In this manuscript, we report synthesis, characterization and application of amine and amide type covalent organic frameworks as CO2 adsorbent materials at various isotherms and wide pressure conditions. Furthermore, we also report a detailed density functional theory investigation of the studied adsorbents in order to explain their adsorption behaviors and provide comparisons with experimental results. The objective of this work was to investigate custom design porous polymers by building amine and amide functionalities in the final structures, whether they have efficient CO2 capturing performances at wide process conditions that covers both low and high pressure end applications to cover either pre- or post-combustion processes. On the other hand, energy storage performances of these materials were tested by performing H2 sorption experiments as well. Two porous polymers, namely COP-9 and COP-10, were characterized with BET, TGA and FTIR to evaluate the physical properties of studied porous polymers and then were tested for CO2, N2 and H2 adsorption both at low and high pressures. Studied materials were found to have compelling adsorption capacity mostly at high pressures and have very good selectivity for CO2/N2 and CO2/H2 respectively.
Structural Elucidation of Covalent Organic Polymers (COP) and Their Linker Effect on Gas Adsorption Performance via Density Functional Theory Approach
Investigation of the binding affinity gases on porous adsorbents are important for establishing understanding of effective carbon dioxide adsorption and design target specific sorbents for capturing hazardous gases for environmental protection and fuel upgrading. A Density Functional Theory (DFT) study that highlights the impact of covalent organic polymer (COP) design has been conducted to explain the molecular and electronic structure, investigate the interaction sites and elucidate the experimental findings on carbon dioxide (CO2) and nitrogen (N2) sorption on these porous structures. DFT calculations were used to infer the details of the type and the strength of the polymer – gas interaction modes at various interaction sites as well as to quantify short-range interactions between the polymer – gas via topological characteristics analysis of intermolecular forces. Results obtained in this study were used to shed light on CO2 and N2 affinity of the studied polymer structures; interpretations regarding to the macroscopic behaviors were discussed and conclusions were at
Applicability of disulfide-polymer particles surface embedded on alginate beads for cadmium removal from airport derived stormwater
D. Ko, H. Kim, H. Lee, C. T. Yavuz, H. R. Andersen, Y. Hwang
Stormwater runoff derived from airports causes severe cadmium contamination in excess of the maximum limit level and is difficult to treat due to the irregular contamination levels from scattered rainfall. To overcome this and remove cadmium from runoff, a new reactive filtration column is introduced. Sulfur functionalized polymer particles were successfully embedded onto the surface of alginate bead (DiS-algi) and simulated a real stormwater treatment filtration column. The DiS-algi shows 22.3 mg/g of batch and 877 μg/g of continuous flow sorption capacity. Also, the results for the new sorption material show that within 6 mins half of the cadmium was removed with 31 L/mg of Langmuir sorption affinity, outperforming an activated carbon filter. From a breakthrough test the reactive column shows complete uptake of cadmium from a contaminated flow, lasting two hours until reaching the breakthrough point. Furthermore, regeneration tests of the column verified its reusability. DiS-algi appears to be a viable new cadmium sorption mate
Disulfide polymer grafted porous carbon composites for heavy metal removal from stormwater runoff
D. Ko, P. D. Mines, M. H. Jakobsen, C. T. Yavuz, H. C. B. Hansen, H. R. Andersen
The emerging concern of heavy metal pollution derived from stormwater runoff has triggered a demand for effective heavy metal sorbents. To be an effective sorbent, high affinity along with rapid sorption kinetics for environmental relevant concentrations of heavy metals is important. Herein, we have introduced a new composite suitable for trace metal concentration removal, which consists of cheap and common granular activated carbon covered with polymers containing soft bases, thiols, through acyl chlorination (DiS-AC). Material characterization demonstrated that the polymer was successfully grafted and grown onto the surface of the carbon substrate. The distribution coefficient for Cd2+ bonding was 89·103 L/kg at a solution concentration of 0.35 mg/L, which is notably higher than sorption affinities for Cd2+ seen in conventional sorbents. The sorption isotherm is well described by the Freundlich isotherm and within an hour, half of the initial trace (0.2 mg/L) concentration of Cd2+ was removed by the DiS-AC at a sorbent loading of 2 g/L. Therefore, the novel material DiS-AC promises to be an ideal candidate for filters treating stormwater runoff.
A catalytic role of surface silanol groups in CO2 capture on the amine-anchored silica support
A new mechanism of CO2 capture on the amine-functionalized silica support is demonstrated using density functional theory calculations, in which the silica surface not only acts as a support to anchor amines, but also can actively participate in the CO2 capture process through a facile proton transfer reaction with the amine groups. The surface-mediated proton transfer mechanism in forming a carbamate–ammonium product has lower kinetic barrier (8.1 kcal mol−1) than the generally accepted intermolecular mechanism (12.7 kcal mol−1) under dry conditions, and comparable to that of the water-assisted intermolecular mechanism (6.0 kcal mol−1) under humid conditions. These findings suggest that the CO2 adsorption on the amine-anchored silica surface would mostly occur via the rate-determining proton transfer step that is catalyzed by the surface silanol groups.
Molecular insights into benzimidazole-linked polymer interactions with carbon dioxide and nitrogen
Investigation of the binding affinity gases on porous adsorbents are important for establishing understanding of effective carbon dioxide adsorption and design target specific sorbents for capturing hazardous gases for environmental protection and fuel upgrading. A density functional theory (DFT) study that highlights the impact of benzimidazole-linked polymer structure design has been conducted to explain the molecular and electronic structure, investigate the interaction sites and elucidate the experimental results on carbon dioxide and nitrogen sorption on these porous structures. DFT calculations were used to infer the strength of the polymer – gas interaction modes as well as to quantify short-range interactions between the polymer – gas via topological characteristic
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