In the present paper, a facile and cost effective method was developed to fabricate micrometer-sized hollow polyurea microcapsule via W/O emulsion, with the inorganic metal salts as encapsulated materials. The size of porosities and non-porous parts were uniform with diameter ranging from 20 to 40 mn for both interior and exterior surfaces. The immobilized nickel nanoparticle was well dispersed with diameter under 30 nm. Polyurea hollow microcapsules encapsulated with NiCl2 presented better thermal stability than polyurea itself. The immobilization of NiCl2, was rather effective, and no leaching could be observed under ethanol, toluene and water at 110 degrees C while stirring for 5 h. This heterogeneous microcapsule with NiCl2 could be reused for benzaldehyde reduction with no loss of activity or selectivity, meaning that it is an effective immobilization method. (c) 2005 Elsevier B.V. All rights reserved.