The invention relates to a membrane filter (1) comprising a moulded body (2) for separating substance mixtures, especially gas mixtures (5) of different molar masses, and to a method for producing such a membrane filter (1). By providing the membrane filter (1) with a cement-bound porous material, especially micro-concrete, as an essential material component having a rock graining with a small particle size, a membrane filter is created, combining low production costs, a good mechanical loadability, and a good temperature resistance. The pore size can be approximately randomly adjusted at a low cost during the production.