Highly photoluminescent carbogenic nanoparticles (CNPs) have been prepared in MAPO-44, a Mg-substituted aluminophosphate molecular sieve with a chabazite structure, through thermal decomposition of the occluded template or loaded organic molecules. The resulting composite phosphors can be excited by a broad range of light in the ultraviolet region, and the emission wavelength is tunable through varying the thermal treatment condition. It is demonstrated that the emission wavelength is dependent on the carbon content in the composite phosphor materials, and the higher the content, the longer the emission wavelength. Correspondingly, upon excitation at a single UV wavelength, the emission color is finely tuned from violet to orange-red for samples with various carbon contents. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spectroscopy have been employed to elucidate the nature of the carbonaceous species in the phosphors. Heterogeneity or defects have been found to be prevalent in the CNPs of the composite phosphor materials, and it is these defects that form surface states responsible for the photoluminescence of the materials.