Tunable metal hydroxide-organic frameworks for catalysing oxygen evolution

The oxygen evolution reaction is central to making chemicals and energy carriers using electrons. Metal hydroxide-organic frameworks are shown to act as a tunable catalytic platform for oxygen evolution, with pi-pi interactions dictating stability and transition metals modulating activity. The oxygen evolution reaction is central to making chemicals and energy carriers using electrons. Combining the great tunability of enzymatic systems with known oxide-based catalysts can create breakthrough opportunities to achieve both high activity and stability. Here we report a series of metal hydroxide-organic frameworks (MHOFs) synthesized by transforming layered hydroxides into two-dimensional sheets crosslinked using aromatic carboxylate linkers. MHOFs act as a tunable catalytic platform for the oxygen evolution reaction, where the pi-pi interactions between adjacent stacked linkers dictate stability, while the nature of transition metals in the hydroxides modulates catalytic activity. Substituting Ni-based MHOFs with acidic cations or electron-withdrawing linkers enhances oxygen evolution reaction activity by over three orders of magnitude per metal site, with Fe substitution achieving a mass activity of 80 A g(catalyst)(-1) at 0.3 V overpotential for 20 h. Density functional theory calculations correlate the enhanced oxygen evolution reaction activity with the MHOF-based modulation of Ni redox and the optimized binding of oxygenated intermediates.

Automated summary

The oxygen evolution reaction plays a central role in the production of chemicals and energy carriers using electrons. Metal hydroxide-organic frameworks have been demonstrated to be a tunable catalytic platform for this reaction, with stability being dictated by π-π interactions and activity being modulated by transition metals. By combining the high tunability of enzymatic systems with known oxide-based catalysts, it is possible to achieve both high activity and stability. This study reports on the synthesis of metal hydroxide-organic frameworks that act as a tunable catalytic platform for the oxygen evolution reaction, with stability being determined by π-π interactions between adjacent stacked linkers and catalytic activity being influenced by the nature of transition metals in the hydroxides. Substituting Ni-based metal hydroxide-organic frameworks with acidic cations or electron-withdrawing linkers significantly enhances the activity of the oxygen evolution reaction, with Fe substitution achieving a mass activity of 80 A g(catalyst)(-1) at 0.3 V overpotential for 20 hours. Density functional theory calculations correlate the enhanced activity with the modulation of Ni redox and the optimized binding of oxygenated intermediates by the metal hydroxide-organic frameworks.