Physical vapor deposition of an oriented metal–organic framework HKUST-1 thin film on an insulating substrate

Abstract

HKUST-1 ([Cu₃(BTC)₂], BTC = 1,3,5-benzenetricarboxylate) is a promising metal–organic framework (MOF) for device applications because its properties, such as electrical and ionic conductivity, can be controlled through the introduction of guest molecules into its pores. Synthesizing oriented films on an insulating substrate using physical vapor deposition (PVD) is critical for device applications and interface studies of HKUST-1. However, substrates for the synthesis of oriented HKUST-1 films via PVD are currently limited to metals. Here, we report the synthesis of a (111)-oriented HKUST-1 film on an insulating glass substrate using a combination of PVD and solvent vapor annealing. Annealing the precursor films with acetic acid vapor successfully promotes the diffusion and reaction of the precursors, producing a (111)-oriented HKUST-1 thin film. Furthermore, this method provides thin films of other three-dimensional MOFs, such as UiO-66 ([Zr₆(OH)₄O₄(BDC)₆], BDC = 1,4-benzenedicarboxylate) and its analog UiO-66-(OH)₂. This study demonstrates that PVD combined with solvent vapor annealing is a promising method for synthesizing oriented MOF films on an insulating substrate, thereby advancing interface research and the development of stacked-film devices using MOFs and various functional materials.