Rosin‑derived carbon dots with dual‑rigid confinement: A scalable, biomass‑based route to sunlight‑excitable RTP materials for harsh conditions

Developing multifunctional room-temperature phosphorescent (RTP) materials that can be excited by sustainable sunlight, withstand extreme environments (high temperature, acid, alkali), and are derived from renewable biomass is highly attractive for the circular bioeconomy. Here, we report a one‑step, scalable calcination approach to convert rosin - an abundant forestry residue - into a CDs@MS/Al 2 O 3 composite, where rosin‑based carbon dots (CDs) are in situ embedded within a dual‑rigid mesoporous silica‑alumina matrix. Unlike conventional inorganic phosphors that rely on costly and toxic rare‑earth elements, our composite, which uses a biomass-derived carbon source, exhibits bright green RTP under both 365 nm UV and natural sunlight, with a lifetime of 1.66 s and a quantum yield of 13%. The material retains strong phosphorescence after exposure to acidic, alkaline, high‑salinity, and extreme temperature conditions. Mechanistically, the rigid network suppresses non‑radiative decay via spatial confinement and chemical bonding, while oxygen vacancies induced by carbon dots act as exciton traps to prolong afterglow. By cascading FRET with commercial dyes, we achieve tunable emission from yellow to red. The simple, catalyst‑free, one‑step synthesis and the use of low‑cost, renewable rosin make this process readily scalable. Potential industrial applications include water‑resistant anti‑counterfeiting inks, flexible 3D optical art labels, and emergency signage for fire scenes - where both sunlight excitability and extreme‑environment durability are essential.