High-capacity methane storage in flexible alkane-linked porous aromatic network polymers

V. Rozyyev, D. Thirion, R. Ullah, J. Lee, M. Jung, H. Oh, M. Atilhan*, C. T. Yavuz*
Nat. Energy, 4, 604-611, (2019).
DOI: 10.1038/s41560-019-0427-x
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Adsorbed natural gas (ANG) technology is a viable alternative to conventional liquefied or compressed natural-gas storage. Many different porous materials have been considered for adsorptive, reversible methane storage, but fall short of the US Department of Energy targets (0.5 g g−1, 263 l l−1). Here we prepare a flexible porous polymer, made from benzene and 1,2-dichloroethane in kilogram batches, that has a high methane working capacity of 0.625 g g−1 and 294 l l−1 when cycled between 5 and 100 bar pressure. We suggest that the flexibility provides rapid desorption and thermal management, while the hydrophobicity and the nature of the covalently bonded framework allow the material to tolerate harsh conditions. The polymer also shows an adsorbate memory effect, where a less adsorptive gas (N2) follows the isotherm profile of a high-capacity adsorbate (CO2), which is attributed to the thermal expansion caused by the adsorption enthalpy. The high methane capacity and memory effect make flexible porous polymers promising candidates for ANG technology.

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Selective removal of heavy metal ions by disulfide linked polymer networks

D. Ko, J. S. Lee, H. A. Patel, M. H. Jakobsen, Y. Hwang, C. T. Yavuz, H. C. B. Hansen, H. R. Andersen*
J. Hazard. Mater., 332, 140–148, (2017).
DOI: 10.1016/j.jhazmat.2017.03.007.

Heavy metal contaminated surface water is one of the oldest pollution problems, which is critical to ecosystems and human health. We devised disulfide linked polymer networks and employed as a sorbent for removing heavy metal ions from contaminated water. Although the polymer network material has a moderate surface area, it demonstrated cadmium removal efficiency equivalent to highly porous activated carbon while it showed 16 times faster sorption kinetics compared to activated carbon, owing to the high affinity of cadmium towards disulfide and thiol functionality in the polymer network. The metal sorption mechanism on polymer network was studied by sorption kinetics, effect of pH, and metal complexation. We observed that the metal ions–copper, cadmium, and zinc showed high binding affinity in polymer network, even in the presence of competing cations like calcium in water.

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Enhanced sorption cycle stability and kinetics of CO2 on lithium silicates using lithium ion channeling effect of TiO2 nanotubes

J. S. Lee, C. T. Yavuz*
Ind. Eng. Chem. Res., accepted.
DOI: 10.1021/acs.iecr.6b04918.

Lithium silicate (Li₄SiO₄) is a promising high temperature CO₂ sorbent because of its large CO₂ capacity at elevated temperatures with low materials cost. However, the conventional nonporous Li₄SiO₄ shows very poor CO₂ adsorption kinetics. Thus, a Li₄SiO₄–TiO₂ nanotubes complex was synthesized where LiOH and fumed silica would be calcined around TiO₂ nanotubes. TiO₂ nanotubes in Li4SiO4 structure functioning as open highways, lithium ions were able to channel through the bulky structure and enhance the sorption kinetics, leading the total adsorption capacity to near theoretical values. Furthermore, cyclic studies at 700 °C revealed strong stability over at least 10 cycles. These findings indicate that stability and kinetics of CO₂ sorption can be greatly improved by the nanotube composites of known adsorbents.

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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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