Microporous metal-organic frameworks (MOFs) offer attributes that make them potentially compelling choices for thermoelectric applications because they combine organic character with long-range order and intrinsically low thermal conductivity. So far, thermoelectricity in this class of materials has required infiltration with external molecules to render the framework electrically conductive. Here, we present thermoelectric studies on an n-type naturally nanostructured microporous MOF, Ni₃(2,3,6,7,10,11-hexaiminotriphenylene)₂, whose pressed pellets exhibit high electrical conductivity and low thermal conductivity. The results here show that by combining the structural rigidity and high crystallinity of inorganic materials, the solution-based synthesis of organic materials, and the unique pore-based tunability and low thermal conductivity, MOFs represent an intriguing new class of thermoelectric materials.