However, the OTO angles, also known as tetrahedral angles, represent the angles between the 4MR and helical chain, giving rise to six symmetrically independent OTO angles. Among these, we focused on two vertical angles to each other within the TO4 tetrahedron. One of these angles increased by approximately 3.6º, while the other decreased by about 3.2º; the remaining four OTO angles remained rigid (Table , Figure ). The position of the increased OTO angle (α, hereafter) precisely aligned with the position of the rotating angle θ, and their changes exhibited a similar trend (Figure ). This indicates that the molecular origin of this mechanical behavior lies in the selective deformation of the OTO angle α. In contrast, in case of gis-zeolites, OTO angles are more rigid than TOT angles under mechanical stimuli, resulting in different mechanisms with a constant rotating angle θ (Figure ). ). Calculated thermal expansion coefficients confirmed that the thermal expansion of gis-ZIF-2 is notably restrained by the presence of bulky components, with maximum values are 55.3⨯10 -6 K -1 for a parameter and 91.9 ⨯10 -6 K -1 for the cell volume, observed at 200K (Table , Figure ). Similar to gis-ZIF-1, gis-ZIF-2 also maintains rigid components with less than 0.1 Å change across the temperature range (Table , Figure ).