A new hydrogen bonded network self-assembles under mild conditions from benzene-1,3,5-triyl tris(butyl carbamate) or benzene-1,3,5-triyl tris(hexyl carbamate). One of the carbonyl groups in the tri-carbamate does not form a CO⋯H–N hydrogen bond in the sheet-like structure. Although the building blocks only differ in the carbon numbers of the side chains, this 2D unsaturated hydrogen bonded network is different from the saturated one self-assembled from benzene-1,3,5-triyl tris(propyl carbamate). The lamellar structures were studied and compared by using their melting points, NMR and FT-IR spectroscopy, and single crystal X-ray diffraction.