Producing thermoplastic room temperature phosphorescent (RTP) materials with closed-loop recyclability from natural sources is an attractive approach but hard to achieve. Here, the study develops such RTP materials, Poly(TA)/Cell, by thermally polymerizing thioctic acid in the presence of cellulose. Specifically, polymerized thioctic acid poly(TA) forms strong hydrogen bonding interactions with CNF, promoting formation of molecular clusters between the oxygen-containing units. The as-formed clusters generate humidity- and excitation-sensitive green RTP emission. Red afterglow emission is also obtained by integrating Poly(TA)/Cell together with Rhodamine B (RhB) via an energy transfer process. Attributed to the thermoplastic properties, the as-obtained Poly(TA)/Cell can be thermally molded into flexible shapes with uncompromised RTP performance. Moreover, owing to the alkali-cleavable properties of the disulfide bond in Poly(TA)/Cell, thioctic acid and cellulose can be successfully recycled from Poly(TA)/Cell with a yield of 92.3% and 81.5%, respectively. As a demonstrator for potential utility, Poly(TA)/Cell is used to fabricate materials for information encryption.