The size effect of CoO on the selectivity of heterogeneous hydroformylation

Cobalt is undoubtedly the most promising alternative metal to rhodium for a highly active and stable hydroformylation process under mild conditions. In this study, two cobalt-based heterogeneous catalysts were synthesized via impregnating a cobalt precursor into polymers (POPs-NVP). Comprehensive characterization revealed that the cobalt species on the catalysts exist as CoO with two distinct sizes: nanoparticles and single sites. The CoO nanoparticles on POPs-NVP exhibited outstanding hydroformylation activity (81.7% yield of aldehyde and alcohol, 13.5% yield of alkane), while CoO single sites displayed robust olefin hydrogenation performance (62.6% yield of alkane, 27.3% yield of aldehyde and alcohol). These divergent catalytic behaviors were attributed to distinct electron density distributions around surface-exposed cobalt species, which were critically governed by CoO sizes on catalysts. By elucidating the size-dependent effects of CoO/POPs-NVP catalysts, this work provided insights into the complex active species states in heterogeneous cobalt-based catalysts, and established valuable experimental and theoretical foundations for designing highly efficient cobalt-based heterogeneous catalysts for hydroformylation.