Is there a name for the use of sunlight in metabolic processes?
Photometabolism or photocatalysis would be apt terms and the former would specifically refer to biochemical reactions.

Photometabolism is also used in the context of the light dependent conversion of 7-dehydrocholesterol to Vitamin-D. 

A google scholar search with photometabolism returns many peer-reviewed articles that have used this term. Some examples:


Photometabolism of 7-dehydrocholesterol to previtamin D3 in skin.
The photometabolism of glucose by an hydrogen-adapted alga
Photometabolism of Heterocyclic Aromatic Compounds by Rhodopseudomonas palustris OU 11.