Isomerization and redox tuning in ‘Maya yellow’ hybrids from flavonoid dyes plus palygorskite and kaolinite clays

•Organic–inorganic hybrid materials from kaolinite and palygorskite clays and flavonoid natural dyes are prepared.•The composition of the organic fraction is studied by solid state electrochemistry and mass spectroscopy.•Thermal treatment above 100 °C determines significant isomerization and oxidation reactions.•Dye attachment to the clays would define a peculiar ‘Maya chemistry’.

The composition of the organic fraction of organic–inorganic hybrid materials prepared upon attachment of different natural, ‘historical’ flavonoid yellow dyes (zacatlaxcalli, fustic, marigold and cosmos) to palygorskite and kaolinite clays is described. Upon thermal treatment between 100 and 180 °C, significant isomerization and oxidation reactions occur thus resulting in the formation of polyfunctional materials potentially usable for therapeutic, catalytic and art purposes. The dye attachment to the clays would define a ‘Maya chemistry’ whose complexity could explain the versatile use of such materials in the pre-Columbian cultures.

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