Eco-friendly preparation of K+-doped HKUST-1 metal organic framework for adsorptive collection of CO2 or volatile organic vapors

Abstract

This study aims to develop a one-pot, eco-friendly synthesis of K-HKUST-1 via ultrasonication and compare its performance with various non-conventional methods. K-HKUST-1 synthesized by ultrasonication in 30 min exhibited the highest CO₂ adsorption capacity (6.19 mmol/g) and CO₂/N₂ selectivity (24.92), consistent with its highest surface area and pore volume compared to the K-HKUST-1 synthesized by conventional methods. K-HKUST-1 retained its CO₂ adsorption capacity (5.17 mmol/g) after exposure to a humid environment for 20 days, which is significantly higher than the parent HKUST-1 (1.27 mmol/g). The SEM-EDS analysis and density functional theory (DFT) calculations revealed that successful K⁺ doping into the HKUST-1 framework increases CO₂ adsorption capacity, attributed to additional adsorption sites created by K⁺ doping. Notably, this study is the first to demonstrate alkali metal doping directly into the MOF framework using an eco-friendly approach, instead of traditional solvothermal methods or post-synthetic modifications, representing a major advancement in the field. Furthermore, the optimum K-HKUST-1 sample was evaluated for acetone, benzene, toluene, and p-xylene adsorption, showing capacity increases of 21 % for acetone, 38 % for benzene, 45 % for toluene, and 27 % for p-xylene compared to the parent HKUST-1 making it a promising candidate for carbon capture and VOCs removal applications.