Water-resistant HKUST-1 functionalized with polydimethylsiloxane for efficient rubidium ion capture

Abstract

The water sensitivity of metal–organic frameworks (MOFs) significantly restricts their practical applications in rubidium ion (Rb(I)) capture from water. For solving this troublesome problem, we reported a series of synthesized water-resistant adsorbents—PDMS@HKUST-1 (PDMS represents polydimethylsiloxane) by using a facile PDMS-coating treatment on the bimetallic HKUST-1 surface. These composite materials (PDMS@HKUST-1) possess good wettability and exhibit excellent performance of Rb(I) adsorption from aqueous solutions. The performance of the adsorption process could be perfectly described by the Freundlich adsorption model and the pseudo-second-order equation. In addition, they are well-sustainable, maintaining nearly 100% of the initial Rb(I) uptake capacity after at least five recycles. Through material characterization including nitrogen adsorption–desorption, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), water contact angle measurements, and X-ray photoelectron spectroscopy (XPS), we proved that these coated adsorbents well inherited the original crystalline nature and pore characteristics of HKUST-1. In general, the PDMS@HKUST-1 material retains good porous structures after coating and this modified MOF displays an outstanding stability which is favorable for Rb(I) capture from aqueous solution.