Traced functional groups in the FT-IR spectrum of sample S1.

Traced functional group	Wave no.
MgO6 octahedral	427 cm−1
Mg–O bending	551 cm−1
MgO6 octahedral	777 cm−1
Si–O bending	895 cm−1
Si–O stretching	953 cm−1
Si–O–Si	1095 cm−1
Surface OH bending	1633 cm−1
Surface OH stretching	3435 cm−1