Enhancement effect of lithium-doping functionalization on methanol adsorption in copper-based metal-organic framework

Abstract

Grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) calculations were performed to evaluate the functionality effect of Li-doping on methanol adsorption over copper-based metal–organic frameworks (MOFs). In this work, a new Li-doping structure, Cu-BTC-Li, was theoretically constructed by introducing Li above both sides of organic linkers in Cu-BTC. Compared to the original Cu-BTC, Cu-BTC-Li shows higher methanol capacity and more continuous adsorption behavior in the measured pressure range. It can be attributed to the new adsorption sites (Li-sites) created by Li atoms, which turn to be the first preferential adsorption sites instead of Cu-sites, as revealed by the more exothermic binding energies (BEs) on Li-site (−90.55kJ/mol) than the latter (−45.14kJ/mol). Li-doping also shows varied effects on methanol adsorption at different pressures. The electrostatic interaction between methanol and framework plays a predominant role (with contribution over 95%) in the adsorption at low pressures, and Li-doping enhances adsorption by increasing the electrostatic potential of the framework. Although the dispersive interactions govern the adsorption at high pressures, Li-doping contributes to the dispersion. The present Li-doped functionalization can be extended to design new MOFs with high performance of alcohol capture in the future.