Developing
materials with outstanding performance for sorption
thermal energy storage (STES) is vital in utilizing renewable energy.
Metal–organic frameworks (MOFs) and covalent organic frameworks
(COFs) have attracted much interest for application in STES due to
their excellent adsorption properties, including large capacities
and stepwise adsorption isotherms. However, the energy density (Q
ed), an essential property to look at when choosing
a suitable material for STES, is still elusive due to the different
composition methods in the experiment. This work evaluated and compared
the material-based Q
ed’s of MOFs
and COFs for STES via grand canonical Monte Carlo simulations. It
was demonstrated that most MOFs exhibited larger Q
ed than COFs since MOFs tend to have high loading during
the charging process. Nevertheless, it was found that one COF exhibited
the highest Q
ed ascribed to the low density
and complete desorption during the discharging process, which suggested
that COFs can possess excellent performance as long as they achieve
sufficient capacity during the charging process. Moreover, the structure–property
relationship indicated that large pore volume, relatively small density,
suitable carbon atom ratio, and isotropic 3D cage were favorable for
large-Q
ed structures. The successful implementation
of data mining and machine learning algorithms paves the way for rational
design and speeds up the assessment of the Q
ed of nanoporous materials.