Sorption Thermal Energy Storage Performance of Nanoporous Metal-Organic Frameworks and Covalent Organic Frameworks by Grand Canonical Monte Carlo Simulations

Developingmaterials with outstanding performance for sorptionthermal 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 totheir excellent adsorption properties, including large capacitiesand stepwise adsorption isotherms. However, the energy density (Q (ed)), an essential property to look at when choosinga suitable material for STES, is still elusive due to the differentcomposition methods in the experiment. This work evaluated and comparedthe material-based Q (ed)'s of MOFsand COFs for STES via grand canonical Monte Carlo simulations. Itwas demonstrated that most MOFs exhibited larger Q (ed) than COFs since MOFs tend to have high loading duringthe charging process. Nevertheless, it was found that one COF exhibitedthe highest Q (ed) ascribed to the low densityand complete desorption during the discharging process, which suggestedthat COFs can possess excellent performance as long as they achievesufficient capacity during the charging process. Moreover, the structure-propertyrelationship indicated that large pore volume, relatively small density,suitable carbon atom ratio, and isotropic 3D cage were favorable forlarge-Q (ed) structures. The successful implementationof data mining and machine learning algorithms paves the way for rationaldesign and speeds up the assessment of the Q (ed) of nanoporous materials.