A New Covalent Organic Framework Modified with Sulfonic Acid for CO2 Uptake and Selective Dye Adsorption

Environmental pollution is one of the most severe problems facing the earth today, including water pollution and the greenhouse effect caused by the indiscriminate discharge of organic dyes and abundant carbon dioxide emissions (CO2), respectively. Therefore, removing dyes from water and eliminating CO2 in the atmosphere is an urgent issue that needs to be solved. Among them, with low cost and high adsorption efficiency, porous materials have become one of the most common materials to adsorb organic dyes and uptake CO2. Covalent organic frameworks (COFs), as a burgeoning class of crystalline porous polymers, present a promising application potential in many areas, such as gas adsorption and separation, heterogeneous catalysis, semiconductors and sensors due to their regular pores, modifiable frameworks, extensive specific areas and excellent stability. Especially the introduction of the functional groups to the skeleton of COFs provides abundant active sites to adsorb specific dyes and uptake gases. Inspired by this, we report a microporous COF (JUC-603, JUCJilin University China) decorated with sulfonic acid group. This COF was successfully synthesized through -ketoenamine based Michael addition-elimination reaction of 1,3,5-tris(3-dimethylamino-1-oxoprop-2-en-yl)benzene (TDOEB) and p-phenylenediamine (PPDA). A series of characterizations proved that JUC-603 had high crystallinity, opening microporous pore and excellent stability. Nitrogen adsorption-desorption isotherm revealed a high Brunauer-Emmett-Teller (BET) surface area (774 m 2 /g) and large pore size (1.6 nm). Moreover, we studied the adsorption of JUC-603 on dyes from aqueous solutions by ultravioletvisible spectrophotometry and the uptake capacity through CO2 adsorption-desorption. These results showed that JUC-603 could selectively adsorb cationic dyes such as crystal violet and methylene blue as well as uptake CO2 effectively (52 cm 3 /g at 273 K and 0.1 MPa). The ideal performance was attributed to the modulation of active sulfonic acid sites on the framework of JUC-603. This research thus indicates that the COF as a promising functionalized porous material has great potential in environmental remediation.