Heterojunction photocatalysts could provide a potential strategy to solve the serious energy and environmental crises. However, the required heterojunction photocatalyts with high charge-separation efficiency and strong redox ability, which have unique dimensionality-dependent integrative and synergic effects, are intriguing but still underdeveloped. Here, for the first time, we design and fabricate 2D/2D heterojunctions between carbon nitride nanosheets and oxygen-vacancies confined in bismuth titanate mesoporous nanosheets. Especially, selective pollutant transformation of rhodamine B and 4-chlorophenol solutions under visible-light irradiation has been conducted by the use of 2D/2D heterojunction photocatalysts. Based on the steady-state and transient photoluminescence spectra and electron spin resonance technology, the Z-scheme energy-transfer mechanism is identified and the photogenerated charge carriers in the 2D/2D heterojunctions display a prolonged lifetime and higher separation compared to those in carbon nitride and bismuth titanate alone. This work will shed light on the rational design of more complex 2D/2D heterojunctions with accompanying applications in solar energy conversion and environmental remediation fields.