New crosslinked cyclodextrin-based MOFs for the removal of Emerging Contaminants

Emerging Contaminants (ECs) are becoming a major concern of our time, as they pose a serious threat to human health and
ecosystems. ECs are synthetic or natural occurring compounds, released to the environment by human activities, that are not
currently regulated by environmental laws. Specifically, they derive from pharmaceuticals, pesticides, cosmetics and industrial
chemicals. Traces of ECs have been detected even in drinking water and food sources. As the effects of long-term exposure to ECs
are still unknown, finding new methods to efficiently sequester and remove ECs from the environment is of primary importance.
In this project, we propose to develop and study a new typology of highly porous crystalline nanosponges for the adsorption and
removal of ECs from contaminated water. These NSs are derived from safe, cost-effective and sustainable metal organic frameworks
(MOFs) prepared by simply mixing cyclodextrins (CDs) with metal ions (e.g., K, Na, etc.). CD-MOFs exhibit high surface area (i.e.,
hundreds m2/g) and remarkable gas adsorption capacity. However, the use of CD-MOFs in aqueous media is not convenient due to
their solubility. To overcome such limitation, crosslinking reactions of pre-formed CD-MOFs can be carried out to stabilize their
crystalline structure, making it insoluble in all solvents. These crystalline CD nanosponges (CD-MOF-NSs) exhibit higher surface area
than the analogous amorphous CD-NSs described in the literature. The reason lies in their ordered structure and accessible bulk
microporosity. As the amorphous CD-NSs have been widely studied for water decontamination, showing a sequestering capacity
comparable or, in some specific cases, even higher than commercial adsorbents, CD-MOF-NSs would be a further evolution of this
technology.
Unlike the majority of adsorbents, CD-MOF-NSs offer the advantage of having two kinds of pores: the internal cavity of the CD
molecule, which is lipophilic and can host organic non-polar pollutants and the interstitial voids between CD molecules, which are
hydrophilic and able to segregate polar pollutants. Metal ions could be captured as well, if a crosslinker bearing acid groups is
selected. All these features make CD-MOF-NSs a remarkably versatile tool whose sequestering capacity remains almost entirely
unexplored.
In this project, a team of three units having great experience in the field and complementary knowledge will prepare, characterize and test different formulations of CD-MOF-NSs. The syntheses will be performed tuning a number of experimental parameters and
then optimized in accordance with the principles of Green Chemistry. All the samples will be thoroughly studied to determine their
chemical composition and crystalline structure. Afterwards, the prepared crystalline NSs will be used for removing ECs from
contaminated water through in-batch and in-flux modes. Finally, the possibility to recycle or regenerate the MOF-NSs will be
investigated as well.