Pillared derivatives of gamma-zirconium phosphate, having the general formula ZrPO4[O2P(OH)(2)](1-x)[O-2-POH-(CH2)(n)-HOPO2](x/2). mH(2)O (n = 4, 6, 8, 10, 12, and 16), were prepared by soft topotactic reactions between colloidal dispersions of exfoliated lamellae of gamma-ZrPO4[O2P(OH)(2)]. 2H(2)O and 1,n-alkanediphosphonic acid solutions. In these compounds the interlayer distance can be easily modulated almost continuously by increasing the number of the carbon atoms in the alkyl chain, while the lateral distance of the pillars can be varied over a large interval according to the degree of pillaring. The interlayer distance of compounds with a low percentage of pillaring decreased appreciably when the intercalated solvent was eliminated (e.g., by dehydration). The reversible elongation and shortening property of the interlayer suggests that the alkyl chains, being nonrigid pillars, tend to fill up empty spaces created by the loss of interpillar solvent by adopting different conformations in the interlayer region. The large interpillar spaces filled by solvent can be seen as "tailor-made molecular vessels," in which specific reactions could be carried out in a restricted environment.