We present here the spontaneous formation of nanoporous sheets in aqueous solution without a template to guide them, which is based on the self-assembly of dumbbell-shaped rod amphiphiles driven by a fine balance of anisotropic hydrophobic interactions, and steric constraints endowed with bulky dendritic wedges. These planar nets transform into closed 2D sheets when the rod segment increases in length. Such a unique arrangement of rigid rod building blocks might provide a new strategy for the design of nanoporous materials simultaneously with biological and electro-optical functions.