon dioxide, methane, and nitrogen at elevated pressures. Adsorption data were collected to study and assess the possible applications of montmorillonite to gas storage, as it is available in depleted shale reservoirs. The thermodynamic properties of montmorillonite and its amine impregnated structures were studied in this manuscript. Material characterization via Brunauer–Emmett–Teller analysis, thermogravimetric analysis, Fourier transform infrared and energy dispersive X-ray spectroscopies, and scanning electron microscopy was carried out on the nanoclay samples followed by low- and high-pressure gas sorption experimental measurements via high-pressure magnetic suspension sorption apparatus at 298 and 323 K isotherms up to 50 bar. Selectivities of each gas on each nanoclay material is calculated based on single gas adsorption measurements and presented in the manuscript. Additionally, heat of adsorption and kinetics of adsorption are calculated and reported.

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Observation of wrapping mechanism in amine carbon dioxide molecular interactions on heterogeneous sorbents

D. Thirion, V. Rozyyev, J. Park, Y. Jung, M. Atilhan, C. T. Yavuz*
Phys. Chem. Chem. Phys., 18, 14177-14181, (2016). DOI: 10.1039/C6CP01382A

Liquid, solvated amine based carbon capture is the core of all commercial or planned CO2 capture operations. Despite the intense research, few have looked systematically into the nature of amine molecules and their CO2 interaction. Here, we report a systematic introduction of linear ethylene amines on the walls of highly porous Davankov type network structures through simple bromination intermediates. Surprisingly, isosteric heats of CO2 adsorption show a clear linear trend with the increase in the length of the tethered amine pendant groups, leading to a concerted cooperative binding with additional H-bonding contributions from the unassociated secondary amines. CO2 uptake capacities multiply with the nitrogen content, up to an unprecedented four to eight times of the starting porous network under flue gas conditions. The reported procedure can be generalized to all porous media with the robust hydrocarbon framework in order to convert them into effective CO2 capture adsorbents.

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Rapid extraction of Uranium ions from seawater using novel porous polymeric adsorbents

Y. Sihn,§ J. Byun,§ H. A. Patel, W. Lee*, C. T. Yavuz*
RSC Adv., 6, 45968-45976, (2016). §: Equal contribution. DOI: 10.1039/C6RA06807C

Seawater contains uranium in surprisingly high quantities that can supply vast energy, if recovered economically. Attempts to design effective sorbents led to the identification of organic functional groups such as amidoximes. Here we report a porous polymer, a polymer of intrinsic microporosity (PIM) with permanent pores that feature amidoxime pendant groups, which is capable of removing more than 90% uranyl [U(VI)] from seawater collected from the Ulleung basin of the East Sea of the Republic of Korea. From this uptake, over 75% was collected in less than six hours, leading to highly feasible field applications. When the seawater was acidified by bubbling CO2 (pH = 5.4), the uptake increased dramatically. Regeneration studies showed full recovery of sorbents and no loss in capture capacity. Our results indicate that successful uranium recovery can be realized by scalable applications of porous polymeric networks and when low cost CO2 is co-administered, uptake can be significantly enhanced.

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Increasing mesoporosity by a silica hard template in a covalent organic polymer for enhanced amine loading and CO2 capture capacity

H. Lee, C. T. Yavuz*
Micropor. Mesopor. Mat., 229, 44-50 (2016). DOI: 10.1016/j.micromeso.2016.04.019.

Solid sorbents for chemisorptive carbon dioxide uptake in post-combustion scenarios require strong binding groups like amines. Post-synthetic impregnation of reactive amines requires large pore volumes. Covalent organic polymers (COPs) are microporous (or narrow mesoporosity) network polymers with physisorptive behavior. Herein as the first of such attempt in porous organic polymers, we modified COP-1, which is an inexpensive, scalable porous polymer for effective amine loading. By expanding the pore of COP-1 through hard templation by silica, the surface area and pore volume are increased by 2.3 and 2.9 times, respectively. It was shown that the increase of pore volume was mostly from pores larger than 5 nm and it correlates well with the silica particle size (12 nm) and the inter-particle pore sizes of silica (31 nm). As a result, amine impregnated Si-COP-1 adsorbs CO₂ with the increase of 2.44 at 273 K and 4.06 times at 298 K (at flue gas relevant partial pressure of 0.15 bar) over the parent COP-1. Our results show the possibility of tuning porosity for developing industrially feasible CO₂ capturing sorbents.

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Crosslinked “poisonous” polymer: Thermochemically stable catalyst support for tuning chemoselectivity

S. Yun, S. Lee, S. Yook, H. A. Patel, C. T. Yavuz, M. Choi*
ACS Catalysis, 6, 2435-2442 (2016). DOI: 10.1021/acscatal.5b02613.

Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are “transient” selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a “permanent” selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a “molecular gate” that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2–D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.

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Synthesis, characterization and evaluation of porous polybenzimidazole materials for CO2 adsorption at high pressures

R. Ullah, M. Atilhan*, A. Diab, E. Deniz, S. Aparicio*, C. T. Yavuz*
Adsorption, 22 (2), 247-260 (2016). DOI: 10.1007/s10450-016-9762-4.

Porous polybenzimidazole polymers have been under investigation for high and low pressure CO2 adsorption due to the well-built stability under high pressure and at various temperatures. Pressure swing and temperature swing processes like integrated gasification combined cycle require materials which can operate efficiently at high pressure and high temperature and can remove CO2. In this manuscript we report synthesis, characterization and evaluation of two polybenzimidazole materials (PBI-1 and PBI-2), which were prepared with two different solvents and different cross-linking agents by condensation techniques. Low and high pressure CO2 sorption characteristic of both the materials were evaluated at 273 and 298 K. Thermal gravimetric analysis showed high temperature stability up to 500 °C for the studied materials. PBI-1 has shown very good performance by adsorbing 3 times more (1.8025 mmolg−1 of CO2) than PBI-2 at 0 °C and at low pressures. Despite low surface area results obtained via BET techniques, at 50 bars PBI-1 adsorbed up to 6.08 mmolg−1 of CO2. Studied materials have shown flexible behavior under applied pressure that leads to so-called “gate-opening” adsorption behavior and it makes these materials promising adsorbents of CO2 at high pressures and it is discussed in the manuscript in detail.

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Nanoporous networks as effective stabilisation matrixes for nanoscale zero valent iron and groundwater pollutant removal

P. D. Mines, J. Byun, Y. Hwang, H. A. Patel, H. R. Andersen, C. T. Yavuz*
J. Mater. Chem. A, 4, 632-639 (2016). DOI: 10.1039/C5TA05025A.

Nanoscale zero-valent iron (nZVI), with its reductive potentials and wide availability, offers degradative remediation of environmental contaminants. Rapid aggregation and deactivation hinder its application in real-life conditions. Here, we show that by caging nZVI into the micropores of porous networks, in particular Covalent Organic Polymers (COPs), we dramatically improved its stability and adsorption capacity, while still maintaining its reactivity. We probed the nZVI activity by monitoring azo bond reduction and Fenton type degradation of the naphthol blue black azo dye. We found that depending on the wettability of the host COP, the adsorption kinetics and dye degradation capacities changed. The hierarchical porous network of the COP structures enhanced the transport by temporarily holding azo dyes giving enough time and contact for the nZVI to act to break them. nZVI was also found to be more protected from the oxidative conditions since access is gated by the pore openings of COPs.

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