Deciphering the emission mechanism of nonconventional luminogens and achieving persistent room temperature phosphorescence (p-RTP) from pure organic compounds have drawn increasing attention due to their significant fundamental importance and promising applications. Previous reports on nonconventional luminogens, however, mainly focus on fluorescence, while advances in pure organic p-RTP are generally restricted to aromatic crystals or host–guest systems. Herein, we report the unique intrinsic emission and moreover p-RTP in amorphous nonaromatic polymers of poly(acrylic acid) (PAA), polyacrylamide (PAM) and poly(N-isopropylacrylamide) (PNIPAM). These polymers are nonluminescent in dilute solutions, while being highly emissive in concentrated solutions, nanosuspensions and solid powders/films. This can be rationalized by the clustering-triggered emission (CTE) mechanism, as supported by further thermoresponsive emission, cryogenic and aggregation-induced emission (AIE) experiments, alongside single crystal analysis. Furthermore, PAA and PAM solids under ambient conditions, and PNIPAM solids under vacuum or under nitrogen, demonstrate distinct p-RTP, which can be enhanced through further ionization or pressurization. These results not only refresh our understanding of the emission mechanism of nonaromatic polymers, but also enable the facile fabrication and application of pure organic p-RTP luminogens from readily available compounds, thus providing an important step forward in both nonconventional luminogens and p-RTP.

A clustering-triggered emission (CTE) strategy, namely the formation of heterogeneous clustered chromophores and conformation rigidification, for achieving tunable multicolor phosphorescence in single-component compounds is proposed. Non-conventional luminophores comprising just oxygen functionalities and free of π-bonding, i.e., D-(+)-xylose (D-Xyl), pentaerythritol (PER), D-fructose (D-Fru) and D-galactose (D-Gal), were adopted as a simple model system with an explicit structure and molecular packing to address the hypothesis. Their concentrated solutions and crystals at 77 K or under ambient conditions demonstrate remarkable multicolor phosphorescence afterglows in response to varying excitation wavelengths, because of the formation of diverse oxygen clusters with sufficiently rigid conformations. The intra- and inter-molecular O⋯O interactions were definitely illustrated by both single crystal structure analysis and theoretical calculations. These findings shed new light on the origin and simple achievement of tunable multicolor phosphorescence in single-component pure organics, and in turn, have strong implications for the emission mechanism of non-conventional luminophores.