Linker functionalised phosphinate metal-organic frameworks: Adsorbents for the removal of emerging pollutants

Metal-organic frameworks (MOFs) are attracting increasing attention as adsorbents of contaminants of emerging concern which are difficult to remove by conventional processes. However, common carboxylate-based MOFs suffer from low stability in water environment, which limits their environmental applications. In this study, we use phosphinate-based MOFs with higher hydrolytic stability and we focus on the influence of functional groups covering the pore walls on the adsorption of pharmaceutical pollutants present in water – diclofenac, cephalexin and sulfamethoxazole. We present a synthesis of new structures isoreticular to the phosphinate MOF ICR-7. The presented MOFs contain phenyl rings facing the pore walls modified with dimethylamino groups (ICR-8) and ethyl carboxylate groups (ICR-14). These functionalized MOFs were obtained from two newly synthetized phospinate linkers containing the respective functional groups. Generally, the presence of additional functional groups resulted in higher affinity to the tested pollutants in comparison with ICR-7 or activated carbon, however, it also decreased the sorption capacity.