Heterometallic or mixed-metal Metal-Organic Frameworks (MOFs), incorporating two or more metal ions to the inorganic node of the frameworks, are increasingly gaining importance as a route to produce materials with increasing chemical and functional complexity. Heterometallic MOFs can offer important advantages over their homometallic counterparts to enable targeted modification of the adsorption properties, structural response, electronic structures, or chemical reactivity of the framework. Our group recently reported the synthesis of the new family of heterometallic Ti-MUV-101(M) (MUV = Materials of Universidad de Valencia). We use these materials to exemplify the advantages of controlling metal distribution across the framework in heterogeneous catalysis by exploring their activity toward the degradation of a nerve agent simulant of Sarin gas. By using an integrative experimental/computational approach we answer one of the key open questions in the area of mixed-metal MOFs: How can the metals in the inorganic node influence each other for tuning the performance of the material?<br/>MUV-101(Fe) is the only pristine MOF capable of catalytic degradation of diisopropyl fluorophosphate (DIFP) without the presence of a basic/nucleophilic co-catalyst. This is a remarkable result in comparison with the Zr(IV)-MOFs currently dominating the area. The catalytic activity of MUV-101(Fe) cannot be explained only by the association of these two metals but to their synergistic cooperation to create a whole that is more efficient than the simple sum of its parts. Our simulations suggest that the synergetic cooperation of Ti(IV) Lewis acid and Fe(III)-OH Brönsted base sites in this dual metal catalyst leads to a much lower energy barrier for more efficient degradation of DIFP in absence of a base. Overall, this mechanism resembles the activity of the metalloenzyme purple acid phosphatase that displays also bimetallic Fe(III)-M(II) active sites.<br/>To the best of our knowledge this is the first example of a dual metal transition state in heterometallic MOFs that enables clear understanding of the individual roles played by the metals combined and their mutual cooperation. We are confident our results represent an excellent platform to guide the design of other heterometallic frameworks and span the interest of this family of MOFs to a broad scope of cascade or tandem reactions in which synergetic catalysis might yield unprecedented boosts in performance.

Heterometallic titanium-organic frameworks as dual-metal catalysts for synergistic hydrolysis of nerve agent simulants

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.