Pyrazole-functionalized chitosan aerogel for selective capture of iodine vapor and methyl iodide under complex conditions

This study achieved the directed functionalization of 3-aminopyrazole onto the interface of chitosan aerogel via the Schiff base reaction, successfully preparing a porous, lightweight, lamellar pyrazole-functionalized chitosan aerogel material (Pyrazole@CSA-5). This material demonstrates specific and efficient capture of iodine vapor and methyl iodide under strong acidic, high-humidity, and low-concentration dynamic conditions. At 75 °C, Pyrazole@CSA-5 achieved capture capacities of 5255 mg/g for iodine vapor and 1060 mg/g for methyl iodide. Under dynamic low-concentration conditions, the material maximum capture capacities for iodine vapor (8.75 ppm) and methyl iodide (18.6 ppm) were 1658 mg/g and 410 mg/g, respectively, significantly outperforming similar adsorbents. Mechanism characterization revealed that Pyrazole@CSA-5's adsorption of iodine vapor and methyl iodide is attributed to electron transfer with imine groups and nitrogen methylation reactions with imine groups, respectively. DFT calculations revealed adsorption energies of −0.70 eV and −0.57 eV for iodine, −0.70 eV and −0.61 eV for methyl iodide at the two distinct imine sites, confirming the material's outstanding adsorption performance toward both iodine vapor and methyl iodide. After treatment with the strong acid at pH = 1, Pyrazole@CSA-5 exhibited the iodine vapor capture capacity of 4125 mg/g. Under 80 % humidity conditions, its capture capacities for iodine vapor and methyl iodide were 3735 mg/g and 1007 mg/g, respectively, maintaining good capture performance. Thus, Pyrazole@CSA-5 demonstrates effective specific capture of iodine vapor and methyl iodide under complex conditions, exhibiting strong potential for practical application.