Halliday & Matthiessen (2014: 425):
We noted above that prepositional phrases serve either as Adjunct or as Postmodifier. The exception is prepositional phrases with of, which normally occur only as Postmodifier; the reason is that they are not typical prepositional phrases, because in most of its contexts of use of is functioning not as minor Process/Predicator but rather as a structure marker in the nominal group (cf. to as a structure marker in the verbal group).
Hence of phrases occur as clause elements only in two cases:
(1) as circumstance of Matter, e.g. Of George Washington it is said that he never told a lie,
(2) as one of a cluster of circumstances expressing a sense of ‘source’, all ultimately deriving from abstract locative ‘from’: died/was cured of cancer, accused/convicted/acquitted of murder, and so on.