Ligand stabilized Au9 nanocluster Integrated with HKUST-1: In-Depth Structural analysis and Interfacial Electronic Coupling Kinetics

Abstract

Metal nanoclusters hold immense potential for catalysis, energy storage, and optoelectronics due to their quantum confined properties, yet achieving precise atomic level structural control remains a key challenge. This study investigates the ligand directed assembly of rac-BINAP stabilized Au9 NC using single crystal X-ray diffraction, revealing a distorted crown like Au9 core (P-1 space group) with C2 symmetry. The structure of metallic core is decided by two key ligand interactions: (1) C–H···π forces of interactions between BINAP phenyl rings that cause elongation of corresponding Au–Au bonds length, and (2) asymmetric Au–P interactions controlled by protecting ligands. These interactions control the ultimate assembly of Au9 NC, with a central Au atom and peripheral Au sites. Furthermore, by integrating Au9 NC into HKUST-1 via in-situ synthetic method, we developed electrode for supercapacitor application with a specific capacitance of 331 Fg-1 which is 2.6 times higher than pristine HKUST-1, attributed to homogeneous dispersion and consequent enhanced charge transfer kinetics in in-situ integrated Au9 NC/HKUST-1 composite. Current findings were further corroborated by theoretical calculation, indicating directional transfer of electronic density from Au9 NC to HKUST-1. This work establishes a framework for designing NC through precise ligand engineering, advancing the development of high-performance nanomaterials for energy storage and beyond.