Functionalized metal–organic framework as a new platform for efficient and selective removal of cadmium(ii) from aqueous solution

In this work, we illustrate how to anchor –SO3H functional groups onto the pore surface of MOF for cadmium removal from aqueous solution via the approach of sequential post-synthetic modification and oxidation as exemplified in the context of functionalizing the MOF, Cu3(BTC)2 with sulfonic acid. The resultant sulfonic acid functionalized MOF, Cu3(BTC)2–SO3H demonstrates a high cadmium uptake capacity of 88.7 mg g−1, surpassing that of the benchmark adsorbents. In addition, it exhibits a fast kinetics with the kinetic rate constant k2 of 0.6818 g mg−1 min, which is 1–3 orders of magnitude higher than existing adsorbent materials for adsorbing cadmium ions from aqueous solution. Moreover, it demonstrates high selectivity of cadmium ions in the presents of other background metal ions, and can be readily regenerated and recycled without significant loss of cadmium uptake capacity. Our work thus paves a way for developing functionalized MOFs as a new type of platform for removing cadmium from wastewater.