Underwater oleophobic-super hydrophilic strontium-MOF for efficient oil/water separation

The oil spill clean-up from water bodies is a major challenge in recent years because of the rise in pollution due to human activities. To tackle these environmental issues, we report the use of the Strontium Metal-Organic Framework (Sr-MOF) for the application of oil–water separation. Herein, the separation is carried out through underwater oleophobic-super hydrophilic properties of the MOF. The Sr-MOF was successfully synthesized using a strontium metal source ([Sr(NO3)2]) and 1,4-benzenedicarboxylic acid (H2BDC) as the organic linker. The MOF showed an excellent separation efficacy of different oils with above 99 % oil rejection driven by gravity. Also, the underwater oil contact angle (UWOCA) of various oils was greater than 132° for Sr-MOF which obeys Cassie-Baxter's theory, due to which the MOF showed excellent oil separation. Interestingly, the flux was dependent on the kind of material the MOF is placed over i.e., for cotton bedding, the flux is above 500 Lm−2h−1 and for steel mesh bedding the flux is above 5000 Lm−2h−1. We have also demonstrated their reusability tests with the least number of 20 cycles which shows a constant rejection of oils. Due to the super-wetting properties, the MOF is stable through several cycles indicating that the Sr-MOF possesses an excellent potential for separating an oil–water mixture. This unique feature of Sr-MOF provides an interesting platform for the applications of MOFs for oil–water separation applications.