Since 1992, Gérard Férey has devoted the last part of his scientific career to the genesis, the structures, some mechanisms of formation, as well as the properties and applications of porous solids, either with an inorganic or a hybrid organic-inorganic framework, in order to reach rationally ‘tailor-made’ materials, through an integrated strategy.
More than 150 new structural types resulted from this approach, with useful pore dimensions ranging from 8 to 50 Å. A careful choice of the metals of the precursors made that most of them are thermally stable (up to 600°C) and resistant to humidity, two criteria needed for eventual applications coupled with reactions performed in water.
Based on the concept of secondary building units (SBU), the elucidation of their mechanism of formation used many complementary in situ techniques (NMR, diffraction, EXAFS...) for following the steps of the reaction within autoclaves (ca. 200°C, autogenous pressure).
Whatever the nature of the framework (inorganic or hybrid), the time-resolved identification of the reactive species (strongly dependent on pH) shed some light on the formation of the solid from the solution. The main hitherto unknown result was to show that the polynuclear SBU units, which describe the final solid, already exist in the solution before precipitation, after one or several identified steps.
From the observed invariance of these SBU, an original computer simulation of their 3D associations was successfully performed for predicting the various possible structures based on these SBU.
This even now unique strategy led to predict the first crystallized mesoporous solids MIL-100 and -101 before their ‘tailor made’ isolation. This pioneer approach was particularly successful for metal-organic frameworks (MOFs) (Férey was one of its few pioneers) and where he showed the richness of this family. In particular, he showed that a lot of metals, with various oxidation states, can be incorporated after a much more difficult chemistry in the framework, for introducing for the fisrt time physical properties, usually encountered in dense phases.