A new hybrid catalyst affording polymerization of phenylacetylene (PhA) into high-molecular-weight (M-w = 180 000) high-cis-polyphenylacetylene (PPhA) was prepared via immobilization of [Rh(cod)Cl](2) (cod = eta(4)-cycloocta-1,5-diene) on siliceous mesoporous molecular sieves MCM-41 modified by 3-aminopropyltrimethoxysilane. The polymerization was confirmed to proceed on anchored Rh-species and PPhA formed was continuously released into liquid phase, from which it was easily isolated. In comparison with related homogeneous catalysts, the hybrid catalyst provided comparable or even higher PPhA yields, considerably higher molecular weight of PPhA and reduced amounts of oligomeric by-products. The catalyst was found to be resistant to Rh leaching; however, chemical transformation of anchored Rh-species occurring during polymerization strongly reduced the possibility of catalyst re-using. (C) 2003 Elsevier Science B.V. All rights reserved.