Weak electronic correlations in the cobalt oxychalcogenide superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Na</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>CoSe</mml:mi> <mml:mn>2</m

Motivated by the newly discovered Co-based superconductor ${\mathrm{Na}}_{2}{\mathrm{CoSe}}_{2}\mathrm{O}$, we performed systematic calculations of its electronic band structures using the density functional theory plus the dynamical mean-field theory approaches. Our comparative studies reveal the weakly correlated and itinerant nature of the Co $3d$ electrons and show no sign of fluctuating local moments as expected in many other unconventional superconductors, although the Co ${e}_{g}$ orbitals are close to half filling. These suggest that ${\mathrm{Na}}_{2}{\mathrm{CoSe}}_{2}\mathrm{O}$ is a normal paramagnetic metal and its superconductivity might not be of strongly correlated nature, contrary to the initial speculation. We suggest future investigations of electron-phonon interactions to clarify its pairing mechanism.