Scalable Synthesis of Highly Efficient and Thermostable Graphitic Carbon Nitride for White Light-Emitting Diodes

White light-emitting diode (WLED) lighting technology is critical for reducing global energy consumption. The commercial WLED relies on rare-earth-activated inorganic phosphors, which require energy-intensive synthesis and face rare-earth resource scarcity. Here, we present a low-cost, large-scale synthesized graphitic carbon nitride (g-CN) phosphor that achieves near-unity photoluminescence quantum yield (PLQY) and exceptional thermostability. Through molecular donor–acceptor engineering, we control the molecular energy levels, modulating emission from blue to orange color, and enhance molecular rigidity, suppressing non-radiative decay and boosting PLQY from 8 to 98%. The material retains 92% of room-temperature PL intensity at 150 °C and 83% of initial PL intensity after 1000 h of thermal aging. The g-CN phosphor-based WLEDs exhibit standard white light with a peak power efficiency of 140 lm W –1 and a maximum external quantum efficiency of 37%. Our work synchronously unlocks tunable emission, suppressed non-radiative decay, and unprecedented thermostability, a triad previously unattained in organic materials.