Optimization of metal–organic (citric acid) frameworks for controlled release of nutrients

Although polymer-coated controlled-release fertilizers have been under development for decades, their high costs, complex production processes, and potential environmental hazards have limited their application. Therefore, it is necessary to design and develop new materials for controlled nutrient release. In this study, two novel MOFs, compounds I and II, were successfully fabricated and optimized using ferric chloride, phosphoric acid, citric acid, and urea under hydrothermal conditions. The N, P, and Fe contents in compound I were 9.05%, 14.92%, and 14.55%, respectively, while the corresponding values in compound II were 10.78%, 14.10%, and 16.68%. The soil incubation results revealed that both compounds showed good slow-release longevity (more than 100 days). This study provides a new strategy for the fabrication of novel controlled-release fertilizers.