Sulfonate-Grafted Metal–Organic Frameworks for Reductive Functionalization of CO₂ to Benzimidazoles and N-Formamides

Abstract

Metal–organic frameworks (MOFs) with inner salt of 3-(pyridinylium)-1-propanesulfonate (PS) as the organic linkage were developed as catalysts (PS/MOFs) for reductive functionalization of carbon dioxide (CO2) to benzimidazoles and N-formamides. The pendant −SO3 – anion in the PS/MOFs acted as an organocatalytic active site for reductive cyclization of CO2 with 1,2-phenylenediamine to afford 1H-benzo­[d]­imidazole. A linear correlation was observed between the catalytic performance (in terms of turnover frequencies) and the specific surface area of PS/MOFs at a low conversion level of 1,2-phenylenediamine. Our theoretical investigation revealed significantly reduced energy barriers from 2.03 eV under catalyst-free conditions to 0.97 eV in the presence of the catalyst. The developed PS/MOFs can efficiently promote a broad range of benzimidazoles in 88–99% yields through reductive cyclization. Moreover, the PS/MOFs can readily catalyze N-formylation of various monoamines with CO2 as the carbonyl source for quantitative syntheses of N-formamides. The research thus highlights MOF-based catalysts for organocatalytic transformation of CO2 into high value-added chemicals.

Large-scale and solvent-free synthesis of magnetic bamboo-like nitrogen-doped carbon nanotubes with nickel active sites for photothermally driven CO2fixation

“…20,21 Since formamides are critical chemical intermediates in the production of drugs, agrochemicals, dyes, and fragrances, the preparation of C-N bonds is vitally valuable. 22,23 The synthesis of formamides by N-formylation of amines using CO 2 in the presence of reducing agents has been reported in the literature. 24 However, those reported for N-formylation catalysis are usually subject to harsh reaction conditions (high temperature or pressure) and inferior recoverability.…”

Bifunctional Metal‐free Heterogeneous Catalyst for the Synthesis of Methanol and Diols from CO2 and Epoxide

“…Finally the electron density of oxygen atom remove the Br − by S N 2 reaction to form cyclic carbonate. Again, the electron density over oxygen atom gives a facile attack towards silicon atom of hydrosilane as observed by Chen et al [40] . In PDVTA‐1‐SO 3 H, a nucleophilic attack from the oxygen atom towards silicon atom of triethylsilane resulted in the formation of a hypervalent silicon species and activate the silane.…”

“…After that the intermediate b reacts with CO 2 to form an intermediate c. Finally the electron density of oxygen atom remove the Br À by S N 2 reaction to form cyclic carbonate. Again, the electron density over oxygen atom gives a facile attack towards silicon atom of hydrosilane as observed by Chen et al [40] In PDVTA-1-SO 3 H, a nucleophilic attack from the oxygen atom towards silicon atom of triethylsilane resulted in the formation of a hypervalent silicon species and activate the silane. This activated silane reacts with the previously formed cyclic carbonate and gives the intermediate f via hydride transfer from silane.…”

Recent Scenario for the Synthesis of Benzimidazole Moiety(2020–2022)

“…The mechanism can be proceeded by three pathways according to the mechanistic hypothesis mentioned (scheme 17). [20] According to path a nucleophilic attack of the oxygen centre on PS toward the silicon centre on PhSiH 3 resulted in the formation of a hypervalent silicon species ( 17 b ). Direct transfer of activated organic hydride from 17b to CO 2 afforded silyl formate species ( 17 c ).…”