New nitrogen-rich azo-bridged porphyrin conjugated microporous networks for high performance of gas capture and storage

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Jianjun Wei, Associate Professor (Creator)
The University of North Carolina at Greensboro (UNCG )
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Abstract: A series of new conjugated microporous polymers (Azo-1, Azo-2 and Azo-3) based on a nitrogen-rich porphyrin building unit and an azo bond linkage were synthesized by KOH assisted condensation. These materials were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C NMR, XPS, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and tested for gas (N2, CO2 and H2) adsorption. It was revealed that the azos presented the formation of porous polymer networks affording amorphous particles with rough surfaces and irregular morphology with excellent thermal stability under nitrogen conditions. The Brunauer–Emmett–Teller (BET) model of the N2 adsorption gave apparent surface area ranges of 520–675 m2 g-1. The results from non-local density functional theory (NL-DFT) calculations suggested a pore size distribution between 1.6 and 4.0 nm. The gas (CO2, H2) adsorption isotherms demonstrated outstanding CO2 uptake up to 17.5 wt% (3.98 mmol g-1 for Azo-2) and moderate H2 storage. The isosteric heats of adsorption (Qst) are high, with values of 36–37 kJ mol-1 for the azo polymers. Moreover, the azo-polymer networks exhibited excellent selectivity with CO2/N2 up to 64.3 for Azo-2 at 273 K/1 bar. It was suggested that the nitrogen-rich active sites of the polymers play an important role for CO2 capture and storage.

Additional Information

RSC Advances, 2016, 6 (36), 30048-30055
Language: English
Date: 2016
conjugated microporous polymers, azo polymers, carbon capture

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