Fe doped bimetallic HKUST-1 MOF with enhanced water stability for trapping Pb(II) with high adsorption capacity

Abstract

HKUST-1 Metal-Organic Framework (MOF), due to its coordinatively unsaturated metal sites, high surface area and microporosity, is one the most prominent MOF candidates. Our study investigates the consequence of doping iron into HKUST-1 MOF on its hydrostability, and demonstrates its usability for Pb(II) removal. A simple one-pot solvothermal process was used to synthesize Fe doped HKUST-1 MOF with varying dopant concentrations of Fe (5-20 mol%). Through various characterisation techniques (XPS, XRD, FTIR, ICP-OES) and MD simulations we demonstrated the incorporation of Fe into the HKUST-1 framework, which happened through Fe substituting the Cu(II) sites. Water stability studies using experimental and modelling approaches demonstrated that partial substituted Fe-HKUST-1 MOFs have a greater surface area retention with very little loss in crystallinity as compared to pristine HKUST-1 MOF. Fe substitution of as low as 5 mol% yielded a significant enhancement in the hydrostability of HKUST-1 MOFs, wherein the structure was intact for up to 10 hrs of water treatment. Similarly, 5 mol% Fe doping had a 53% reduction in the amount of Cu being leached out from the HKUST-1 MOF framework. Fe doped HKUST-1 MOFs showed exceptionally high Pb(II) selectivity, Pb(II) removal efficiency of >90%, and a high Pb(II) adsorption capacity of 565 mg g-1. This study opens up the possibility of using doping as a strategy to enhance the hydrostability of HKUST-1 MOF and in the process improve its applicability for environmental remediation applications.