Processing nanoporous organic polymers in liquid amines

J. Byun*, D. Thirion, C. T. Yavuz

Beilstein J. Nanotech., 10, 1844–1850 (2019). Open Access 
DOI: 10.3762/bjnano.10.179

Rigid network structures of nanoporous organic polymers provide high porosity, which is beneficial for applications such as gas sorption, gas separation, heterogeneous (photo)catalysis, sensing, and (opto)electronics. However, the network structures are practically insoluble. Thus, the processing of nanoporous polymers into nanoparticles or films remains challenging. Herein, we report that nanoporous polymers made via a Knoevenagel-like condensation can be easily processed into nanoparticles (115.7 ± 40.8 nm) or a flawless film by using liquid amines as a solvent at elevated temperatures. FTIR spectra revealed that the carboxyl groups in the nanoporous polymers act as reactive sites for amines, forming new functionalities and spacing the polymeric chains to be dissolved in the liquid amines. The processed film was found to be CO2-philic despite the low surface area, and further able to be transformed into a fine carbon film by thermal treatment.

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Reversible water capture by a charged metal-free porous polymer

J. Byun, H. A. Patel, D. Thirion, C. T. Yavuz*
Polymer, 126, 308-313, (2017).
Invited paper for the special issue on Porous Polymers
DOI: 10.1016/j.polymer.2017.05.071

Climate change and industrial pollution threatens the availability of clean water. Although established protocols of water treatment exist, water capture by porous materials has emerged as a viable alternative to energy intensive processes. Here we introduce a new charged porous polymer that is capable of capturing and releasing water by simple humidity or temperature swings. The quaternary amines on the framework structure attract water molecules and further solvate by coordination. The porosity of the network structure also provides enough void where water can diffuse throughout the solid. Water uptake capacity of the porous polymer surpasses common desiccants like silica gel and molecular sieves, and has the potential to act as an organic desiccant in applications like electronics or food packaging.

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Carbon Dioxide Capture Adsorbents: Chemistry and Methods, A Tutorial Review

H. A. Patel, J. Byun, C. T. Yavuz*
ChemSusChem, 10, 7, 1303-1317, (2017). DOI: 10.1002/cssc.201601545.
View PDF here

Graphical Art by Ella Marushchenko.

Excess carbon dioxide (CO₂) emissions and the inevitable consequences continuing to stimulate hard debate and awareness in both academic and public spaces, despite the clutter on understanding what really is needed to capture and store the unwanted CO₂. Capture is the most costly, nearly 70 % of the price tag on the entire carbon capture and storage (CCS) operation. In this tutorial review, we describe and evaluate CO₂ capture science and technology based on adsorbents in the context of chemistry and methods, after briefly introducing current status of CO₂ emissions. An effective sorbent design is suggested, where six checkpoints are expected to be met: cost, capacity, selectivity, stability, recyclability and fast kinetics.

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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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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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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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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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Nanoporous Networks as Caging Supports for Uniform, Surfactant-free Co3O4 Nanocrystals and Their Applications in Energy Storage and Conversion

J. Byun, H. A. Patel, D. J. Kim, C. H. Jung, J. Y. Park*, J. W. Choi*, C. T. Yavuz* 
J. Mater. Chem. A, 3, 15489 - 15497, (2015). DOI: 10.1039/C5TA02825F.
Selected among "Hot Papers of 2015"

We report a new, surfactant-free method to produce Co₃O₄ nanocrystals with controlled sizes and high dispersity by caging templation of nanoporous networks. The morphologies of Co₃O₄ nanoparticles differ from wires to particulates by simply varying solvents. The composites of nanoparticles within network polymers are highly porous and are promising for many applications where accessible surface and aggregation prevention are important. The electrochemical performance of the composites demonstrates superior capacity and cyclic stability at a high current density (∼980 mA h g−1 at the 60th cycle at a current density of 1000 mA g−1). In a catalytic oxidation reaction of carbon monoxide, the composites exhibit a remarkable stability (in excess of 35 hours) and catalytic performance (T100 = 100 °C).

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Magnetic BaFe12O19 nanofiber filter for effective separation of Fe3O4 nanoparticles and removal of arsenic

J. Byun, H. A. Patel, C. T. Yavuz*
J. Nanopart. Res., 16:2787 (2014). [DOI]

Magnetic nanoparticles are promising in applications where magnetic separation is intended, although material losses via leaching mechanisms are often inevitable. Magnetic separations with widely available permanent magnets can effectively trap particles, leading to a complete removal of used or waste particles. In this report, we first demonstrate the synthesis of the thinnest (112.7 ± 16.4 nm) and most magnetic (71.96 emu g−1) barium hexaferrite (BaFe₁₂O₁₉, BHF—fridge magnet) via an organic solvent-free electrospinning procedure. When the fibers are then packed into a column, they clearly remove 12 nm magnetite (Fe₃O₄) nanoparticles quantitatively. The same BHF cartridge also removes more than 99.9 % As-treated magnetite nanoparticles at capacities up to 70 times of its weight. As a result, one liter of 150 μg L−1 As-contaminated water can be purified rapidly at a material cost of less than 2 US cents.

