The boiling point of ${\mathrm{D}}_2\mathrm{O}$ is greater than ${\mathrm{H}}_2\mathrm{O}$ it is because

The molecular weight of ${\mathrm{D}}_2\mathrm{O}$  is greater than ${\mathrm{H}}_2\mathrm{O}$

${\mathrm{D}}_2\mathrm{O}$ has a lower dielectric constant

${\mathrm{D}}_2\mathrm{O}$ has a lower ionic product

${\mathrm{D}}_2\mathrm{O}$ is an associated liquid