The development of earth-abundant catalysts with high activity and selectivity is important yet challenging in hydroformylation. In this work, a stable and efficient phosphine-oxide group containing porous organic polymer was afforded, which served as a ligand and a support to fabricate a heterogeneous Co catalyst (Co/POL-POPh3) for hydroformylation of 2-octene under mild condition. A 2-octene conversion of 94.6 % and at least three recycles were achieved using Co/POL-POPh3 in the hydroformylation with a 51.1 % aldehyde selectivity under 423 K and 3.0 MPa. The experimental and characterization results elucidated that the highly dispersed Co ions was coordinated with the phosphine-oxide groups in the polymer, which was beneficial for the 2-octene isomerization and in turn led to the excellent performance for synthesis of oxygenates. Furthermore, a reaction mechanism was also suggested for 2-octene hydroformylation over the Co/POL-POPh3 catalyst. The current study delivers valuable insights into the adjustment of the catalytic efficiency of non-previous metal catalysts in the heterogeneous hydroformylation of internal olefins.