New carbazole-based conjugated frameworks for carbon dioxide capture and water purification: Insights on the adsorptive sites' chemistry

Environmental remediation has attracted global concerns in the last few years. Carbon dioxide and its climate change impact and water contamination, and scarcity directly influence human life. Looking for practical solutions to these environmental crises, we designed and synthesized three new solid sorbent materials based on the 9H-carbazole-3,6-diamine. The resulting three materials, termed CCF-1, CCF-2, and CCF-3 were synthesized and characterized using solid-state NMR and FT-IR. CCF-1 showed the highest CO₂ uptake of 34 cm³ g⁻¹ (1.5 mmol/g) at 273K and 1 bar. The three polymers showed excellent performance in removing toxic metal ions (lead; Pb²⁺), (chromium; Cr³⁺), (arsenic; As³⁺), (nickel; Ni²⁺), (copper; Cu²⁺), and (mercury; Hg²⁺) from the water up to 98% Pb removal. Additionally, the materials were also investigated for the adsorption of methylene blue, methyl red, phenol, and bisphenol as common organic contaminants from wastewater. Finally, tuning the polar functionality of the constructed frameworks has led to good results and structure correlation in carbon dioxide capture and wastewater purification. The study of the adsorption site interaction in the dual application of carbon dioxide and metal ion removal in the three functionalized carbazole frameworks highlights the main criteria for designing porous materials for environmental remediation.