Enhancement of Hydrogen Adsorption on Spray-Synthesized HKUST-1 via Lithium Doping and Defect Creation

Abstract

We prepared HKUST-1 (Cu₃BTC₂; BTC^3- = 1,3,5-benzenetricarboxylate) using a spray synthesis method with Li doping and defect created via partial replacement of H₃BTC with isophthalic acid (IP) to enhance the H₂ adsorption capacity. Li-doping was performed by incorporating LiNO₃ in HKUST-1 via spray synthesis and subsequent thermal treatment for decomposing NO₃^-, which enhances H₂ uptake at 77 K and 1 bar per unit mass and per unit area from 2.37 wt% and 4.16 molecules/nm² for undoped HKUST-1 to 2.47 wt% and 4.33 molecules/nm², respectively. Defect creation via the replacement of the BTC^3- linker with the IP^2- linker slightly in HKUST-1 skeleton did not affect H₂ uptake. Both Li-doping and defect creation significantly enhanced H₂ uptake to 3.03 wt%, which was caused by the coordination of Li ions with free carboxylic groups of the created defects via IP replacement.

Keywords: HKUST-1; defect creation; hydrogen adsorption; lithium doping; metal–organic frameworks.