When CO is heated with $\mathrm{NaOH}$ under pressure. we get:

Sodium formate is created when sodium hydroxide and carbon monoxide combine. 

This reaction occurs at pressure and temperature ${120}^{\circ }\mathrm{C}-{200}^0\mathrm{C}$ and in the presence of a catalyst. $\mathrm{CO}+\mathrm{NaOH}\to \mathrm{HCOONa}$