The realization of 2D/2D Van der Waals (VDW) heterojunction is an advanced approach to obtain superior photocatalytic efficiency. However, electron transfer through Van der Waals heterojunction formed through ex-situ assembly faces significant challenges at the interface due to their contrast morphologies and potential barriers of the substituents of the nanocomposites. Here, a novel approach involving the insertion of a phosphate group between copper phthalocyanine (CuPc) and B-doped and N-deficient g-C3N4 (BDCNN) to design and construct a Van der Waals heterojunction denoted as xCu[acs]/nPO4-BDCNN is presented. The introduction of phosphate as charge modulator and an efficient conduit for charge transfer within the heterojunction resulted in the spatial barrier elimination and induction of electrons from BDCNN to CuPc in the excited states. Consequently, the photoelectrons were captured by the catalytic central Cu2+ in CuPc leading to the conversion of CO2 to CO and CH4. Remarkably, this approach led to a 29-fold enhancement in the photocatalytic efficiency compared to pure BDCNN. By introducing "interfacial interacting" substances to establish an electron transfer pathway presents a novel and effective strategy for designing photocatalysts capable of efficiently reducing CO2 into valuable products.