The preparation of organic-inorganic materials based on the topotactic exchange reactions of the gamma phase of zirconium phosphate and polyphenyl bisphosphonates is reported. The treatment of these materials with hypophosphoric, phosphorous and methylphosphonic acids easily led to an isomerization of the gamma phases to their alpha allotropes. These reactions rendered finely engineered supramolecular structures by means of mild, simple processes performed in the solid-liquid interface. This kind of clean gamma-to-alpha transformations described in our work has few precedents in the literature and allows for the effortless preparation of libraries of similar materials in which the testing of a given set of properties versus subtle structural changes may be easily performed. Using this rationale we have produced materials able to store up to 1.7% (w/w) of H-2 at 77K and 1 atm with such high ultramicroporosity that the DOE-goal H-2 densities established for 2010 could be complied at pressures well below 5 atm. (C) 2010 Elsevier B.V. All rights reserved.