The photocatalytic
efficiency of ecofriendly Keplerate {Mo72Fe30} nanoclusters in degradation of hazardous
organic dyes such as rhodamine B (RhB) under visible/solar light is
exploited. A higher photoremoval activity was observed for amorphous
{Mo72Fe30} than its crystalline counterparts
and other Keplerates. The greater specific surface area (SBET) and,
particularly, pore volume (V
BJH) of the
amorphous {Mo72Fe30} cluster than those of its rhombohedral crystal (3-
and 28-fold for SBET and V
BJH, respectively)
as well as negative charges on its surface (ζ = −16.2
mv) are important factors for such a superiority. The negative effect
of increasing the pH of the solution on the removal rate along with
scavenging experiments and photoluminescence (PL) study excluded the
involvement of OH• in photodegradation process.
Instead, an electron transfer from the excited dye (RhB*) to the POM
producing RhB
+·
, and reduced POM (POM–) is postulated as a possible mechanism for photoassisted
degradation of dye under visible light. The nanocluster proved to
be a recyclable photocatalyst with high durability as evidenced by
FT-IR, Raman, XRD, EDX, and XPS spectral data.