bcmubx2102 – Amino acid encoded Metal-Organic Framework adsorbents for heavy metals

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• June 21, 2021
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Poster-Ainara-Valverde2

Abstract

Metal-Organic Frameworks (MOFs) have emerged as highly promising porous and crystalline materials to address heavy metal pollution, overcoming the adsorbing capacities and kinetics of classic adsorbents [1]. MOFs are formed by easily tunable inorganic and organic building blocks arranged in a porous and ordered fashion, creating a crystalline structure with large surface areas. Among all the broad variety of MOFs, Zr (IV) based ones, like MOF-808, have attracted the attention of the scientific community because of their great water stability, even in acidic conditions. However, the majority of Zr-MOFs show little selectivity towards heavy metal ion capture [2], which can be overcome encoding –SH, –NH₂ or –COOH functionalities into their structures. In these work, cysteine, histidine and citric acid have been post-synthetically anchored to the uncoordinated positions of Zr hexanuclear clusters of MOF-808, in order to increase its adsorption affinity over metal cations with different acidities. In fact, MOF-808 has six uncoordinated positions per cluster where formate molecules are found. Amino acids and natural acids can easily replace formate anions mimicking their binding mechanism to the cluster through the carboxyl groups [3]. Final encoding provides the pores of MOF-808 with amino acid residual groups able to act as metal-adsorption sites (Fig. 1) similar to the ones found in many metalloproteins active cores.

Figure 1. Post-synthetic functionalization of MOF-808 with cysteine and possible metal adsorbing sites.

Acknowledgement: The authors thank Spanish Ministry of Economy and Competitiveness (MINECO) for financial support through projects MAT2016-76739-R (AEI/FEDER, UE). To the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK AND PIBA (PIBA-2018-06) programs H2020-MSCA-RISE-2017 (Ref: 778412)  INDESMOF project. Ainara Valverde acknowledges the Basque Government (Education Department) for her PhD grant (PREB_2018_1_004) that made this work possible.

Keywords: Metal-Organic Framework, Heavy Metal, Adsorption, Post-synthetic functionalization

References: [1] P. Kumar, A. Pournar, K. Kim,  Progress in Materials Science 2017, 86, 25–74. [2] Y. Peng, H. Huang, Y. Zhang,  Nature Communications,  2018, 9, 1–9. [3] S. S. Dhankhar, C. M. Nagaraja,  New J. Chem,  2019, 43, 2163–2170.