Alkaline treatment in 0.2 and 0.4 M NaOH solutions successfully generated controlled
mesoporosity into ZSM-5 (Zeolite Socony Mobil-5) zeolite, resulting in average mesopore
diameters of approximately 15 and 25 nm, respectively, while preserving the crystalline
structure of the zeolite framework. Parent ZSM-5 and its mesoporous derivatives obtained
by desilication were used to prepare (Fe species)@(zeolite matrix) composites. The synthesis
was carried out by co-precipitating Fe2+/Fe3+ ions onto both parent and desilicated ZSM-5
matrices under oxygen-free conditions. Comprehensive characterization by X-ray diffraction,
scanning electron microscopy, N2 adsorption, vibrating-sample magnetometry, 57Fe
Mössbauer spectroscopy, and diffuse reflectance UV–Vis spectroscopy revealed that the
degree of introduced mesoporosity dramatically influences the size, dispersion, phase composition,
and oxidation state of the iron-containing nanospecies. On purely microporous
ZSM-5, relatively large (~15 nm) partially oxidized magnetite nanoparticles are formed predominantly
on the external surface, exhibiting superparamagnetism at room temperature
(Ms = 11 emu/g) and a band gap of 2.12 eV. Increasing mesoporosity leads to progressively
smaller and more highly dispersed iron(III) oxo/hydroxo clusters with significantly
lower blocking temperatures and reduced magnetization (down to 0.7 emu/g for Fe@ZSM-
5_0.4). All composites display strong visible-light absorption confirming their potential as
magnetically separable visible-light-driven photocatalysts for environmental remediation.