Adsorption of Nitrogen-Containing Compounds from Model Fuel over

Dec 15, 2015 - Interestingly, the adsorbed amount of QUI decreased with increasing content of —SO3H in UiO-66 when the QUI concentration was high (i...
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Adsorption of Nitrogen-Containing Compounds from Model Fuel over Sulfonated Metal-Organic Framework: Contribution of Hydrogen-Bonding and Acid-Base Interactions in Adsorption Imteaz Ahmed, Minman Tong, Jong Won Jun, Chongli Zhong, and Sung Hwa Jhung J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b10578 • Publication Date (Web): 15 Dec 2015 Downloaded from http://pubs.acs.org on December 22, 2015

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The Journal of Physical Chemistry

Adsorption of Nitrogen-Containing Compounds from Model Fuel over Sulfonated Metal-Organic Framework: Contribution of Hydrogen-Bonding and Acid-Base Interactions in Adsorption Imteaz Ahmed,a, ‡ Minman Tong,b, ‡ Jong Won Jun,a Chongli Zhong,*b Sung Hwa Jhung*a a

Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National

University, Daegu 702-701, Republic of Korea. b

State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical

Technology, Beijing 100029, China.

Abstract Adsorptive denitrogenation (ADN) was carried out by adsorption of indole (IND) and quinoline (QUI) over metal-organic frameworks (MOFs) including acidic UiO-66-SO3H for the first time. The adsorbed amount of IND increased with increasing content of –SO3H in UiO-66. The favorable effect of the –SO3H group on the adsorptive removal of IND could be explained by hydrogen bonding between the O of –SO3H and the H of IND, which was firmly supported by

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the adsorption of pyrrole and methylpyrrole and by theoretical calculations. The application of a –SO3H group in the adsorptive removal of neutral IND is meaningful since neutral nitrogencontaining compounds are not easy to remove and since UiO-66-SO3H is reusable after simple washing with ethanol. The expected increase in QUI adsorption (due to acid-base interaction) with acidic –SO3H was observed when QUI was present at low concentrations ( 3 Å) was found between one H atom (on C of QUI) and the O atom (of –S=O) (Figure S3(b)). Curiously, the

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calculated adsorption energies are similar each other (-212.5 and -228.5 kJ/mol for the first and second QUI, respectively), suggesting that the second QUI molecule might be adsorbed favorably if other conditions such as steric hindrance are not strict. Since the calculation results suggested that the concentration of QUI might have an influence on its adsorption behavior, we decided to carry out the adsorption of QUI at different concentrations and found an interesting result that might agree with the calculation results. Figure 6 shows the adsorption results of QUI over UiO-66 and UiO-66-SO3H(18) for different initial QUI concentrations for three adsorption times. Irrespective of adsorption time, UiO-66SO3H(18) showed higher adsorption performance for QUI than pristine UiO-66 at low initial QUI concentrations (