Two novel potassium pentazolate frameworks KN5·1.5CH3COOK (1) and KN5·3CF3COOK (2) were achieved by changing the content and type of K-carboxylates. All the compounds were characterized via infrared (IR), single-crystal X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. 1 exhibited two unique nanocages featuring KN5 and CH3COOK. 2 with a high density (2.097 g cm−3) was constructed by replacing the H atoms of 1 with the most electronegative F atoms. The F atoms of 2 form channels that constituted a peculiar porous structure. The electronegativity, atomic charge, and electrostatic potential were further analyzed for the differences between the two frameworks and explained the reasons for the constitution. This work demonstrates that it is possible to regulate the crystal structure and density through appropriate additives.