A study on a novel MIL-100(Fe)@UREA Nano-Fertilizer with high loading capacity and superior sustained-release performance

To overcome the low nitrogen use efficiency (<40%) of conventional urea, this study utilizes the metal–organic framework MIL-100(Fe)—characterized by ultrahigh surface area and tunable mesoporosity—as a promising carrier for nano slow-release fertilizers with enhanced nutrient stability. Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller measurements confirmed that urea was uniformly accommodated within the MOF channels in an amorphous, physically adsorbed state without chemical bonding. High-performance liquid chromatography revealed that loading capacity was primarily determined by the urea-to-MOF mass ratio, whereas loading temperature and duration had negligible effects, enabling precise synthesis control. Orthogonal optimization identified the optimal parameters (mass ratio 1:1, 110°C, 7 h), yielding a urea loading of 59.2% and encapsulation efficiency of 51.8%. Release experiments demonstrated a 22.5-fold extension in release duration compared to pure urea, with 87.6% cumulative release over 180 h governed by Fickian diffusion. Furthermore, physical characterization and bench-scale metering tests verified the granules' mechanical adaptability, achieving stable, continuous discharge comparable to urea. This work validates MIL-100(Fe)@UREA as a high-capacity, mechanically viable platform for sustainable and precision nutrient delivery. These results not only highlight the potential of MIL-100(Fe) in advanced slow-release fertilizer systems but also provide valuable insights for designing efficient and environmentally sustainable nutrient delivery platforms.