Atom efficiency in small molecule and macromolecule synthesis: general discussion

A. Buchard, M. North, C. Kozak, E. Remiezowicz, P. Abrantes, A. Bardow, J. Dodson, C. Williams, J. Albo, I. Ingram, G. V. S. M. Carrera, P. Styring, M. Poliakoff, K. Lamb, E. A. Quadrelli, N. MacDowell, G. Dowson, M. Aresta, R. Heyn, J. A. Castro-Osma, W. Webb, R. Silva, A. Marciniak, C. Jones, C. T. Yavuz, C. Capacchione, A. Coogan, M. Priestnall

Faraday Discuss., 183, 97-123, (2015). DOI: 10.1039/C5FD90079D.

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Capture agents, conversion mechanisms, biotransformations and biomimetics: general discussion

E. Remiezowicz, J. Spooren, E. Bay, A. Cowan, I. Ingram, P. Abrantes, M. N. da Ponte, M. North, J. Albo, P. Styring, M. Priestnall, K. Lamb, M. Aresta, E. A. Quadrelli, R. Heyn, A. Bardow, W. Webb, R. Silva, C. Alonso-Moreno, C. Janaky, G. Maitland, S. Vaidyanathan, G. V. S. M. Carrera, D. Reed, K. Vanbroekhoven, C. T. Yavuz, D. Pant, N. Hollingsworth

Faraday Discuss., 183, 463-487, (2015). DOI: 10.1039/C5FD90082D.

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Insights of CO2 Adsorption Performance of Amine Impregnated Mesoporous Silica (SBA-15) at Wide Range Pressure and Temperature Conditions

R. Ullah, M. Atilhan*, A. Canlier, S. Aparicio, C. T. Yavuz*
Int. J. Greenh. Gas Control, 43, 22-32, (2015). DOI: 10.1016/j.ijggc.2015.09.013.

Beside IGCC, efficient storage and transportation of CO₂ and other gases require pressurize conditions. CO₂ and other gases adsorption on solid sorbents at high pressure and various temperatures are extremely important as long as the environmental purification via gas capture and separation and gas transpiration are concern. The main objective of the present research was to investigate the effect of amine impregnation on the CO₂, methane and nitrogen adsorption capacity of mesoporous silica (SBA-15). Ordered mesoporous silica (SBA-15) was prepared and modified with ammonium hydroxide solution to introduce NH₂ functional groups within the pores of materials to produce modified SBA-15 (MSBA-15). The newly prepared materials were characterized with X-ray diffraction analysis, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis were performed to measure pore volume as well as the surface area of both the unmodified and modified samples. Results revealed that the crystal structures of SBA-15 were matched with that of MSBA15; yet, pore volume of the modified material was almost reduced to 50% of the pristine material indicating amine loading into the pore channels. Importantly, gas sorption capacity was investigated at 200 bars and three different temperatures of 318 K, 328 K, and 338 K by using state-of-the-art gravimetric Rubotherm® magnetic suspension sorption apparatus. Gas sorption experiments showed that modified mesoporous silica adsorbed 1.6164 mmol/g of CO₂ at 1 bar which is almost double than that of 0.6462 mmol/g adsorbed by unmodified material. Quantitative selectivity of both the materials varied as CO₂, CH₄ and N₂.

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Systematic Investigation of the Effect of Polymerization Routes on the Gas Sorption Properties of Nanoporous Azobenzene Polymers

O. Buyukcakir, S. H. Je, J. Park, H. A. Patel, Y. Jung, C. T. Yavuz*, A. Coskun*
Chem. Eur. J., 21 (43), 15320–15327, (2015). DOI: 10.1002/chem.201501233.

Functional-group-oriented polymerization strategies have contributed significantly to the initial development of porous polymers and have led to the utilization of several well-known organic transformations in the synthesis of these polymers. Because there are multiple polymerization routes that can be used to introduce the same chemical functionality, it is very important to demonstrate the effect of different polymerization routes on the gas-sorption properties of these chemically similar polymers. Herein, we have studied the rich chemistry of azobenzenes and synthesized four chemically similar nanoporous azobenzene polymers (NABs) with surface areas of up to 1021 m2 g−1. The polymerization routes have a significant impact on the pore-size distributions of the NABs, which directly affects the temperature dependence of the CO₂/N₂ selectivity. A pore-width maximum of 6–8 Å, narrow pore-size distribution, and small particle size (20–30 nm) were very critical for high CO₂/N₂ selectivity and N₂ phobicity, which is associated with azo linkages and realized at warm temperatures. Our findings collectively suggest that an investigation of different polymerization routes for the same chemical functionalization is critical to understand fully the combined effect of textural properties, local environment, and chemical functionalization on the gas-sorption properties of nanoporous polymers.

