The present invention relates to nitrogen doped A2Nb4O11, which is represented by A2Nb4O11-xNx, to a process for the preparation thereof, and to a method for degradation of organic pollutants. The nitrogen doped A2Nb4O11 is a new photocatalyst for the photocatalytic degradation of organic pollutants in the waste water. The A2Nb4O11-xNx catalyst may be prepared by substituting some of the O elements of pure A2Nb4O11 with N elements, and a process for the preparation thereof comprises a step of doping of nitrogen with a nitrogen source through a solid state reaction. The new nitrogen doped A2Nb4O11 catalyst having a general formula A2Nb4O11-xNx has a narrower optical bandgap compared to pure A2Nb4O11, and therefore can be activated under the visible light range and it shows high efficiency in the degradation of organic pollutants.