Lead halide perovskite CsPbBr3 quantum dots (QDs) possess several desirable features which enable them to be promising candidates for photocatalysis. However, the instability caused by their inherent liquid-like ionic properties hampers their further development. Herein, this work employs the surficial molecular modification strategy and a multi-dimensional structure design to ease the instability issue. The additive 2-phenylethanamine bromide (PEABr) can serve as a ligand to compensate for stripping the amine ligands and passivate the surficial bromide vacancy defects of CsPbBr3 QDs in photocatalysis. In addition, PEABr acts as a reactant to form 2D and quasi-2D perovskite nanosheets. The addition of a small amount of these nanosheets into QDs can enhance their general stability due to their unique layered structures. Moreover, PEABr can trigger the phase transition of cubic CsPbBr3 into tetragonal CsPb2Br5. The newly formed Z-scheme homologous heterojunctions further improve the catalytic performance. Simulated photocatalytic dynamics reveals that our multi-dimensional structure favors decreasing the reaction barrier energy and then facilitating the photocatalytic reaction. Therefore, the electron consumption rate of our multi-dimensional perovskites doubles that of pristine CsPbBr3 QDs and also has superior long-term stability.