Adsorption and photocatalytic degradation of aqueous methylene blue using nanoporous carbon nitride

[Display omitted] •Synthesis of CaCO3 nanoparticle by the reverse micelle method.•Utilizing CaCO3 nanoparticles as templating agent for synthesis of nanoporous g-C3N4.•High adsorption and visible light harvesting of nanoporous g-C3N4 versus bulk g-C3N4.•Utilizing adsorption and photodegradation characters of nanoporous g-C3N4 in water treatment. Nanoporous graphitic carbon nitride (npg-C3N4) with high performance was synthesized as visible light harvesting photocatalyst. Calcium carbonate (CaCO3) nanoparticles were synthesized and used as a templating agent along with melamine, as the precursor, for the synthesis of npg-C3N4. High porous npg-C3N4, having a specific surface area of 137.4 m2 g−1, was resulted with enhanced ability in visible light harvesting. At the mass ratio of melamine/CaCO3 = 5/4, its photocatalytic performance was 42 times higher than that of the bulk g-C3N4 when methylene blue (MB) was used as adsorbate and probe. Adsorption and kinetic isotherm showed that the adsorption process can be well described by pseudo-second-order kinetic model, with an adsorption capacity of 400.0 mg MB per gram adsorbent determined by Langmuir isotherm.