Improved porosity and CO2 capturing capacity in carboxyl enriched hyper-cross-linked polymers via side chain engineering of fluorene derivatives based building units

Microporous hyper-cross-linked polymers appending variant electron-withdrawing functional groups have enormous potential for selective CO 2 adsorption and separation, whereas these functionalities by lowering the charge density of monomers will decrease their reaction activity, which in turn is unfriendly for the direct and highly efficient preparation of polymers with high CO 2 uptake capacity. Herein a new amide “insertion” strategy for knitting polymers with ideal electron-withdrawing functionalities was advanced, and in this manner, a series of carboxyl enriched novel polymers were synthesized via the one-pot Friedel-Crafts alkylation reaction by using fluorene derivatives as emerging building blocks. The created polymer 3 possessing BET surface area 1947 m 2 g −1 have a CO 2 uptake of up to 20.03 wt% at 273.15 K/1.00 bar. Besides, the carboxyl and amide groups in structure could bestow the polymers an enhanced CO 2 /N 2 selectivity of 33.17 at 273.15 K. In addition, the hierarchical porosity and CO 2 adsorption capability of manufactured polymers can be intriguingly tailored, and prolonging the carboxylated side chains of building blocks by inserting different quantities of amide group will be propitious for bettering the porosity and CO 2 capturing capacity of manufactured polymers. Supported by charge density distribution simulation and electrostatic potential calculation, the peculiar changes in polymer structures and CO 2 adsorption features were also explained.