Sulfur integration in nanostructures boosts catalytic efficiency in hydrogenation reactions

Despite natural evidence indicating the importance and efficiency of sulfur as a catalyst for critical redox reactions, including hydrogenation (addition of hydrogen to molecule) and dehydrogenation (its opposite), chemists have struggled to manage the complexity and fragility of the enzyme on a large scale.

Now, researchers from the Northwestern University have developed a new approach to integrate metal-sulfur active sites into metal-organic frames or MOFs. MOF containing sulfur have significantly outperformed their non-soufre counterparts in the hydrogenation catalysis, opening the way to more accessible methods to study the active sites they create.

“Acceleration of catalysis is essential to increase efficiency, reduce energy consumption and minimize environmental impact, because faster reactions lead to higher yields in a shorter period,” said Omar K. Farha, expert from the Northwestern MOF and co-ordering. “MOFs are an excellent platform to study and optimize catalysts.”

The study, published today in the journal Nature chemistrySupports existing MOF applications in gas storage, carbon capture, drug delivery and water purification, and uses the unique structural properties of MOFs and the high surface area to accelerate catalysis.

“There was almost no example of well -defined metallic sulfide sites in porous frames like MOF,” said the first author Haomiao Xie, who led study experiment in Northwestern. “This study fills its differences by introducing a new method to install active sites based on sulfur in MOF without compromising their structure, opening a path to create enzymatic models in stable materials.”

MOFs are porous and crystalline materials of the size of nano -tail which are structured to create a large area and are designed with pores to capture gases, vapors and other agents – similar to the way a sponge captures water.

“We consider this as a generalizable approach to reproduce the characteristics of metal-sulfur sites in stable and solid materials, take up a long-standing challenge in the field,” said Farha. “The study provides the scientific community with a new powerful strategy to design and study metal-sulfur catalysts in a wide range of frames for a range of applications.”

Farha, professor of chemistry at the Weinberg College of Arts and Sciences, is a member of the Northwestern Paula M. Triens.

To assess the effectiveness of their solution into several stages (which chemically converted metal chloride bonds into metal-hydroxide, then in metal sulfide), the team used advanced structural and spectroscopic tools to confirm the frame and analysis of the diffraction of electrons. The team has combined experimental and calculation information to show that hydrogen has enabled Sulphur to activate more efficiently – a key to improved MOF catalytic performance.

“The study shows how sulfur ligands fundamentally change the responsiveness of metallic sites, which could be largely useful in the entire catalysis,” said Laura Gagliardi, author of co-corners and professor of chemistry and molecular genius at the University of Chicago. “The density functional theory calculations discover how sulfur ligands improve reactivity and lower energy barriers for the activation of hydrogen.”

Because the chemists have tested the approach on two families of MOF, they plan to advance research by trying to install similar sites in additional families that have different structural properties. From there, they can experiment with more complex model reactions and widen the scope of hydrogenation reactivity to measure its effect on more difficult substrates.