Enhancement of H2 physisorption in covalent organic Framework's linkers by Li-decoration

• Published in: International journal of hydrogen energy Vol. 79; pp. 1139 - 1154
• Main Authors: Joshi, Himani, Pakhira, Srimanta
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 19.08.2024
• Subjects: Binding enthalpy; Covalent organic frameworks (COFs); Density functional theory (DFT); Linkers; Lithium; Physisorption; Lithium; Binding enthalpy; Linkers; Covalent organic frameworks (COFs); Physisorption; Density functional theory (DFT)
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2024.06.348

Our rigorous investigation, employing first principles-based dispersion-corrected density functional theory (DFT-D) and second-order Møller-Plesset perturbation theory (MP2) methods, has illuminated the remarkable promise of lithium-decorated organic linkers of Covalent Organic Frameworks (COFs). We have computationally designed 36 complexes with nine pure linkers of COFs and Li-decorated linkers, and these designed linkers show the physisorption of H2 molecules. The synergy of Li atoms with these linkers shows a Li binding energy about −0.5 to −1.3 eV, which enables each Li atom to capture two H2 molecules with an average ΔH per H2 molecule about -0.02 to -0.20 eV. We computationally obtained a significant weight percentage (wt.%) of H2 uptake, with a maximum of wt.% for the molecular structure of Linker-3 using DFT-D methods. The true highlight of our work is the average binding enthalpy of -0.20 eV per H2 molecule when coupled with Li-decorated Linker-5. Our study unveils the intricate interplay between dispersion and electrostatic forces that play a dominant role in binding enthalpy. We performed GCMC simulations in our designed pure COFs to study the H2 uptake at 77 K and 298 K at varying low and high-pressure ranges. COF-IITI appears more effective in absolute H2 loading than the Pristine COF because of its larger surface area. This groundbreaking research is essential for realizing efficient, secure, compact, and cost-effective hydrogen storage materials. It aligns perfectly with the ambitious goals set by the U.S. Department of Energy, propelling us closer to a sustainable energy future. [Display omitted] •A Li-decoration technique is proposed to enhance H2 uptake in COF's linkers.•The Li binding energy for COF's linkers lies in the range of -0.5 to -1.3 eV.•The H2 binding enthalpy in Li-decorated linkers satisfies the physisorption.•Dispersion and electrostatic interactions play a major role in binding enthalpy.