Fabrication of adsorbents with enhanced CuI stability: Creating a superhydrophobic microenvironment through grafting octadecylamine

Abstract

In atmospheric conditions, CuI is easily oxidized to CuII due to the coexistence of moisture and oxygen. The poor oxidation inhibition of CuI restricts the practical application of CuI-containing materials. Herein we introduce an approach to construct a superhydrophobic microenvironment in CuI-functionalized metal–organic frameworks by coordinatedly grafting organic amine compounds onto open metal sites (OMSs), which can hinder the accessibility of moisture to pores thereby enhancing the stability of CuI. As a proof of concept, MIL-101(Cr) with abundant OMSs and octadecylamine (OA) with long hydrophobic alkyl groups are used as carrier and surface coating. As superhydrophobic porous materials, the resultant CuIM-OA exhibits improved CuI stability in addition to retaining high crystallinity and intact porosity while almost all CuI is oxidized in hydrophilic CuIM upon exposure in a humid atmosphere for 30 h. CuIM-OA owns excellent adsorption desulfurization performance (ADS) with regard to thiophene, benzothiophene, and 4,6-dimethyl dibenzothiophene. Even from hydrated fuel, the adsorption performance of CuIM-OA maintains well while the adsorption capacity of CuIM decreases to 7% after 4 cycles. The remarkable moisture resistance, CuI stability, and high porosity make the current adsorbent CuIM-OA highly promising for the practical ADS process.