The synthesis of mesoporous boron nitride, using an aminoborazine as the boron nitride source, with silica (SBA-15) or mesoporous carbon (CMK-3) as the template is compared. Tri(methylamino)borazine (MAB) is converted to BN inside the mesopores of silica or carbon molecular sieves through a mild thermal process. Boron nitride is obtained after the removal of the hard template using an ammonia thermal treatment (carbon template) or an HF treatment (silica template). X-Ray diffraction, TEM and pore size analysis show that the structure of the BN molecular sieves synthesized from the carbon template consisted of a 2D regular array of uniform mesopores 3.4 nm in diameter. The hydrophilic nature of the silica template prevents successful pore filling with the aminoborazine precursor. Ordered BN molecular sieves are obtained at 1000 °C with a specific surface area of 500 m² g⁻¹ using mesoporous carbon molecular sieves as a hard-template.