The term intercalation denotes a process in which a molecule or an ion (guest) is placed into a host lattice. The structure of the host remains unchanged or is only slightly altered in the guest-host complex that is in the intercalation compound (intercalate).

The intercalation reaction is usually chemically or thermally reversible. Other terms like insertion, inclusion or topotactic reaction are often used for the intercalation reactions, but all of them correspondto the above given definition. Intercalation chemistry is one of the field of supramolecular chemistry. Intercalation reactions offer the way for the synthesis of new solids and allow controlled systematic changes of their physical properties. These materials have many applications, for instance as catalysts, sorbents, electrochromic displays, electrodes for secondary batteries (Li-ion batteries) and components for fuel cells.

Our team has a long-lasting experience in the study of the intercalation into vanadyl phosphate (VOPO₄) and isostructural compounds and into layered double hydroxides. We investigated intercalation of organic compounds with oxygen as a donor atom into VOPO₄ and organic acids into layered double hydroxides. With the help of powder X-ray diffraction, vibrational spectroscopy and molecular modeling we proposed the arrangement of the guest molecules in the structure of prepared complexes.

In our work, we are looking for new compounds which can serve as host materials. In this effort, we focused on functionalized layered organophosphonates which can be applied as catalysts, ion exchangers, sorbents and in molecular recognition. We prepare new inorganic-organic hybrid materials, namely arylphosphonates and alkylphosphonates of metals. Especially proton conductive organophosphonates in which the organic part is functionalized with carboxyl or sulfonic groups are considered as prospective materials as they can be applied as membranes in fuel cells.

For the characterization of the prepared compounds and the study of their chemical and physical properties the following diagnostics are used: powder X-ray diffraction, single-crystal X-ray diffraction, thermogravimetric analysis, infrared and Raman spectroscopy, energy-dispersive X-ray analysis, differential thermal analysis, ac and dc conductivity and solid-state NMR. For the study of interconversions of arylphosphonates of alkaline-earth metals we developed a method of computer-controlled additions of reagents to phosphonate suspensions using an automated burette.

We solve the structure of the prepared phosphonates from the powder X-ray data. For this purpose we use FULLPROF and FOX programs. We succeeded in the determination of structure of several 4‑carboxyphenylphosphonates of alkaline-earth metals. As an example, the structure of Ca(HOOCC₆H₄PO₃H)₂ is shown here.

We also solved structures of several phosphonates by single-crystal X-ray diffraction, when suitable crystal were prepared, for instance a structure of copper 4-carboxyphenylphosphonate, whose gibbsite‑like layer is depicted below.