The　excited　state　acidity　of　ESPT　molecules　is　first　demonstrated　as　a　suitable　means　of　catalysis　for　the　light-regulated　ring-opening　polymerization　of　lactones,　in　combination　with　a　photosensitizer　as　the　energy-transfer　cocatalyst　to　harness　light.　Under　blue　light　irradiation,　this　method　could　afford　metal-free　polyesters　with　well-controlled　molecular　weights　and　narrow　dispersities.