Core/Shell PDA@UiO-66 Metal-Organic Framework Nanoparticles for Efficient Visible-Light Photodegradation of Organic Dyes

In this study, bio-inspired polydopamine nanoparticles (PDA NPs) were utilized as a starting template to fabricate a well-defined zirconium-based MOF (UiO-66, PDA@MOF) core/shell heteronanostructures for visible light-emitting diode (LED) light-assisted photocatalytic applications. The selected PDA substrate provided a multifunctional starting platform for one-pot nucleation growth of metal-organic frameworks (MOF) shell layer with regular spherical morphologies (similar to 350 nm in size), as well as monodisperse size distribution. The obtained band properties of PDA@MOF (E-CB = -1.10 eV and E-VB = 1.85 eV vs normal hydrogen electrode (NHE)) revealed that the synthesized nanostructures could promote the reduction of oxygen to superoxide anions (O-2(center dot-)) and the formation of HO center dot for effective visible LED-light-irradiated photocatalytic degradation of MB. To accelerate the photocatalytic decolorization of MB, an electron acceptor (i.e., H2O2) was utilized, which effectively surpassed the electron-hole recombination by trapping electron and producing more hydroxyl radicals. Therefore, a remarkable photocatalytic performance was recorded using PDA@MOF, in which similar to 99% of MB was decolorized within 80 min under visible LED light illumination thanks to the well-defined core/shell structure, high surface area, convenient band gap, effective molecular sieving due to the regular/identifiable morphology, as well as good dispersity in reaction medium. Owing to the advantages of PDA@MOF nanoparticles, the photoelectrochemical (PEC) water splitting performance with highest photocurrent density was obtained as 1.53 mA/cm(2) at low potential 0.28 V vs RHE under visible LED illumination, which is similar to 20-fold higher than dark conditions (0.07 mA/cm(2)). This study mainly highlighted the great potential of MOF-based core/shell nanostructures with uniform/regular morphologies as a next generation of visible-light-responsive catalysts for various environmental applications.