Molecular-scale insight into the heteroepitaxial growth of oriented Cu-paddlewheel-based metal–organic frameworks on Cu(OH)2 mediated by pre-organized linker domains

Fabricating three-dimensionally (3D) oriented metal–organic framework (MOF) thin films is essential for exploiting their anisotropic functionalities in advanced device applications. Although heteroepitaxial growth of Cu-paddlewheel MOFs on sacrificial Cu(OH) 2 nanobelts has emerged as a powerful method, the molecular-scale processes governing nucleation and orientation at the organic-inorganic interface remain elusive. In this study, we provide a comprehensive investigation into the early-stage growth mechanism of [Cu 2 (1,4-benzenedicarboxylate) 2 (1,4-diazabicyclo[2.2.2]octane)] on Cu(OH) 2 by leveraging the synergistic capabilities of atomic force microscopy (AFM) and polarization-dependent infrared spectroscopy in attenuated total reflection geometry (ATR-IR). AFM observations reveal that MOF nucleation occurs preferentially at the intersections of nanobelt edges and the terrace planes of adjacent nanobelts, specifically on the terrace regions immediately neighboring these reactive edges, and proceeds concurrently with localized substrate dissolution. By employing benzoic acid as a model monocarboxylic probe, we identified the formation of discrete, organic linker domains that locally suppress substrate dissolution and form nanoscale surface protrusions. Polarization-dependent ATR-IR spectroscopy demonstrates that the carboxylate groups within these domains are preferentially aligned parallel to the a -axis of Cu(OH) 2 , a configuration that is strikingly consistent with the resulting MOF nuclei. These findings indicate that heteroepitaxial growth is established by the self-organization of organic linkers into linker-oriented domains, which subsequently act as structural scaffolds to dictate the crystallographic orientation of the MOF. This study complements traditional lattice-matching considerations by highlighting the significance of interfacial molecular alignment, providing fundamental design guidelines for the fabrication of highly oriented MOF architectures.