Pd-Embedded Ti Metal–Organic Framework Nanostructures for Photocatalytic Reductive N-Formylation of Nitroarenes in Water

Abstract

The photocatalytic reductive N-formylation of nitroarenes is carried out over a Pd nanoparticle (Pd NP)-embedded nanostructured Ti-metal–organic framework (MOF) using sunlight or a household white light-emitting diode (LED). Herein, the Ti-MOF is used as a visible-light-absorbing material, and the Pd NPs boost the photogenerated charge-carrier separation and transfer to the active sites for catalyzing the photocatalytic N-formylation of nitroarenes. The surface characteristics, oxidation states, and elemental compositions of the nanostructured materials were characterized by several physicochemical characterization techniques. Optical property and photoelectrochemical measurements were conducted to determine the bandgap, electron–hole recombination rate, band edge potentials, photocurrent density, charge-carrier separation, and so on. N-formylation of nitroarenes was achieved using HCOOH as a sustainable hydrogen and formylating source with simple household white LED bulbs. The yield of N-formylated arene was excellent in an aqueous medium. The structure–activity relationship was revealed using photocatalytic activity data, physicochemical and optoelectronic characteristics, control experiments, and scavenging studies. The high photocatalytic performance of the Pd/Ti-MOF can be ascribed to the direct contact between the Pd NPs and MOF, the generation of abundant catalytically active sites, and the superior electrical conductivity that leads to rapid electron transfer processes. The Pd/Ti-MOF exhibited excellent photostability and recyclability. The efficient catalyst design, an economical and sustainable light source for the direct formylation of nitroarenes, would attract researchers to develop similar catalytic protocols to other industrially important chemicals.