Zn,N co-doped 3D carbon frameworks constructed by in-situ polymerization-pyrolysis of fluid precursors and their applications in boosting atmospheric CO2 capture and fixation

Abstract

Through the rational design of 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([Bmim][NTf2])-based multi-component fluid precursors, we present a novel and sustainable strategy for preparing Zn,N co-doped 3D carbon frameworks (Zn@CTDPOP-IL) via in-situ polymerization-pyrolysis of fluid precursors, and explore their applications in atmospheric CO2 capture and clean conversion into cyclic carbonates. The structure and performance of Zn@CTDPOP-IL frameworks were optimized by preparing them under different pyrolysis temperatures and fluid precursor compositions. It was found that the in-situ polymerization of aldehyde and amine components in fluid precursors was crucial for achieving a high specific surface area of carbon frameworks; [Bmim][NTf2] was used as both the solvent and catalyst for in-situ polymerization, as well as the soft template agent during subsequent pyrolysis process. The carbon frameworks also possess multiple Lewis acid/base active sites, exhibiting excellent CO2 adsorption (3340 μmol/g) and conversion performance under mild (40 °C, 0.1 MPa) and solvent-free conditions. The cyclic carbonate yield reaches up to 94 % with a selectivity of 99 %, which is attributed to the superior activation abilities of Lewis acid/base sites towards epoxide and CO2 respectively. The reusability and universality of the catalyst were further investigated, revealing its exceptional structural stability and satisfactory versatility. Finally, we elucidated a proposed cycloaddition mechanism catalyzed by multiple active sites in Zn@CTDPOP-IL. Compared to other reported porous carbon materials, the Zn@CTDPOP-IL frameworks developed herein are simple and environmentally friendly in preparation while exhibiting excellent dual functionality for CO2 adsorption and catalytic conversion, making them highly promising for cleaner treatment of low-pressure waste CO2 resource.