In this work, we studied the properties of thin nanoporous carbon coatings on very thick porous silicon (PS) layers of very high porosity. The PS was obtained by etching pores into crystalline Si wafers in a process controlled to prevent crack formation during etching and drying. The nanoporous carbon was made by dipping the PS samples in diluted polyvinyl alcohol and submitting the coating to pyrolysis at different temperatures (in the 513-843 K range). The porous carbon coatings obtained on porous silicon using this method presented good adherence, uniform thickness and good optical transparency, the greatest luminescence intensity being obtained at a pyrolysis temperature of 513 K. Such a composite nanoporous structure of two type IV materials may find a large number of future applications, ranging from luminescent devices to molecular sieves.