Preheat oven to 350 degrees. Spread 1 cup each chopped pecans and shredded sweetened coconut on baking sheet; bake until golden, 5 minutes. Cool; toss with 1 cup semisweet chocolate chips.
Line a 10-by-15-inch rimmed baking sheet with foil. Break 12 graham crackers in half; fit in pan in single layer.
In saucepan, whisk 12 tablespoons unsalted butter and 1/2 cup light-brown sugar over medium until smooth; spread over crackers.
Bake until bubbly, 10 minutes. Sprinkle with nut topping; press gently. Cool; break into pieces.