Disulfide-Functionalized Porous Organic Cage for Efficient Adsorptive Removal of Hg(II) from Aqueous Solutions

The removal of water pollutants through adsorption by porous materials has been demonstrated to be an effective method due to its relatively low cost, simple design, ease of operation, and regeneration capabilities. In this study, we assembled three robust porous organic cages (POCs), namely CPOC-109, CPOC-110, and CPOC-111, from the same tetraformyl-functionalized calix[4]resorcinarene (C4RACHO) cap and three different types of diamino linkers, with the number of sulfur atoms ranging from 0 to 2. Single X-ray crystallographic analysis reveals that all three CPOCs exhibit [2 + 4] lantern-shaped structures with large intrinsic cavities, having heights and cavity volumes ranging from 1.74 to 1.80 nm and 1023.42 to 1157.66 Å3, respectively. Furthermore, 77 K N2 gas adsorption measurements suggest that all CPOCs exhibit high porosity, with Brunauer–Emmett–Teller (BET) specific surface areas reaching up to 700 m2 g–1. Leveraging their porous nature and rich coordination sites (N, O, and S), the application of these CPOCs for the adsorptive removal of Hg(II) from aqueous solutions was explored. Notably, CPOC-111 demonstrated superior Hg(II) adsorption capacity (220.26 mg/g) compared to CPOC-109 and CPOC-110. Additionally, CPOC-111 exhibited excellent cycling performance and maintained good adsorption stability within a broad pH range of 3 to 11. This study serves as a compelling example of using POC adsorbents for the removal of Hg(II) ions from water and highlights the potential for expanding the application of POC materials in environmental remediation and pollution control.