Graphitic carbon nitride (g-C3N4) has attracted tremendous attention in photocatalysis due to its extraordinary features, such as good thermal and chemical stability, metal-free composition, and easy preparation. However, the photocatalytic performance of g-C3N4 is still restricted by the limited surface area, inefficient visible light absorption, and high recombination rate of photoinduced charge carriers. Herein, a facile synthesis to produce freestanding g-C3N4 photonic crystals (PCs) by crack-free, highly ordered colloid crystals templating is reported. The PC structure succeeded from the silica opals induces bicontinuous framework, stronger optical absorption, and increase in the lifetime of photoexcited charge carriers compared to that of the bulk g-C3N4, while the chemical structure remains similar to that of the bulk g-C3N4. As such, the g-C3N4 PCs have a much higher photodegradation kinetic of methyl orange and photocatalytic hydrogen production rate which is nearly nine times the rate of bulk g-C3N4.