**5.4 Metal: organic frameworks**

There is an emerging class of F adsorbents in fabricated metal–organic frameworks. This are basically multivalent metal ions intercalated in large organic molecules to enhance the synergic F uptake by the metal ions and the organic substrates. Jeyaseelan et al. [106] investigated defluoridation capacities of three MOF's including fumaric acid–based metal–organic frameworks (MOFs) using Zr4+, La3+, and Fe3+ metal ions and found that they had comparable defluoridation capacities of 4.920, 4.925, and 4.845 mg/g, respectively.

### **5.5 Carbonaceous adsorbents**

Carbonaceous F adsorbents include activated carbons from plants and animal biomasses, carbonaceous mineral adsorbents, and graphene.
