Temperature-induced phase transitions of 2D ALHPs have been reported in many experiments, including studies on (BA) 2 (MA)Pb 2 I 7 perovskite. As the temperature decreases, these perovskites experience a transition from a high-symmetry orthorhombic system to a lower-symmetry triclinic one. This reversible phase transition is characteristic of firstorder order-disorder transitions, driven by the melting of the spacer alkylammonium chains.