Introducing sulfonic acid polymers into MOF nanochannels for ultra-high Ba2+ adsorption capacity and proton conductivity

• Published in: Separation and purification technology 2024-09, Vol.343, p.127133, Article 127133
• Main Authors: Luo, Guoqin, Jiang, Jiashan, Wei, Shiyu, Huang, Chao, Chen, Dongmei, Zhu, Bixue, Zhang, Shunlin
• Format: Article
• Language: English
• Subjects: Ba2+ adsorption; Polymer-MOFs composites; Proton conduction; Sulfonic acid
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2024.127133

[Display omitted] •Modification of MOF nanochannels with high concentrations of sulfonic acid by introducing polymers into the nanochannels of the MIL-101 series.•The MOF composites exhibited outstanding barium ion adsorption capacity with maximum uptakes of 356.9 mg·g−1.•The MOF composites also exhibited superior proton conductivity with maximum values of 1.43 × 10−1 S·cm−1 at 85 °C and 98 % RH. Porous materials with a high concentration of sulfonic acid groups are highly desirable for applications such as radioactive Ba2+ adsorption, catalysis, and proton-conductive materials, but they are also challenging to synthesize. In this work, we introduce polymers containing sulfonic acid groups into the nanochannels of metal–organic frameworks (MOFs) through in-situ synthesis to enhance the sulfonic acid content. We use a alkene with sulfonic acid groups (2)-acrylamido-2-methylpropane sulfonic acid, AMPS) and a crosslinking agent N,N’-methylenebisacrylamide (MBAA) to synthesize two MOF composites, PAMPS@MIL-101 and PAMPS@MIL-101-SO3H, in the ultra-stable MIL-101 series through in-situ polymerization with free radical initiators. The two MOF composites have a high and uniform distribution of sulfonic acid groups in the MOF framework, which results in ultra-high barium ion adsorption capacity. The maximum adsorption amounts are 142.7 and 356.9 mg·g−1 for PAMPS@MIL-101 and PAMPS@MIL-101-SO3H, respectively, which are higher than those of most reported adsorbents. Importantly, the adsorption equilibrium can be achieved within 20 min. Moreover, both MOF composites, PAMPS@MIL-101 and PAMPS@MIL-101-SO3H, exhibit super proton conductivity, with values of 6.43 × 10−2 S·cm−1 and 1.43 × 10−1 S·cm−1 at 85 °C and 98 % RH, respectively. This method offers a new way of modifying MOF nanochannels with high sulfonic acid concentrations, and opens up new opportunities for developing radioactive Ba2+ adsorption materials and proton-conductive materials.