A layered borate Na₂B₁₀O₁₇·H₂en (1, en = ethylenediamine) with three-dimensional microporosity within the layers has been synthesized under solvothermal conditions by using organic amines and inorganic cations as the templates. Its framework displays a unique 5-connected net constructed by B₅O₁₁ cluster and emits blue luminescence.