How to achieve multicolor organic room-temperature phosphorescence (RTP) is still challenging and striking. Herein. we discovered a new principle to construct eco-friendly color-tunable RTP nanomaterials based on the nano-surface confining effect. Cellulose nanocrystal (CNC) immobilized cellulose derivatives (CX) containing aromatic substituents via hydrogen-bonding interactions. https://www.nacrack.com/