Controlled Magnesium Release and Nutritional Effect of a Novel Metal-Organic Framework on Plants

Fertilizer application is a necessary action in modern agriculture to meet the global food demand. Modern agriculture must enhance crop production while minimizing the amounts of used fertilizers to ensure environmental safety without compromising their effectiveness. One promising approach to achieve this ambitious goal is using controlled-release fertilizers, which provide an effective amount of active ingredients prolonged over time while reducing the losses caused by leaching into the soil. In this work, a novel metal-organic framework (MOF) [Mg₂(C₃H₇O₅P)₂(H₂O)₄]·H₂O, named GR-MOF-27, based on the antibacterial agent fosfomycin (FMC) and magnesium is reported. First, its crystal structure was determined by single-crystal X-ray diffraction, and then its stability in aqueous media was studied. The results showed a prolonged two-step release of Mg²⁺ ions (release rates of 26% in 4 h and 63% in 7 d), which fits to pseudo-first-order kinetic (first 4 h) and pseudo-second-order (from 4 h to 7 d) release models. Since the metal precursor (magnesium sulfate) is normally used as a fertilizer, the nutritional effects of GR-MOF-27 and MgSO₄ were evaluated and compared, obtaining the result that GR-MOF-27 improves plant growth by increasing shoot, root, and dried weight by 10.5, 11.0, and 13.1%, respectively. Additionally, plants treated with GR-MOF-27 showed an increase in the uptake of important macronutrients, such as 64.9% of Mg and 57.4% of P, demonstrating the benefits of using MOFs as slow-release fertilizers.