Pickering high internal phase emulsions stabilized by metal-organic framework nanoribbons

Abstract

Pickering high internal phase emulsions (HIPEs) stabilized by colloidal particles are of great practical significance in the formulation of food, pharmaceutical, cosmetic, paint products and the chemical oil flooding. Herein, we report that a manganese-based metal–organic framework (MOF) (Mn3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate)) nanoribbons synthesized by a simple solution method can stabilize water-in-oil (W/O) high-viscosity Pickering HIPEs with crude oil as oil phase for more than one month at 43 °C. The Mn3(BTC)2 nanoribbons assemble at the oil/water interface of HIPE, owing to its advantageous structural features with the size of several micrometers, thickness of about 100 nm and amphiphilicity originated from the hydrophilic metal ions and hydrophobic organic ligands. The phase behavior and properties of the as-prepared HIPEs strongly depend on the MOF concentration (CMOF) and internal phase volume fraction of water (Fw) of emulsion. The MOF dispersions and crude oil are miscible into stable W/O HIPEs at Fw = 75 % when the CMOF ranges from 50 ppm to 5000 ppm. More interestingly, the viscosity of W/O emulsions greatly increases as the Fw varying from 50 % to 80 % and a viscosity of 4.5 Pa·s is obtained at CMOF = 2000 ppm and Fw = 80 %, which is nearly 400 times higher than that of crude oil. Moreover, the pressure generated by HIPEs flowing in core is about 40 times more than that of water injection and can remain the highest stable value substantially. These results show that the MOF dispersions are favorable to form stable W/O emulsions with high internal phase volume fraction, which has a great potential in improving oil displacement efficiency of chemical flooding.