Light metals decorated covalent triazine-based frameworks as a high capacity hydrogen storage medium

Abstract

The structural stability and hydrogen adsorption capacity of an alkali (Li, Na and K) and alkali earth (Mg and Ca) metal atom decorated covalent triazine-based framework (CTF-1) are studied using ab initio density functional calculations. The calculation results revealed that Li, Na, K and Ca atoms can be adsorbed on the CTF-1 with the formation of a uniform and stable coverage due to the charge transfer between the metal atoms and the CTF-1 substrate, thus avoiding the clustering problem that occurs for the decoration of metal atoms on other substrates. The metal decorated CTF-1 could adsorb up to 30 hydrogen molecules with an average binding energy of ∼0.16–0.26 eV/H₂, corresponding to a gravimetric density of 12.3, 10.3 and 8.8 wt% for the CTF–Li₆, CTF–Na₆ and CTF–Ca₆ complexes, respectively, thereby enabling the Li, Na and Ca decorated covalent triazine-based frameworks to be very promising materials for effective reversible hydrogen storage at near ambient conditions.