Sustainable synthesis of multifunctional porous metalloporphyrin polymers for efficient carbon dioxide transformation under mild conditions

Multifunctionalization of porous organic polymers (POPs) for working in concert on a substrate is now a research topic in CO 2 catalysis, yet it remains challenging. This work describes a pre- and post-synthetic strategy to design metalloporphyrin-based azo-hierarchical porous ionic polymers (ZnTPP/QA-azo-PiPs), which were synthesized based on diazo-coupling reaction of tetra(4-aminophenyl) porphyrin zinc with tri/diphenols in aqueous solution under mild conditions, followed by etherification with quaternary ammonium bromide. This synthetic approach endows ZnTPP/QA-azo-PiP 1 with features of an improved surface area (181 m 2 /g), hierarchical porosity, and high-density active sites. ZnTPP/QA-azo-PiP 1 presented a noteworthy CO 2 uptake of 1.77 mmol/g at 273 K and 1.0 bar and good CO 2 /N 2 selectivity of 44.8. As expected, ZnTPP/QA-azo-PiP 1 showed quantitative conversion and selectivity for a range of epoxides under mild conditions (1.0 MPa, 80 °C, 12 h) in the CO 2 cycloaddition reaction. ZnTPP/QA-azo-PiP 1 could been recycled easily and retained complete retention of activity and selectivity for over 7 cycles. Moreover, with efficacious activity in conversion of diluted CO 2 (15% CO 2 in 85% N 2 , v/v), ZnTPP/QA-azo-PiP 1 could smoothly catalyze CO 2 -involved reaction to produce oxazolidinones and N-formylated amines under mild conditions. This work promotes sustainable synthesis of advanced multifunctional POPs and gives great promise for their application in synthetic transformations of CO 2 .