Controlled-release fertilizers (CRFs) are sustainable
alternatives
as they can increase crop yield and minimize environmental contamination
associated with conventional fertilizers. However, there remains a
demand for the development of CRFs with high biocompatibility, and
tunable morphologies and mechanical properties. Herein, a solvent-free
mechanochemical method is developed for synthesizing urea-encapsulated
metal–phenolic networks (urea–MPN matrices) as CRFs.
The matrices exhibit tunable mechanical resistance, crystallinity,
stiffness, and wettability properties via rearranging the internal
structure of the MPNs and their subsequent interaction with the encapsulated
urea crystals. Sample aging (7 days) leads to a higher degree of complexation
of the MPNs, resulting in a material with increased elasticity and
melting point relative to the as-synthesized sample. Thermal treatment
(60 °C for 6 h) instigates structural reorganization of the urea
crystals within the matrix, generating a more robust material with
a 51-fold increase in Young’s modulus. As CRFs, the urea–MPN
matrices can be tuned to prolong the release of urea for up to 9 days
depending on the treatment applied. As the mechanochemical synthesis
of MPNs facilitates the tuning of physiochemical properties and has
greater practicability for inclusion within large-scale processing,
it has potential implementation within a broad range of industries.