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Hug, Stephan; Mesch, Maria B.; Oh, Hyunchul; Popp, Nadine; Hirscher, Michael; Senker, Jurgen; Lotsch, Bettina V. (2014): A fluorene based covalent triazine framework with high CO2 and H2 capture and storage capacities. In: Journal of Materials Chemistry A, Vol. 2, Nr. 16: S. 5928-5936
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Abstract

Porous organic polymers have come into focus recently for the capture and storage of postcombusted CO2. Covalent triazine frameworks (CTFs) constitute a nitrogen-rich subclass of porous polymers, which offers enhanced tunability and functionality combined with high chemical and thermal stability. In this work a new covalent triazine framework based on fluorene building blocks is presented, along with a comprehensive elucidation of its local structure, porosity, and capacity for CO2 capture and H2 storage. The framework is synthesized under ionothermal conditions at 300-600 degreeC using ZnCl2 as a Lewis acidic trimerization catalyst and reaction medium. Whereas the materials synthesized at lower temperatures mostly feature ultramicropores and moderate surface areas as probed by CO2 sorption (297 m2 g-1 at 300 degreeC){,} the porosity is significantly increased at higher synthesis temperatures{,} giving rise to surface areas in excess of 2800 m2 g-1. With a high fraction of micropores and a surface area of 1235 m2 g-1{,} the CTF obtained at 350 degreeC shows an excellent CO2 sorption capacity at 273 K (4.28 mmol g-1){,} which is one of the highest observed among all porous organic polymers. Additionally{,} the materials have CO2/N2 selectivities of up to 37. The hydrogen adsorption capacity of 4.36 wt% at 77 K and 20 bar is comparable to that of other POPs{,} yet the highest among all CTFs studied to date.