Dual Strategic Approach to Prepare Defluorinated Triazole-Embedded Covalent Triazine Frameworks with High Gas Uptake Performance

Abstract

A dual strategic approach has been adopted via judicious design and synthesis of a new triazole-substituted perfluorinated aromatic nitrile (Tz-PFCN) building block to prepare three defluorinated triazole-embedded covalent triazine frameworks (Tz-df-CTFs) via ZnCl2-catalyzed ionothermal process for high capacity capture of small gases, especially CO2, H-2, and CH4. Our approach combines the incorporation of both thermally sacrificial fluorine functionality as the origin of abundant microporosity and multi-N-containing triazole functionality as strong CO2-philic unit into the building block, which integrates high surface area (up to 2106 m(2) g(-1)) and pore volume (up to 1.43 cm(3) g(-1)) largely dominated (>90%) by narrow- and ultra-micropores together with high nitrogen and oxygen heteroatom content in the resulted Tz-df-CTF materials. The high microporosity in Tz-df-CTFs is mainly generated through the in situ defluorination process of the perfluorinated Tz-PFCN building block during the ionothermal process, and pore surfaces embedded with CO2-philic basic N-active sites as both triazole and triazine moieties confer the frameworks with the highest amount of CO2 capture (7.65 mmol g(-1) at 273 K, 1 bar) and H-2 storage (2.91 wt % at 77 K, 1 bar) capability among all known porous organic polymers, including CTF systems, till date. The methane uptake capacity (4.41 wt % at 273 K, 1 bar) of these materials ranks second highest as well. A breakthrough simulation shows good separation of CO2/N-2 (flue gas composition) and CO2/CH4 binary gas mixture in Tz-df-CTFs under industrial fixed-bed operational conditions. We anticipate that this unique dual approach will allow new opportunities toward designing and synthesizing of novel high-performing nanoporous sorbents for task-specific applications in the domain of clean energy and environmental fields.