The preparation of ordered mesoporous boron nitride (BN) by using trimethylaminoborazine as a BN source and mesoporous carbon CMK-3 as a template is reported. X-ray diffraction, transmission electron microscopy, and pore size analysis show that the structure of the synthesized BN molecular sieves consists of a two-dimensional regular array of uniform mesopores approximately 4.4 nm in diameter (see Figure).