Amine-modified MOF-14 as a tunable platform for CO2 adsorption and supercapacitor energy storage

Abstract

Amine-functionalized copper(II)-based MOF-14 materials were prepared via post-synthetic modification using ethylenediamine (en), diethylenetriamine (deta), and 1,2-bis(3-aminopropylamino)ethane (bape) at varying incorporation levels. Comprehensive structural, morphological, textural, and thermal analyses verified the successful grafting of amine functionalities while maintaining the integrity of the parent framework. CO₂ adsorption studies at 0 °C demonstrated that en- and deta-modified MOF-14 exhibited optimal uptake at loadings of 10–15 wt%, achieving a balance between enhanced chemisorption sites and accessible pore volume, whereas the larger bape ligand led to substantial pore obstruction. Additional adsorption measurements at 25 °C confirmed measurable CO₂ uptake under conditions closer to practical gas separation processes. Furthermore, evaluation of CO₂/N₂ separation performance, including IAST calculations for a 15% CO₂/85% N₂ mixture, revealed substantially enhanced selectivity in the amine-modified frameworks compared to pristine MOF-14. Electrochemical evaluation revealed the excellent energy storage performance of MOF-14 (en) 20%, delivering a high specific capacitance of 972 F g⁻¹, markedly outperforming the pristine material. This study highlights the dual capability of amine-modified MOF-14, presenting efficient low-pressure CO₂ capture alongside outstanding promise as an electrode material for high-performance supercapacitors.