Circularly polarized light is central to photonic technology. A key challenge lies on developing a versatile and scalable strategy using sustainable materials that is capable of generating circularly polarized light with tailorable chiroptical activity. We show that left-handed chiral nematic cellulose nanocrystal-based films have intrinsic ability to transform spontaneous emission within the photonic bandgaps to high dissymmetry right-handed circularly polarized fluorescence. We present that the circular polarization ability of chiral nematic cellulose nanocrystal films can be extended to produce ambidextrous reflection and fluorescence through synergistic self-assembly and kinetic intercalation of nematic phases. We demonstrate that self-emissive chiral nematic mesoporous inorganic films, which are the reverse replica of chiral nematic cellulose nanocrystal, enable room-temperature right-handed circularly polarized phosphorescence with several-second afterglow in the visible regime. The potential of cellulose nanocrystal-based films for optical encryption and anti-counterfeiting optical labels is illustrated. Our work provides a step towards rational organization of sustainable and scalable chirophotonic materials with tailorable circular polarization properties that can be imporant to diverse technological applications.