In-situ transformation of a conjugated nickel-organic framework into active nickel oxyhydroxide for electrocatalytic 5-hydroxymethylfurfural oxidation.

Utilizing electrical energy for the targeted conversion of biomass into valuable molecules is a crucial building block for a future circular economy. Herein, a Nickel (Ni)-based conjugated metal-organic framework (MOF) having salicylaldehydate linkages (1, 3, 5-triformylphloroglucinol: Tp) was synthesized via a solid-state process. The resulting 2D framework (Ni-Tp) demonstrates a highly selective electrocatalytic conversion of 5-hydroxymethylfural (HMF) to 2, 5-furandicarboxylic acid (FDCA) with excellent faradaic efficiency (96 ± 4 %). In-situ Raman and X-ray absorption spectroscopy (XAS) reveal that Ni-Tp acts as a precatalyst for uniformly dispersed nickel (oxy)hydroxide (NiOOH) in the electrocatalytic organic oxidation reaction (OOR) process. The combination of efficient electron transport of the Ni-Tp and the uniform dispersion of newly formed nickel (oxy)hydroxide with excellent electrolyte availability leads to redox (and potentially catalytic) activity of all in situ formed nickel sites. Thus, the Ni-Tp is an ideal precatalyst in terms of nickel (oxy)hydroxide active site exposure. This work demonstrates a cost-effective method for synthesizing efficient MOF-based electrocatalysts for a relevant catalytic reaction.