H2F may, possibly, abbreviatedly stand for 7,8-dihydrofolate (*), also called dihydrofolate or dihydrofolic acid; for which compound, DHF (**) is also, and more commonly, used as abbreviation. If so; it is not properly called a 'material', at least in the strict sense of the word.
(*) Karl M. Kadish, Kevin M. Smith, Roger Guilard (Eds.), "The Porphyrin Handbook", Vol. 4: "Biochemistry and Binding: Activation of Small Molecules", Academic Press, 2000, p. 314.