Mithun Sarker

Carboxylic-acid-functionalized UiO-66-NH2: A promising adsorbent for both aqueous- and non-aqueous-phase adsorptions

Mithun Sarker, Ji Yoon Song and Sung Hwa Jhung
Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 41566, Republic of Korea.
Abstract
UiO-66 functionalized with -NH- and -COOH groups was obtained by postsynthetic modification of aminated UiO-66. In order to introduce uncoordinated carboxyl groups into metal-organic frameworks (MOFs), UiO-66-NH2 was treated with oxalyl chloride to form UiO-66 functionalized with -NH- and -COOH groups (UiO-66-NH-CO-COOH). The successful functionalization of the MOF with uncoordinated carboxyl group was confirmed using some characterization techniques. The obtained MOFs were applied in liquid-phase adsorptions for both water and a model fuel. The UiO-66-NH-CO-COOH, consisting of dual functional groups (-NH- and -COOH), showed better performance than pristineUiO-66,UiO-66-NH2,and commercial activated carbon (AC)in the removal of several organics, e.g. triclosan (TCS) from water, and indole (IND) and quinoline (QUI) from model fuel. The UiO-66-NH-CO-COOH adsorbed ~2.4 and 5.5 times more TCS and IND, respectively, than AC and its adsorption performances were comparable with other reported adsorbents. The remarkable adsorption efficiency of the MOF for both aqueous and non-aqueous phases was explained in terms of H-bonding: UiO-66-NH-CO-COOH and adsorbates act as H-bond acceptor and H-bond donor, respectively. Moreover, UiO-66-NH-CO-COOH can be regenerated by simple solvent washing and can be reused several times for the removal of the studied adsorbates. Therefore, UiO-66-NH-CO-COOH having both -NH- and -COOH groups is recommended as a versatile adsorbent for both aqueous- and non-aqueous-phase adsorptions.
Keywords: adsorption; H-bonding; metal-organic frameworks; UiO-66; zwitterions


Reference:

M. Sarker, J.Y. Song, S.H. Jhung, Carboxylic-acid-functionalized UiO-66-NH2: A promising adsorbent for both aqueous- and non-aqueous-phase adsorptions, Chem. Eng. J. 331 (2018) 124-131.
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