Fe-carbon nanofiber-modified Mo-MOF for the controlled release and translocation of micronutrients in plants

Transition metals such as iron (Fe), molybdenum (Mo), copper (Cu), and zinc (Zn) at low concentrations are essential for plant growth and development. However, they may turn toxic beyond a threshold level. Therefore, a regulated supplement of these elemental micronutrients is important for achieving optimal effects on plant growth and nutritional quality. In the present study, we have developed a Fe-carbon nanofibers (CNF)-modified Mo-metal organic framework (MOF) that can release Fe-CNF and Mo upon microbial degradation in soil. CNF facilitates the translocation of Fe and Mo in plants. The synthesized Fe-CNF/Mo-MOF was characterized for physicochemical properties by applying a range of analytical techniques e.g., SEM-EDX, TEM, DLS, AAS, XRD, FTIR, and XPS. A gradual degradation of the Mo-MOF was observed in soil for 30 days, using scanning and transmission electron microscopy and Raman spectroscopy. Plant growth studies were performed using Cicer arietinum as a model plant. Our results showed that supplementing a low dose (0.22 g kg-1 soil) of Fe-CNF/Mo-MOF to soil was sufficient for the metals to reach plants, which subsequently improved plant growth (indicated by increased fresh biomass and root-shoot lengths) and nutritional quality (indicated by an increase in nitrogen, protein and chlorophyll contents). Although the present study is focused on the delivery of Fe and Mo, we believe that the developed material has a potentially broad applicability for supplementing the other mineral nutrients, including biomolecules. Fe-CNF/Mo-MOF releases Mo and Fe in soil upon degradation by resident rhizobacteria and translocates the micronutrients to plant roots, shoots, and leaves.