In conclusion, we have synthesised a new series of [A]Ni(C2N3)3 molecular perovskites, showing that framework distortions are sensitive towards small chemical changes of A + . Subsequently, we applied this series to establish a link between the size and globularity of A + , the active distortion modes in the [Ni(C2N3)3] - framework and the pressure responsiveness of the molecular perovskites for the first time. In the absence of HBIs and changes in chemical bond strength within the network, we conclude that Ap is the decisive parameter in defining the compressibility of a molecular perovskite. Additionally, we show tunability of Ap, and thus B, through the synthesis of A-site solid solutions. Such a tunability of B via chemical modifications advances our understanding of underlying compositionstructure-property relations and paves the way for the targeted design of molecular perovskites' mechanical properties for applications such as barocalorics. Additionally, the here applied methodology to link network distortions and the pressure responsiveness is of general nature, with implications for the analysis of the high-pressure responsiveness of closely related material families, including metal-organic frameworks, covalent organic frameworks and hydrogen-bonded frameworks.