Achieving Efficient Lifetime-Tunable Room-temperature Phosphorescent Cellulose with Excitation Wavelength- and Time-Dependence.

The precise modulation of the lifetime and the responsive properties of room-temperature phosphorescence (RTP) is essential for realizing its multifunctional applications. Herein, a facile strategy is presented to achieve a series of cellulose benzoate esters (CBE-X, X = H/CH3/OH/NH2) with lifetime-tunable RTP through substituent engineering. Enhancing the electron-donating ability of CBE-X effectively modulates the HOMO-LUMO gap, exciton energy, spin-orbit coupling, and interaction between cellulose chains, thereby enabling control over the RTP lifetime. The RTP lifetime of CBE-X can be increased from the initial values of tens of milliseconds to over 1000 ms. Notably, the CBE-NH2 film with an electron-rich substituent achieves an ultra-long RTP lifetime of 1046 ms and a quantum yield of 53.42%. Furthermore, the aggregation of diverse clusters on cellulose chains endows these films with unique excitation wavelength- and time-dependent afterglow, providing novel concepts for multidimensional dynamic optical coding. This study establishes the clear structure-property relationship between substituent's electronic characteristics and RTP performance in cellulose-based systems, providing both theoretical insights and a sustainable design paradigm for eco-friendly phosphorescent materials.