Here are a some picture book ideas:
Just a Dream by Chris Van Allsburg
The Wump World by Bill Peet
The Lorax by Dr. Seuss
Many nonfiction books and articles (something from
Time For Kids for example) are written to persuade the reader to: conserve energy, get involved in saving endangered species, to exercise and make healthy food choices, etc.
I've used the books the pp mentioned
I Wanna an Iguana by Karen Kaufman
Dear Mrs. LaRue: Letters from Obedience School by Mark Teague
to teach persuasive writing which . . . would of course tie into teaching author's purpose in reading.