The modular structure of sepiolite is built of alternating ribbons and tunnels and results in a large internal and external surface which is decorated by various types of adsorbed H_2O molecules. A sequence of dehydration events of surface, zeolitic and coordinated H_2O has been reported. As the ribbons of sepiolite are held together by Si-O-Si linkages, the change of the interlayer spacing in response to varying H_2O content is constrained. Hence, dehydration imposes structural rearrangements within the layers themselves. The best known such rearrangement is the folding of the structure at ca. 300 °C.
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