Metal and Co‐Catalyst Free CO₂ Conversion with a Bifunctional Covalent Organic Framework (COF)

Abstract

The excessive growth of CO 2 brings about the global warming and subsequent climate change, which is an increased public concern issue. Currently, the chemical fixation of CO 2 is identified as one of the most effective approaches to reduce and utilize CO 2. Thus, it is a great challenge to rationally design and construct high-efficient catalysts for CO 2 conversion and utilization. Here, a unique metal-free bifunctional COF heterogeneous catalyst was successfully achieved via the post-modified strategy, which simultaneously bears À COOH as Brønsted acidic center and Br À ion as nucleophilic active site. By virtue of abundant porosity, excellent stability, favorable CO 2 adsorption, and dual catalytic sites, this material can efficiently facilitate the coupling reaction of CO 2 with epoxide to form cyclic carbonate without co-catalyst under mild conditions. Moreover, it has excellent reusability, without significant reduction of the catalytic activity after at least five cycles.

Facile Grafting of Imidazolium Salt in Covalent Organic Frameworks with Enhanced Catalytic Activity for CO2 Fixation and the Knoevenagel Reaction

“…Based on the previous studies of CO 2 cycloaddition catalyzed by IL, − optimization of the pathway catalyzed by H 3 N + –R + Br – was performed following the most probable three-step mechanism: epoxide activation, CO 2 insertion, and intramolecular cyclization. The Gibbs free-energy profiles and the structures of transition states involving structure A or structure B are illustrated in Figures and S9, respectively.…”

A study of contemporary progress relating to COF materials for CO2capture and fixation reactions

“…This unique bi-functional COF has both active nucleophilic sites and Brønsted acid catalytic sites. 22 The research group synthesized TpPa-Py COF via treating 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, 2,5-diaminopyridine, 1,4-dioxane, mesitylene, and aqueous acetic acid (6 M) in a sealed Pyrex pressure tube at 120 °C for three days. After that, they treated COF-TpPa-Py with a solution of saturated Br–CH 2 COOH under a N 2 atmosphere for one day at 70 °C and finally obtained TpPa-Py-Br − -COF.…”

Metal-assisted synthesis of salen-based porous organic polymer for highly efficient fixation of CO2 into cyclic carbonates

“…31,32 However, most of the heterogeneous catalysts currently used for the cycloaddition of CO 2 require a long reaction time, which is not conducive to their development for industrial use. 21,33–35 As a consequence, the search continues for highly efficient heterogeneous catalytic systems for the preparation of cyclic carbonates under mild conditions.…”