Tailoring Pore Size in Anionic MOFs Toward Enhanced Selective Adsorption of Organic Dye Pollutants

Organic dye pollutants pose a serious threat to ecosystems and human health, whereas there still exist challenges in efficient and selective adsorption of them due to the difficulty in structure tunability of traditional adsorption materials. Based on the tailorable pore structure of anionic metal-organic frameworks (MOFs), the pore size can be optimized to match the dye molecules through a solvothermal control strategy, thereby achieving efficient adsorption. Herein, the pore size of anionic MOFs was modulated by varying solvents and temperature, facilitating high-performance selective adsorption of cationic dye via a large-pore size effect. The optimized MOF (Bio-MOF-100) of large pore size achieved a methylene blue adsorption capacity is high to 443.01 mg/g, which is approximately 2.45 times higher than that of the MOF (Bio-MOF-1) before pore regulation. Using a mixed matrix membrane (MMM) strategy, the optimized MOF was mixed with polyvinylidene fluoride (PVDF) to form a membrane. The membrane is not only portable and recyclable, but also inherits the characteristics of MOFs, enabling selective adsorption of cationic dyes. Its maximum adsorption capacity for methylene blue is 141.78 mg/g. These results provide an example for the design and utility of largely-pore MOFs for targeted pollutants adsorption.