Abstract: A molecular sieve material is combined with a porous carrier material. The pores of the molecular sieve material are impermeable to molecules or organisms having a size equal to or greater than that of the water molecule either because the molecular sieve material is selected so as to have pores which are smaller than such molecule or because the pores of the molecular sieve material are closed by a film. The pores of the molecular sieve material thus remain unoccupied and are able to exert an attractive force on molecules or organisms which are to be captured. The pores of the carrier material are designed to accept molecules or organisms having a size equal to or greater than that of the water molecule so that, when such molecules or organisms are attracted by the molecular sieve material, they can be trapped in the carrier material.