Nitrogen-Doped Carbons Derived from Imidazole-Based Cross-Linked Porous Organic Polymers.

Wojciech Kiciński,Sławomir Dyjak

doi:10.3390/molecules26030668

Wojciech Kiciński, Sławomir Dyjak

Open Access

https://doi.org/10.3390/molecules26030668

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Abstract

Nitrogen-doped and heteroatom multi-doped carbon materials are considered excellent metal-free catalysts, superior catalyst supports for transition metal particles and single metal atoms (single-atom catalysts), as well as efficient sorbents for gas- and liquid-phase substances. Acid-catalyzed sol–gel polycondensation of hydroxybenzenes with heterocyclic aldehydes yields cross-linked thermosetting resins in the form of porous organic polymers (i.e., organic gels). Depending on the utilized hydroxybenzene (e.g., phenol, resorcinol, phloroglucinol, etc.) and heterocyclic aldehyde variety of heteroatom-doped organic polymers can be produced. Upon pyrolysis, highly porous and heteroatom-doped carbons are obtained. Herein, polycondensation of phloroglucinol with imidazole-2-carboxaldehyde (and other, similar heterocyclic aldehydes with two heteroatoms in the aromatic ring) is utilized to obtain porous, N-doped organic and carbon gels with N-content of up to 16.5 and 12 wt.%, respectively. Utilization of a heterocyclic aldehyde with two different heteroatoms yields dually-doped carbon materials. Upon pyrolysis, the porous polymers yield ultramicroporous N-doped and N,S co-doped carbons with specific surface areas of up to 800 m2g−1. The influence of the initial composition of reactants and the pyrolysis temperature on the structure and chemical composition of the final doped organic and carbon materials is studied in detail.

Highlights

Heteroatom-doped carbon materials are considered more chemically active than their heteroatom-free counterparts
Nitrogen doping is especially common because it yields carbons with intrinsic metal-free catalytic properties and superb supports for carbon-supported transition metal catalysts, including metal nanoparticles, clusters, and single metal atoms/ions [1–4]
We have shown that sol–gel polycondensation of resorcinol and various heterocyclic aldehydes such as 2-pyrrolaldehyde, 2-thiophenaldehyde or 2-formylselenophene yields thermosetting organic gels doped and co-doped with N, S or Se heteroatoms [15,16]

Summary

Introduction

Heteroatom-doped carbon materials are considered more chemically active than their heteroatom-free counterparts. Nitrogen doping is especially common because it yields carbons with intrinsic metal-free catalytic properties and superb supports for carbon-supported transition metal catalysts, including metal nanoparticles, clusters, and single metal atoms/ions [1–4]. There are many methods to obtain porous carbons with heteroatom doping, including the utilization of biomass, ammonia treatment, ionic liquids, or synthetic polymeric precursors. Synthetic precursors such as metal organic frameworks allow better control of porosity and doping in comparison to natural feedstock [12]. Synthetic polymers allow the production of heteroatom-doped carbons of very specific characteristics, including a porous structure, morphology, and foreign atom doping type and position [13,14]. A whole range of heteroatom-doped porous carbons can be obtained from such organic polymers, with high yield

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