High-efficient Ag(I) ion binding, Ag(0) nanoparticle loading, and iodine trapping in ultrastable benzimidazole-linked polymers

Interest in functional silver has rapidly grown over the years due to significant advances in separation, sensing, catalysis, and biomedical applications. Here we developed a new strategy to load single atomic silver species in the rigid and open unit of the fully conjugated benzimidazole-linked polymers (BILPs). Due to the well-defined chelating units of N-heterocycles, the Ag+ ion species can be coordinated by N ligands and stabilized in the atomic level without aggregating into nanoscale Ag clusters and nanoparticles. The obtained Ag+-BILP-101 exhibits a selective binding property of Ag+ ions from solutions. The ultrastable structure and the property of taking up metal species, endow BILPs with the advantages of functionalizing metal species. After the reduction by NaBH4, the Ag+ ions were transferred into Ag nanoparticles. The substantial and intrinsic porosity of BILPs also gives excellent accessibility to Ag species loaded in the frameworks. The plentiful N-heterocycles and loaded Ag species show a synergistic/coadsorption effect for iodine vapor, and the charge transfer from frameworks promotes the formation of iodide ions. The iodine capture capacities of Ag+-BILP-101 and Ag0-BILP-101 reach 3.3 g/g and 3.7 g/g at 80 ℃, and still maintain 3.2 g/g and 3.5 g/g at 150 ℃, respectively. After ethanol elution, the residual iodine/Ag molar ratios in Ag+/Ag0-BILP-101 samples are still more than one (about 1.5), suggesting their strong affinity toward iodine. This work highlights the excellent selective Ag+ ion binding and Ag species supporting properties of BILPs, which can extend to other porous organic framework platforms for various applications based on silver species-skeleton interactions.