The inert surface of graphitic boron nitride sheet (g-BN) hinders the application of this new nanomaterial in electronic devices. Herein, we exploited the possibilities of functionalizing g-BN by introducing Al-dopant and defects (Stone-Wales or vacancy), and studied the interactions between the modified g-BN and CO molecule. The doped and defective g-BN exhibit much higher affinities with the probe molecule than pristine g-BN. The vacancy-defected g-BN shows narrower band gap and spontaneous magnetization upon CO adsorption. These results may help to seek appropriate chemical modification methods to widen the application fields of the g-BN nanomaterials. (C) 2009 Published by Elsevier B. V.