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Covalent organic polymer framework with C-C bonds as a fluorescent probe for selective iron detection

E. Ozdemir, D. Thirion, C. T. Yavuz*
RSC Adv., 5, 69010-69015, (2015). DOI: 10.1039/C5RA10697D.

A new carbon–carbon bonded nanoporous polymer network was synthesized via efficient and catalyst free Knoevenagel-like condensation polymerization in near quantitative yields. The obtained polymer network, Covalent Organic Polymer – COP-100 possesses strong fluorescent properties and designed solubility in polar aprotic solvents, which shows promise for use as a metal-sensing material in solution. COP-100 exhibited high selectivity towards Fe2+ and Fe3+ in the presence of other common metal cations (Al3+, Ag+, Cd2+, Co2+, Cr3+, Cu2+, Hg2+, Mg2+, Mn2+, Na+, Ni2+, Zn2+) as the fluorescence of the polymer was significantly quenched even at very low concentrations. In the range from 2.5 × 10−6 to 2 × 10−4 M, a linear fluorescence emission response with equipment limited detection minimum of 2.13 × 10−7 M and 2.45 × 10−7 M for Fe2+ and Fe3+, respectively, was observed. These results suggest that COP-100 is a promising material as a selective fluorescence sensor for iron ions.

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Highly Optimized CO2 Capture by Inexpensive Nanoporous Covalent Organic Polymers and Their Amine Composites

H. A. Patel, C. T. Yavuz*
Faraday Discuss., 183, 401-412, (2015). DOI: 10.1039/C5FD00099H.

Carbon dioxide (CO₂) storage and utilization requires effective capture strategies that limit energy penalties. Polyethylenimine (PEI)-impregnated covalent organic polymers (COPs) with a high CO₂ adsorption capacity are successfully prepared in this study. A low cost COP with a high specific surface area is suitable for PEI loading to achieve high CO₂ adsorption, and the optimal PEI loading is 36 wt%. Though the adsorbed amount of CO₂ on amine impregnated COPs slightly decreased with increasing adsorption temperature, CO₂/N₂ selectivity is significantly improved at higher temperatures. The adsorption of CO₂ on the sorbent is very fast, and a sorption equilibrium (10% wt) was achieved within 5 min at 313 K under the flow of simulated flue gas streams. The CO₂ capture efficiency of this sorbent is not affected under repetitive adsorption–desorption cycles. The highest CO₂ capture capacity of 75 mg g−1 at 0.15 bar is achieved under dry CO₂ capture however it is enhanced to 100 mg g−1 in the mixed gas flow containing humid 15% CO₂. Sorbents were found to be thermally stable up to at least 200 °C. TGA and FTIR studies confirmed the loading of PEIs on COPs. This sorbent with high and fast CO₂ sorption exhibits a very promising application in direct CO₂ capture from flue gas.

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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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Influence of interlayer functionalization of kaolinite on property profile of copolymer nanocomposites

S. Zulfiqar*, M. I. Sarwar*, N. Rasheed, C. T. Yavuz
Appl. Clay Sci., 112–113, 25–31, (2015). DOI: 10.1016/j.clay.2015.04.010.

Nanocomposites of co-poly (vinyl chloride–polyvinyl acetate–polyvinyl alcohol) (PVC–PVAc–PVA) and kaolinite were prepared via solution intercalation technique. To improve compatibility among the phases and to expand the interlayer basal spacing, kaolinite was modified using dimethylsulfoxide (DMSO) as a swelling agent. The influence of kaolinite dispersion and interaction between the disparate phases on the properties of nanocomposites were investigated using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, thermogravimetric analysis (TGA) and water absorption measurements. IR data confirmed the hydrogen bonds formed between DMSO and the surface hydroxyl groups of kaolinite. XRD and microscopic results revealed that clay mineral was intercalated with uniform dispersion at nanoscale in the matrix. Tensile testing of these materials indicated significant improvements in the mechanical properties relative to the pure copolymer. Incorporation of kaolinite into the organic phase enhanced the thermal stability of the nanocomposites. Water absorption of the nanomaterials was reduced upon the addition of modified kaolinite rendering decreased permeability with increasing dispersibility of clay mineral in the copolymer matrix.

