The present invention concerns a polyphase particulate composite material containing a microporous phase which is essentially carbon whose microporous volume is between 0.1 cm.sup.3 /g and 1 cm.sup.3 /g, which is associated with an amorphous mineral dispersed phase essentially consisting of an oxide of silicon, aluminum, titanium or magnesium disposed on the carbon phase, at a thickness of less than 10 nm. The invention is also concerned with a process for the preparation of these composite materials, and the use thereof as a molecular sieve.