Liquid-phase epitaxy of metal organic framework thin films

Metal-organic framework (MOF) thin films are multilayer materials ranging from nanometers to micrometers in thickness, physically or chemically adhesive to a (functionalized) substrate and, in an ideal case, exhibiting low roughness and high homogeneity. Various innovative approaches have been developed for MOF thin film fabrication. Among these advanced materials, surface-attached metal-organic frameworks (SURMOFs) are an important class of MOF films. SURMOFs, fabricated in a step-by-step liquid phase epitaxial (LPE) fashion by alternating deposition of metal and organic linker precursors on a functionalized substrate, for example, thiolate-based self-assembled monolayers (SAMs), have already exhibited their utility in both research and potential applications. SURMOFs combine surface science and the chemistry of MOFs, possessing the following unique advantages that cannot be accessed through other methods: (i) precisely controlling thickness, roughness and homogeneity as well as growth orientation, (ii) studying of MOF growth mechanism, (iii) modifying/tailoring MOFs' structures during the SURMOF growth and thus creating customizable properties, and (iv) existing in the form of thin film/membrane for direct applications, for example, as sensors. This review discusses the oriented and crystalline SURMOFs fabricated by LPE approach, covering their preparation, growth mechanism, and characterization methodology as well as applications based upon the most newly updated knowledge.