  Optimizing energy and charge transport is key in design and implementation of
efficient two-dimensional (2D) conductive metal-organic frameworks (MOFs) for
practical applications. In this work, for the first time, we investigate the
role of both long-range excitonic and short-range charge transfer (CT) coupling
as well as their dependency on reorganization energy on through-space transport
properties in 2D MOFs. A pi-stacked model system is built based on the
archetypal Ni3(HITP)2 2D MOF and a Frenkel/CT Holstein Hamiltonian is developed
that takes into account both electronic coupling and intramolecular vibrations.
The dependency of the long and short-range couplings of both secondary building
units (SBUs) and organic linkers to different dynamical motions in 2D MOFs are
evaluated which predicts that photophysical properties of 2D MOFs critically
depend on the degree of ordering between layers. Using the model system, we
show that the impact of the two coupling sources in these materials can be
discerned or enhanced by sliding of the SBU in a cofacial configuration along
the long- or short molecular axis. The effects of vibronic spectral signatures
are examined for integrated Frenkel/CT systems in both perturbative and
resonance regimes. Although to the best of our knowledge sliding engineering in
2D MOFs currently remains beyond reach, the findings reported here offer new
details on the photophysical structure-property relationships on 2D MOFs and
provide suggestions into how to combine elements of molecular design and
engineering to achieve desirable properties and functions for nano- and
mesoscale optoelectronic applications.
