Thylakoids, photosynthetic sub-cellular plant structures, have been entrapped within silica network using the sol-gel process. The photocatalytic splitting of HO into O by these structures has been studied using a Clark cell reactor. The influence of the silica precursor concentration on the chemical, morphological and diffusion properties of the matrix have been investigated and correlated with the enzymatic activity of entrapped thylakoids. Compared to the free thylakoid suspension, the bioactivity of entrapped thylakoids can be extended during several weeks. The addition of stabilizing agents (i.e. glycerol and bovine serum albumin) does not essentially improve the oxygen production. This work clearly demonstrates that through the immobilization of photosynthetic membranes, photocatalytic reactors capable of biomimicking photosynthetic processes, such as harvesting solar energy and splitting water molecules, can easily be targeted.