Biomimetic 1‑Aminocyclopropane-1-Carboxylic Acid Oxidase Ethylene Production by MIL-100(Fe)-Based Materials

A novel
core@shell hybrid material based on biocompatible hydroxyapatite
nanoparticles (HA) and the well-known MIL-100­(Fe) (Fe3O­(H2O)2F­(BTC)2·nH2O, BTC: 1,3,5-benzenetricarboxylate) has been prepared following
a layer-by-layer strategy. The core@shell nature of the studied system
has been confirmed by infrared, X-ray powder diffraction, N2 adsorption, transmission electron microscopy imaging, and EDS analyses
revealing the homogeneous deposition of MIL-100­(Fe) on HA, leading
to HA@MIL-100­(Fe) rod-shaped nanoparticles with a 7 nm shell thickness.
Moreover, both MIL-100­(Fe) and HA@MIL-100­(Fe) have demonstrated to
act as efficient heterogeneous catalysts toward the biomimetic oxidation
of 1-aminocyclopropane-1-carboxylic acid into ethylene gas, a stimulator
that regulates fruit ripening. Indeed, the hybrid material maintains
the catalytic properties of pristine MIL-100­(Fe) reaching 40% of conversion
after only 20 min. Finally, the chemical stability of the catalyst
in water has also been monitored for 21 days by inductively coupled
plasma-mass spectrometry confirming that only ca. 3% of Ca is leached.