Titanium dioxide (TiO₂) is one of the most successful photocatalysts due to its high efficiency, stability, abundance, and low toxicity. Titanium-based metal–organic frameworks (Ti-MOFs) are considered very appealing subclass of MOFs due to the possibility of combining Ti⁴⁺ electro/photoactivity, high surface area, crystallinity, good photostability and high chemical diversity.
The integration of Ti-MOFs in electrochemical and optoelectronic applications and devices can benefit from the processing of MOFs as homogeneous films. This would for example, ease the assessment of their performance by direct electrochemical and photoelectrochemical analysis. Compared to other MOFs, thin film integration is even more demanding in the case of Ti-MOFs due to its challenging synthesis (Ti-MOFs are still rather scarce comparing to other metals MOFs).
With this goal in mind, we will describe two different approaches to tackle this problem (Figure 1). First, we will introduce the use of amphiphilic modulators to produce Ti-nanoMOFs (70 nm) with improved colloid stability for their processing as thin films with porosities near to the pristine framework. Next, we will introduce an alternative approach towards thin film formation that makes use of the metal-induced topological transformations recently reported by our team. During this process an heterometallic Ti-MOF film is converted into another Ti-MOF with different topology by controlled exposition to solutions containing a third metal. Our results suggest that this route is compatible with the fabrication of thin films of heterometallic frameworks, that are not accessible to other more conventional methods and open the door for the exploitation of mixed-metal chemistry in applications reliant on a solid support.

<b>Figure 1 </b>Different approaches for the processing of titanium MOFs as thin films a) Spin-coating of Ti-nanoMOFs and b) on surface metal-induced topological transformation by vapor-assisted conversion method

Figure 1 Different approaches for the processing of titanium MOFs as thin films a) Spin-coating of Ti-nanoMOFs and b) on surface metal-induced topological transformation by vapor-assisted conversion method

Prof Carlos Marti-Gastaldo

Associate Professor, Universidad de Valencia, ICMol

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