Synergistic Electronic Effects in AuCo Nanoparticles Stabilized in a Triazine-Based Covalent Organic Framework: A Catalyst for Methyl Orange and Methylene Blue Reduction

Abstract

Developing stable active catalysts for reducing water-soluble pollutants is a desirable target. In this pursuit, we have functionalized covalent organic frameworks (COFs) with gold (Au) and cobalt (Co) nanoparticles via a one-step aqueous synthesis process, and their catalytic activity in reducing methyl orange and methylene blue is examined. Operando absorbance measurements of methyl orange (anionic dye) reduction revealed AuCoCOF (1.3 Au/1.0 Co) to have superior kinetics over many other catalysts, which typically require additional external stimuli (e.g., photons) and higher catalyst loadings. After confirming the homogeneous dispersion of the nanoparticles on the COF support using three-dimensional (3D) tomography and material stability through powder X-ray diffraction (PXRD), infrared (IR), and thermal studies, we investigated their redox activity. Cyclic voltammetry (CV) confirmed the involvement of both metals in the redox process, while spectroelectrochemical measurements show that their activity and kinetics remain unaltered by an applied potential. Solid-state UV measurements reveal that the neat COF is a semiconductor with a large band gap (2.8 eV), which is substantially lowered when loaded with cobalt nanoparticles (2.2 eV for CoCOF). The electronic synergy between Au and Co nanoparticles further reduces the band gap of AuCoCOF (1.9 eV). Thus, there is a definite advantage in doping non-noble metal nanoparticles into a noble metal lattice and nanoconfining them into a porous COF support. Our study highlights the significance of bimetallic COF-supported nanocatalysts, wherein one can engage each component toward targeted applications that demand redox activity with favorable kinetics.

Tailoring COFs: Transforming Nonconducting 2D Layered COF into a Conducting Quasi-3D Architecture via Interlayer Knitting with Polypyrrole

“…To demonstrate the feasibility of the proposed protocol shown in Scheme , we first synthesized a (3 + 2) nitro-functionalized framework as COF20-NO 2 through a Schiff base condensation reaction of 2,4,6-triformyl resorcinol and 2-nitro-1,4-phenelynediamine under solvothermal conditions. − Starting from this nitro-functionalized COF, via postsynthetic modification, which includes a reduction to amine, , followed by Clauson–Kaas pyrrole modification − employing dimethoxy-THF and then an oxidative polymerization with iodine as a catalyst, we prepare the COF20-Ppy. The COFs were isolated in every step and characterized thoroughly.…”

Doped metal clusters as bimetallic AuCo nanocatalysts: insights into structural dynamics and correlation with catalytic activity byin situspectroscopy

“…As these nanoalloys are formed by rearrangement of metal atoms during pretreatment and reaction, and due to the defined structure of the clusters, it is possible to understand their evolution using spectroscopic techniques. 9 Another interesting bimetallic system is Co-Au, since the physicochemical properties of both metals complement each other and enhance, among others, the magnetic 15,16 , catalytic 17,18 or electrocatalytic 19,20 properties. Moreover, the synergy of the biocompatibility of Au and the magnetic properties of Co expands its applicability to biomedicine and biodiagnostics.…”

“…Another interesting bimetallic system is Co–Au, since the physicochemical properties of both metals complement each other and enhance, among others, the magnetic, 15,16 catalytic 17,18 or electrocatalytic 19,20 properties. Moreover, the synergy of the biocompatibility of Au and the magnetic properties of Co expands its applicability to biomedicine and biodiagnostics.…”

COF-supported zirconium oxyhydroxide as a versatile heterogeneous catalyst for Knoevenagel condensation and nerve agent hydrolysis

“… 1 , 2 , 3 In addition to covalent bonding, ubiquitous hydrogen bonding and π-stacking interactions in COFs result in robust 2D/3D structures and protect them from hydrolysis and solvation. 4 , 5 Due to a diversity in the composition, structure, and properties, COFs are employed in a myriad of applications such as electrocatalysis, 6 charge storage, 7 dye degradation, 8 water remediation, 9 , 10 , 11 gas sorption, 12 storage and separation, 13 deposition/stabilization of metal nanoparticles (NPs), 8 and heterogeneous catalysis. 1 , 8 , 14 …”