Pickering Emulsions based on Sustainable MIL-101(Fe)/CNC Hybrid Nanoparticles for Effective Photocatalytic Degradation of Aqueous Dyes

Abstract Photocatalytic degradation of organic pollutants is an efficient, energy-saving, renewable technology. MIL-101(Fe) is an effective photocatalyst; however, its degradation efficiency for dye molecules is reduced by its hydrophobicity and sedimentation in aqueous solutions. In this study, MIL-101(Fe)/cellulose-nanocrystal (CNC) hybrid nanoparticles (MCs) with high photocatalytic activity were prepared by in situ growth. Owing to their unique amphiphilicity and interfacial adsorption, the MC-stabilised Pickering emulsions exhibited uniform particle size and stability. The MCs were uniformly adsorbed at the oil–water interface of the emulsion and dispersed in the water phase through a three-dimensional (3D) network with clusters. This facilitated complete contact of the MCs with pollutants, thereby significantly increasing the photocatalytic efficiency. The tuneable wettability of MIL-101(Fe) induced by CNCs considerably affected the stabilisation and photocatalytic degradation performance. At 0.5 wt% CNC, the MCs had a three-phase contact angle of 92°, resulting in the highest photocatalytic degradation rate and emulsion stability of the samples studied herein. An emulsion with a constant emulsification index of 100% was obtained at 0.4 wt% MCs and an oil-phase volume fraction of ~ 0.2. The MC-stabilised emulsion system exhibited high photocatalytic degradation efficiency for Rhodamine B. Moreover, the MCs could be recycled several times while ensuring a degradation efficiency within an acceptable range. Herein we introduce a new approach for improving and fabricating green, sustainable photocatalysts for degradation of organic pollutants in aqueous systems.