He'll keep his pledge to donate 10,000 mosquito nets to charity to help fight Malaria in Africa
I would analyse this sentence as follows:
Verbs = will keep
direct object= his pledge to donate 10,000 mosquito nets (It's the direct object because it answers the question: will keep what?).
Adverbial/ adjunct of purpose = to help fight Malaria in Africa.(this clause is an adverbial/adjunct because it states why he is keeping his pledge to donate the nets.
The adverbial adjunct refers to the verb phrase will keep his pledge because it says why he keeps the pledge.( the purpose of keeping the pledge).