Metal Organic Framework advanced adsorbents for metal ions recovery from polluted water sources

Mining and industrial activities, as well as in some cases natural geological environments, are continuous heavy metal pollution sources of water basins [1]. Among the currently applied technologies to remove heavy metals, adsorption is one of the most interesting ones due to its low energy consumption, easy applicability and reusability. In that respect, Metal Organic Frameworks (MOFs) have emerged as highly promising porous materials to address heavy metal pollution, overcoming the adsorbing capacities and kinetics of heavy metals reported for classic adsorbents [2]. Concretely, Zr (IV) based MOFs like MOF-808 have attracted lots of attention because of their great water-stability even in acidic conditions. However, they show little selectivity towards heavy metal ion capture [3]. MOF-808 is constructed from Zr-hexanuclear clusters (Zr6) that contain twelve possible positions where the carboxylate linkers can be anchored (Fig. 1(a)). Depending on the organic linker and synthesis conditions, six to twelve positions can be occupied by the carboxylate groups of the organic ligands (trimesic acid), being the positions not capped by the organic connectors the preferential functionalization positions for being functionalized, as they are occupied with formates that are easy to replace (Fig. 1 (b)) [4].