Interfacial Microenvironment-Regulated Coordinate Structures Dictate the Metal-Organic Framework Facet Orientation toward Efficient CO Cycloaddition.

The preparation of high-quality highly oriented metal-organic framework (MOF) thin films is desirable for developing advanced functional devices. However, the pathways for controlling the oriented growth of MOFs are largely unknown, and determining their microcosmic evolution at the complex solid-liquid interface remains a challenge. Herein, we investigate the critical early growth stage of typical HKUST-1 on the COOH-functionalized Au substrate utilizing a combination of in situ surface-enhanced infrared spectroscopy, X-ray photoelectron spectroscopy, and photoinduced force microscopy. Detailed molecular level information indicates that it is not only the COOH-terminated SAM itself but also the distinct interfacial structures of the first metal coordinate layer and second ligand coordinate layer, which can be regulated in aprotic and protic solvents, that dominate the initial growth behavior of MOF and thus lead to the [111], [100], and polycrystal facet-oriented growth of HKUST-1. Moreover, the prepared HKUST-1 films exhibit a crystal facet-dependent catalytic rate in the chemical fixation of CO into cyclic carbonate. Our observations provide a reasonable guide for designing MOF-based anisotropic functional equipment.