Silver nanoparticles-based thioureidophosphonate composites: Synthesis approach and their exploitation in 4-nitrophenol reduction

Two novel mono- and bis-thioureidophosphonate cores (referred by MTP & BTP, respectively) were facilely synthesized in ionic liquid conditions and incorporated with silver nanoparticles (Ag NPs) via in-situ reduction method giving two heterogeneous nanocatalysts, denoted as Ag NP/MTP and Ag NP/BTP, respectively. X-ray diffraction (XRD), ultraviolet-visible (UV–Vis), and high-resolution transmission electron microscopy (HR-TEM) tools were conducted for the as-fabricated Ag NP/TP nanocomposites revealing the good dispersion of Ag NPs in spherical black dots with average size ranges of (∼9.5–12.7 nm) and (∼17.0–22.5 nm) for Ag NP/MTP and Ag NP/BTP, respectively. The Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques clarified that, MTP possessing (POPh, PO, C=S, HCO, and >NH) functionalities were participated in the reduction of Ag+ ions to Ag0 NPs. The catalytic properties of both Ag NP/TP nanocomposites were verified through the chemical conversion of 4-nitrophenol (4-NP) to less hazardous 4-aminophenol (4-AP) comparable to the slight catalytic reduction of Ag NPs-free TP derivatives. To assess the catalytic performance, some kinetic parameters such as rate constant (Kapp), normalized rate constant (Knor), and turnover frequency (TOF) were estimated at the highest concentration of 4-NP. Accordingly, Ag NP/MTP exhibited more remarkable catalytic activity and durability toward 4-NP reduction than that of Ag NP/BTP. The simple stereochemistry and accessibility of active sites for MTP tuned the surface function with Ag+ ions, affording more stable and regular Ag NPs over the same nanoparticle with BTP. Regarding Ag NP/MTP, catalytic improvement rates to 69%, 64%, and 69% were respectively recorded for Kapp, Knor, and TOF over Ag NP/BTP. Moreover, both nanocatalysts demonstrated good surficial stability through 10 consecutive cycles. Herein, this study has provided a new sustainable route for developing new TP-wrapped metal nanocomposites as robust and selective platforms in catalytic and environmental applications. [Display omitted]