  Two-dimensional (2D) halide perovskites (HPs) are promising materials for
various optoelectronic applications, yet a comprehensive understanding of their
dynamics is still elusive. Here, we offer insight into the dynamics of
prototypical 2D HPs based on MAPbI$_3$ as a function of linker molecule and the
number of perovskite layers using atomic scale simulations. We show that the
layers closest to the linker undergo transitions that are distinct from those
of the interior layers. These transitions can take place anywhere between a few
tens of Kelvin below to more than 100 K above the cubic-tetragonal transition
of bulk MAPbI$_3$. In combination with the thickness of the perovskite layer
this enables one to template phase transitions and tune the dynamics over a
wide temperature range. Our results thereby reveal the details of an important
and generalizable design mechanism for tuning the properties of these
materials.
