Layered organic-inorganic hybrids of semiconductive MoO3 with organic components, polypyrrole, polyaniline, and 5,10,15,20-tetrakis(N-methyl-4-pyridino)porphyrin), have been investigated for VOCs, specifically aldehyde gases, sensing properties by means of monitoring their electrical resistance. Among the various organic/MoO3 hybrids investigated, the sensitiveness of organic/MoO3 hybrids to aldehyde gases is found to be dominated by interlayer spaces for VOC accommodation. (c) 2008 Elsevier B.V. All rights reserved.