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Nanoporous covalent organic polymers incorporating Tröger’s base functionalities for enhanced CO2 capture

J. Byun, S. H. Je, H. A. Patel, A. Coskun,* C. T. Yavuz*
J. Mater. Chem. A, 2, 12507-12512, 2014. [DOI] [pdf] [WoS]

The CO₂ uptake capacity and CO₂/N₂ selectivity of Tröger’s base–bridged nanoporous covalent organic polymers (TB-COPs) were investigated. TB-COPs were synthesized by reacting amine terminals of tetrahedral monomers - namely, tetraanilyladamantane and tetraanilylmethane - with dimethoxymethane in a one–pot reaction under relatively mild conditions. Interestingly, these two tetrahedral monomers formed nanoporous polymers with substantially different surface areas. While the trögerization of tetraanilyladamantane monomer (TB-COP-1) exhibit high surface area of 1340 m2 g-1, that of tetraanilylmethane monomer (TB-COP-2) is found to be only 0.094 m2 g-1. This unusual phenomenon can be explained by the proximity of amino moieties to each other within the monomeric unit. Shorter distance between the amino groups enables intramolecular cyclization along with the intermolecular one, thus resulting in much lower porosity. TB-COP-1 exhibits significant CO2 uptakes up to 5.19 and 3.16 mmol g-1 at 273 and 298K under ambient pressure, and CO₂/N₂ selectivities of 79.2 and 68.9 at 273 and 298K at 1 bar for the gas mixture of CO₂:N₂ in the ratio of 0.15:0.85. It is noteworthy that TB-COP-1 showed remarkable selectivity retention with rising temperature from 273 to 298 K.

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Highly Stable Nanoporous Sulfur bridged Covalent Organic Polymers for Carbon Dioxide Removal

H. A. Patel, F. Karadas, J. Byun, J. Park, E. Deniz, A. Canlier, Y. Jung,* M. Atilhan*, C. T. Yavuz*
Adv. Funct. Mater., 23, 2270–2276 (2013). [DOI] [pdf]

Carbon dioxide capture and separation requires robust solids that can stand harsh environments where a hot mixture of gases is often found. Herein, the first and comprehensive syntheses of porous sulfur-bridged covalent organic polymers (COPs) and their application for carbon dioxide capture in warm conditions and a wide range of pressures (0–200 bar) are reported. These COPs can store up to 3294 mg g−1 of carbon dioxide at 318 K and 200 bar while being highly stable against heating up to 400 °C. The carbon dioxide capacity of the COPs is also not hindered upon boiling in water for at least one week. Physisorptive binding is prevalent with isosteric heat of adsorptions around 24 kJ mol−1. M06–2X and RIMP2 calculations yield the same relative trend of binding energies, where, interestingly, the dimer of triazine and benzene play a cooperative role for a stronger binding of CO₂ (19.2 kJ mol−1) as compared to a separate binding with triazine (13.3 kJ mol−1) or benzene (11.8 kJ mol−1).

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Arsenic removal by magnetic nanocrystalline barium hexaferrite

H. A. Patel, J. Byun, C. T. Yavuz*
J. Nanopart. Res., 14 (7), 881 (2012). [DOI] [pdf]

Nanoscale magnetite (Fe₃O₄) (15 nm) is known to remove arsenic efficiently but is very difficult to separate or require high magnetic fields to separate out from the waste water after treatment. Anisotropic hexagonal ferrite (BaFe₁₂O₁₉, BHF) is a well-known permanent magnet (i.e., fridge magnets) and attractive due to its low cost in making large quantities. BHF offers a viable alternative to magnetite nanocrystals for arsenic removal since it features surfaces similar to iron oxides but with much enhanced magnetism. Herein, we employ BHF nanocrystalline materials for the first time in arsenic removal from wastewater. Our results show better (75 %) arsenic removal than magnetite of the similar sizes. The BHF nanoparticles, 6.06 ± 0.52 nm synthesized by thermolysis method at 320 °C do not show hexagonal phase, however, subsequent annealing at 750 °C produced pure hexagonal BHF in 200 nm assemblies. By using BHF, we demonstrate that nanoparticle removal is more efficient and fixed bed type cartridge applications are more possible.

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