Red and Time‐Dependent Phosphorescence Color Generated from Cellulose Carbonized Polymer Dots via Precise Core–Shell Structure Modulation

Achieving red room temperature phosphorescence (RTP) in sustainable materials is attractive but challenging due to the lack of sufficient through‐bond conjugation. Herein, a core–shell structure modulation strategy is proposed to activate red RTP and time‐dependent phosphorescence color (TDPC) in cellulose carbonized polymer dots (CPDs). The CPDs show dual RTP emission species of polymer shell with functional groups and carbon core with conjugation domain, which are responsible for the green RTP at 535 nm and red RTP at 610 nm, respectively. The ratio of the two emission species can be well regulated by modulating the core–shell structure. Whether the core or shell structure dominates RTP, the CPDs display monotonous green or red afterglow. Significantly, the dual RTP emission species can be simultaneously activated by precisely balancing the core–shell structure, leading to dynamic TDPC varying from red to green over time. This work uncovers the origin of core–shell dual emission centers of cellulose CPDs, providing an efficient and simple method toward TDPC and affording a promising sustainable material for information encryption and anti‐counterfeiting.