  Kitaev's honeycomb lattice spin model is a remarkable exactly solvable model,
which has a particular type of spin liquid (Kitaev spin liquid) as the ground
state. Although its possible realization in iridates and $\alpha$-RuCl$_3$ has
been vigorously discussed recently, these materials have substantial non-Kitaev
direct exchange interactions and do not have a spin liquid ground state. We
propose metal-organic frameworks (MOFs) with Ru$^{3+}$ (or Os$^{3+}$) forming
the honeycomb lattice as promising candidates for a more ideal realization of
Kitaev-type spin models where the direct exchange interaction is strongly
suppressed. The great flexibility of MOFs allows generalization to other
three-dimensional lattices, for potential realization of a variety of spin
liquids such as a Weyl spin liquid.
