Literature about vivianite -In Frisenda et al., 2020, we can find discussed the naturally occurring van der Waals materials. Among the phosphates, Frisenda and coworkers described the vivianite as "a hydrated iron phosphate with an approximate formula Fe 2+ Fe2 2+( PO4)2•8H2O. Vivianite is known to be sensitive to visible light exposure which leads to a marked change in its color from colorless/pale green to dark green/brown. Bulk vivianite has been used as natural electron donor to effectively dechlorinate a variety of chlorinated organics, the principal and most frequently found contaminants in soil and groundwater that generates significant environmental problems". Frisenda and coworkers also provide references about the band gap of vivianite as "an indirect band gap in the range of ~3.3-4.6 eV and a paramagnetic ground state" .