Photocatalyst derived from 0D/2D heterojunction composite is highly attractive for their great potential in environmental remediation and energy conversion. Herein we constructed a 0D/2D heterojunction built from carbon quantum dots (CD) and carbon nitride sheets (GCN) by microwave irradiation, which ensures the uniform dispersion of CDs. The electric field generated at the interface of this heterojunction favored the prevention of rapid recombination of photogenerated charge carriers. The successful heterojunction formation is due to the uniform dispersion of CDs, acting as electron sink over the sheets. A four‐fold enhancement in photocatalytic activity is obtained for this heterojunction, compared to pristine carbon nitride. With the support of the scavenger studies, the possible mechanism behind the photocatalytic activity is proposed. Interestingly, herewith we report an eco‐friendly method for the synthesis of CD/GCN composite material by using cheaply available and non‐hazardous precursors such as urea and glucose.