Films of few-layers defective N-doped or undoped graphene (10-15 nm) containing antimony oxide nanoparticles (15-30 nm) have been prepared on quartz by pyrolysis of alginate or chitosan adsorbing Sb(OAc)(3). XPS shows that the prevalent Sb oxidation state is +III, while thermoprogrammed CO2 desorption shows that these films exhibit basic sites. These thin films have used as basic catalysts to promote the Michael addition of active methylene compounds and the Henry condensation. These results have been rationalized by DFT calculations that have shown that undercoordinated or two-fold coordinated oxygen atoms on SbOx clusters can act as basic sites, providing a wide range of basic strength. (c) 2020 Elsevier Inc. All rights reserved.