The Fe3+ lattice in the Bi2Fe4O9 was found (in an ILL experiment) to materialize the first analogue of a magnetic pentagonal lattice, namely the so called Cairo pentagonal lattice. Our very recently obtained polarized Raman spectra of Bi2Fe4O9 under hydrostatic pressure (up to 7.5 GPa, applied at 300 K) provide indications for significant structural transformations, suggesting that a structural transition takes place at about 4-5 GPa and it is reversible upon cycling the pressure.The proposed experiment is aimed at the temperature and pressure evolution of the crystal structure parameters Bi2Fe4O9 and the consequences on its original magnetic structure.