(521c) Designing Supported Metal Nanoparticle Catalysts Leveraging Hydrogen Bonding Interactions and a New Class of Supramolecular Supports

Supported metal nanoparticles (NPs) constitute an important class of catalytic materials with wide-ranging applications in C-C coupling, hydrogenation, and redox routes. Several techniques have been developed to achieve highly dispersed, size-controlled metal NPs on diverse supports, including ligand-based approaches (e.g., colloidal methods, sol-immobilization) as well as support surface functionalization (e.g., graphene oxidation to graphene oxide). While effective, these approaches often forego the electronic structure of the pristine NP surface due to the presence of surface-bound ligands and/or strong metal-support interactions (SMSIs), which can obfuscate crucial structure-function insights that guide rational catalyst design. Furthermore, they can be process intensive and involve harsh reagents, toxic solvents, etc.

To sidestep these challenges, in this talk, we will present a new synthetic protocol to functionalize a supramolecular support, melamine cyanurate (MCA), with metal NPs leveraging hydrogen bonding interactions at mild conditions (aqueous solvent, 80 °C). We show that by using a functionalized N-heterocycle ligand, MTT (Figure 1a), we can anchor and disperse metal precursors onto the MCA support at the thiol functionality, and obtain small, uniform, and highly dispersed ~3 nm NPs upon thermal treatment in H₂ (Figure 1b). We will show that MCA-supported Au NPs prepared in this way outperform conventional synthesis methods in the aerobic oxidation of piperidone as a model test reaction (Figure 1c). High-resolution XPS analysis reveals that while the Au NPs and MCA lack SMSIs, the Au-MCA interface redistributes charge in the N and O atoms in MCA that may contribute to impressive NP stability, even in the absence of SMSIs and/or ligands. Finally, we will demonstrate how this approach generalizes to creating NPs of different size and with different compositions. More broadly, we expect this to outline a versatile strategy to preparing supported NP catalysts with highly tailored properties, leveraging hydrogen bonding interactions as a design lever.