The present invention relates to a
polymer carbon nitride, a specific
crystal form of the
polymer carbon nitride, and a cosmetic composition, an
ultraviolet ray-blocking composition, and an external use
skin preparation composition, which include the
polymer carbon nitride. The polymer carbon
nitride according to one aspect of the present invention and a
crystal form produced by a specific preparation example thereof can absorb both UVA and UVB, and thus can effectively protect the
skin from
ultraviolet rays while also being non-toxic and thus suitable for living bodies and lacking photoactivity. Therefore, the polymer carbon
nitride and the
crystal form can be utilized in a cosmetic composition, an
ultraviolet ray-blocking composition and an external use
skin preparation composition, which are applied to the
living body. Moreover, the specific crystal forms of the polymer carbon
nitride have different characteristics according to the manufacturing method, and thus may be used in a variety of ways according to the characteristics. Particularly, the crystal form of the polymer carbon nitride according to one aspect can be adjusted to various colors according to the preparation method, and thus can be utilized to obtain a composition having a desired color. Therefore, the crystal form can be suitably utilized to produce products of various colors suitable for the skin tones of individuals.