The Role of Pore Diameter on Tuning the Hydrogen Storage Capacity of Yttrium Atom‐Decorated Covalent Organic Frameworks: A Theoretical Study

ABSTRACT The electronic structure and hydrogen storage properties of benzene‐based covalent organic frameworks (COFs) with pore diameters of 0.53, 0.99, and 1.45 nm are studied using density functional theory calculations. The studied COFs show poor H 2 molecule adsorption properties. To enhance their H 2 molecule adsorption properties, Y atoms are decorated on the COFs with an average binding energy of about 5–6 eV per Y atom. Each Y atom of Y‐decorated COFs, YCOF1, YCOF2, and YCOF3 effectively adsorbs six H 2 molecules with an average H 2 adsorption energy of −0.28, −0.34, and −0.35 eV per H 2 molecule, respectively. The H 2 molecule storage capacity of YCOF1, YCOF2, and YCOF3 is found to be 4.7%, 5.1%, and 6.5% with desorption temperatures of 358, 434, and 447 K, respectively. The findings show that a larger pore diameter provides more space for metal atom decoration and thereby increases the H 2 molecule adsorption capacity. The H 2 molecule adsorption weight percentage of YCOF3 meets the target H 2 molecule storage capacity suggested by the U.S. Department of Energy and Fuel Cells and Hydrogen Joint Undertaking (FCH‐JU) in Europe.