Ce(III)-MOFs with 1D chain architectures and their derivatives as earth-abundant electrocatalysts for the acidic oxygen evolution reaction.

Cerium(III)-based metal-organic frameworks (Ce-MOFs) with one-dimensional chain secondary building units were synthesised and evaluated as oxygen evolution reaction (OER) electrocatalysts in acid. The MOFs act as pre-catalysts, transforming in-situ into active cerium oxide species. The best pristine MOF material that employs 1,3,5-triazine-2,4,6-triyl)tris(thiophene-2-carboxylate linkers (H3TTT), shows higher intrinsic activity and stability than commercial CeO2. The results highlight the role of linker chemistry. Pyrolysis at 800°C generates conductive CeO2-carbon composites with strong cerium anchoring and high sp2-carbon content. The thiophene-based MOF uniquely yields Ce2S3 and bulk defective CeO2-x phases via in-situ sulfurisation. The derived materials exhibit lower overpotentials, smaller Tafel slopes, and improved durability, with Ce-TTT-derived material exhibiting a Tafel slope of 56 mV dec-1 and displaying stable activity after 1,000 CV cycles in 0.5 M H2SO4. These results identify Ce-MOFs as effective templates for an earth-abundant OER catalysts and highlight pyrolytic carbon matrices and phase evolution as key design parameters.