Metal–organic framework (MOF) thin films represent a milestone in the development of future technological breakthroughs. The processability of MOFs as films on surfaces together with their major features (i.e. tunable porosity, large internal surface area, and high crystallinity) is broadening their range of applications to areas such as gas sensing, microelectronics, photovoltaics, and membrane-based separation technologies. Despite the recent attention that MOF thin films have received, many challenges still need to be addressed for their manufacturing and integrability, especially when an industrial scale-up perspective is envisioned. In this brief review, we introduce several appealing approaches that have been developed in the last few years. First, a summary of liquid phase strategies that comprise microfluidic methods and supersaturation-driven crystallization processes is described. Then, gas phase approaches based on atomic layer deposition (ALD) are also presented.

Au-covered hollow urchin-like ZnO nanostructures were prepared with controlled size by combining nanosphere lithography (NSL), atomic layer deposition (ALD), electrodeposition, and electron beam (e-beam) evaporation. The optimal Au film thickness for sensing applications was determined by measuring the surface-enhanced Raman scattering (SERS) intensities of the substrates. Furthermore, the sensing performances of these hybrid nanostructures have been investigated by using chemical and biological molecules: thiophenol and adenine, respectively. Limits of detection (LOD) of 10⁻⁸ M and 10⁻⁶ M were found for the detection of thiophenol and adenine, respectively. Additionally, the excellent uniformity and batch-to-batch reproducibility of the substrates make them excellent candidates for reliable SERS sensing and biosensing.

In this paper, we are relating a significant improvement of the SERS effect achieved with assembled Au/ZnO nano-urchins. This improvement is realized thanks to an excellent capacity of adsorption (denoted K) for thiram molecules on these plasmonic nano-urchins, which is a key point to be taken into account for obtaining a SERS spectrum. Moreover, this outlook may be employed for different types of plasmonic substrates and for a wide number of molecules. We studied the capacity of the assembled Au/ZnO nano-urchins to be sensitive to the pesticide thiram, which adsorbs well on metals via the metal–sulfur bond. For the thiram detection, we found a limit concentration of 10 pM, a value of this capacity of adsorption (K) of 9.5 × 10${}^6$ M${}^{-1}$ and a factor of analytical enhancement equal to 1.9 × 10${}^8$.