Fluorenone and Fluorenemalononitrile-Tethered Conjugated Microporous Polymers for Efficient CO2 Uptake and Rhodamine B Removal.

Herein, two conjugated microporous polymers (CMPs), TPET-FO and TPET-F2CN, are functionalized with carbonyl and nitrile groups. These porous networks are constructed via the Sonogashira coupling reaction, using 1,1,2,2-tetrakis(4-ethynylphenyl)ethene (TPET) as a tetrahedral core, which is coupled with 2,7-dibromo-9H-fluoren-9-one (FO-2Br) and 2-(2,7-dibromo-9H-fluoren-9-ylidene)malononitrile (FL-2CN-2Br), respectively. Both CMPs possess well-developed porosity, as evidenced by their Brunauer-Emmett-Teller surface areas (SBET) of 508 m2 g-1 for TPET-FO CMP and 682 m2 g-1 for TPET-F2CN CMP. Among the two materials, the TPET-F2CN CMP exhibits markedly superior performance. It demonstrates enhanced CO2 uptake capacities of 1.69 and 2.88 mmol g-1 at 298 and 273 K, respectively, significantly exceeding those of the TPET-FO CMP (0.96 and 1.60 mmol g-1 under identical conditions). In addition, TPET-F2CN CMP shows outstanding adsorption behavior toward rhodamine B (Rhd B), with an equilibrium adsorption capacity (qe) of 98.12 mg g- 1 and a maximum monolayer capacity (qm) of 155.6 mg g- 1, as determined by the Langmuir model. These values are substantially higher than those observed for TPET-FO CMP. Interaction Region Indicator (IRI) analysis indicated that the adsorption performance of TPET-F2CN CMP toward CO2 and Rhd B is mainly promoted by stronger non-covalent interactions and enhanced delocalization of π-electrons in TPET-F2CN CMP.