Phosphonic acids R-PO₃H₂ are powerful tools for the design of new generations of Organic-Inorganic Hybrid Materials. By reaction with divalent metal salts in solution, original structures (i. e. metal phosphonates) can be prepared, in which the structural, physical and chemical properties are directly induced by the choice of the R radical bound to phosphorus, (i)- If a functionalized phosphonic acid is used, Z-R’-PO₃H₂ (Z = functional group), original pillared layered structures (Z = CO₂H) or zeolite-like arrangements (Z = NH₂) can be produced, in which the functional end Z participate to the cohesion of the hybrid network. (ii)- The specific properties of an organic molecule can be transferred to a phosphonate hybrid solid, simply through a functionalization of this molecule by PO₃H₂ ends, that are subsequently reacted with metal salts to encapsulate the organic centre within the phosphonate framework. This is for example the case for metalloporphyrinic phosphonic acids, that lead to supported oxidation catalysts the specific area and porosity of which (and consequently catalytic performances) are closely related to the length and rigidity of the spacer between the porphyrin macrocycle and the PO₃H₂ groups.