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A Half Millimeter Thick Coplanar Flexible Battery with Wireless Recharging Capability

J. S. Kim, D. Ko, D. J. Yoo, D. S. Jung, C. T. Yavuz, N. I. Kim, I. S. Choi, J. Y. Song*, J. W. Choi*
Nano Lett., 15 (4), 2350–2357, (2015). DOI: 10.1021/nl5045814.
Most read paper in March 2015.

Most of the existing flexible lithium ion batteries (LIBs) adopt the conventional cofacial cell configuration where anode, separator, and cathode are sequentially stacked and so have difficulty in the integration with emerging thin LIB applications, such as smart cards and medical patches. In order to overcome this shortcoming, herein, we report a coplanar cell structure in which anodes and cathodes are interdigitatedly positioned on the same plane. The coplanar electrode design brings advantages of enhanced bending tolerance and capability of increasing the cell voltage by in series-connection of multiple single-cells in addition to its suitability for the thickness reduction. On the basis of these structural benefits, we develop a coplanar flexible LIB that delivers 7.4 V with an entire cell thickness below 0.5 mm while preserving stable electrochemical performance throughout 5000 (un)bending cycles (bending radius = 5 mm). Also, even the pouch case serves as barriers between anodes and cathodes to prevent Li dendrite growth and short-circuit formation while saving the thickness. Furthermore, for convenient practical use wireless charging via inductive electromagnetic energy transfer and solar cell integration is demonstrated.

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Synthesis of a nanoporous 1,2,4-oxadiazole network with high CO2 capture capacity

D. Ko, H. A. Patel, C. T. Yavuz*
Chem. Commun., 51, 2915-2917 (2015). [DOI]

Developing an adsorbent to mitigate carbon dioxide without large energy penalty is highly desired. Here, we present a silylation synthetic route to form a processable and otherwise impossible porous 1,2,4-oxadiazole network, which achieves 2 mmol/g of CO2 capacity owing to nitrogen-rich structure. This network shows high CO2/N2-selectivity, thermal stability up to 450 oC, and low-heat of adsorption (26.4 kJ/mol), facilitating easy regeneration.

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A Novel, Reactive Green Iron Sulfide (Sulfide Green Rust) Formed on Iron Oxide Nanocrystals

C. Jones, S. Chattopadhyay, N. I. Gonzalez-Pech, C. Avendano, N. Hwang, S. S. Lee, M. Cho, A. Ozarowski, A. Prakash, J. T. Mayo, C. T. Yavuz, V. L. Colvin*
Chem. Mater., 27 (3), 700-707 (2015). DOI: 10.1021/cm5028942.

Iron oxide nanocrystals are of great scientific and technological interest. In this work, these materials are the starting point for producing a reactive nanoparticle whose surface resembles that of natural green rusts. Treatment of iron oxide nanoparticles with cysteamine leads to the reduction of iron and the formation of a brilliant green aqueous solution of nanocrystals rich in iron(II). These materials remained crystalline with magnetic and structural features of the original iron oxide. However, new low-angle X-ray diffraction peaks as well as vibrational features characteristic of cysteamine were found in the nanocrystalline product. X-ray absorption spectroscopy (XAS), X-ray photoemission (XPS) and Mössbauer spectroscopies indicated the presence of an iron(II)-rich phase with high sulfur content analogous to the iron–oxygen structures found in natural green rusts. Electron microscopy found that these structural components remained associated with the nonreduced iron oxide cores. These sulfur-rich analogs of natural green rusts are highly reactive and were able to rapidly degrade a model organic dye in water. This observation suggests possible actuation with a cysteamine treatment of inert and magnetic iron oxide particles at the point-of-use for environmental remediation.

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