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.