Computational screening of covalent organic frameworks for hydrogen storage

Abstract

Covalent Organic Frameworks (COFs) have been considered as promising materials for gas storage applications due to their highly porous structures and tunable characteristics. In this work, high-throughput molecular simulations were performed to screen the recent Computation-Ready Experimental COF Database (CoRE-COF) for H2 storage a first time in the literature. Predictions for H2 uptakes were first compared with the experimental data of several COFs. Motivated from the good agreement between simulations and experiments, we performed Grand Canonical Monte Carlo (GCMC) simulations to compute volumetric H2 uptakes of 296 COFs at various temperatures and pressures and identified the best candidates which exhibit a superior performance for H2 storage. COFs outperformed several well-known MOFs such as HKUST-1, NU-125, NU-1000 series, NOTT-112 and UiO-67 at 100bar/77K adsorption and 5bar/160K desorption conditions. We also examined the effect of Feynman-Hibbs correction on simulated H2 isotherms and H2 working capacities of COFs to consider quantum effects at low temperatures. Results showed that the Feynman-Hibbs corrections do not affect the ranking of materials based on H2 working capacities, but slightly affect the predictions of H2 adsorption isotherms. We finally examined the structure-performance relations and showed that density and porosity are highly correlated with the volumetric H2 working capacities of COFs. Results of this study will be highly useful in guiding future research and focusing experimental efforts on the best COF adsorbents identified in this study.