Pyrrole-Based Conjugated Microporous Polymers as Efficient Heterogeneous Catalysts for Knoevenagel Condensation.

Ruidong Gao,Yang Li,Long Chen,Guang Zhang,Fanli Lu

doi:10.3389/fchem.2021.687183

Abstract

Conjugated microporous polymers (CMPs) with robust architectures, facilely tunable pore sizes and large specific surface areas have emerged as an important class of porous materials due to their demonstrated prospects in various fields, e.g. gas storage/separation and heterogeneous catalysis. Herein, two new pyrrole-based CMPs with large specific surface areas and good stabilities were successfully prepared by one-step oxidative self-polycondensation of 1,2,4,5-tetra (pyrrol-2-ly)benzene or 1,3,5-tri (pyrrol-2-ly)benzene, respectively. Interestingly, both CMPs showed very high catalytic activity toward Knoevenagel condensation reaction, which was attributed to the inherent pore channels, high specific surface areas and abundant nitrogen sites within CMPs. Additionally, both CMPs displayed excellent recyclability with negligible degradation after 10 cycles. This work provides new possibilities into designing novel nitrogen-rich high-performance heterogeneous catalysts.

Highlights

Porous materials play significantly important roles in many fields of science and technology and have resurged with great popularity within last two decades
The structures of both conjugated microporous polymers (CMPs) were characterized by Fourier transform infrared (FT-IR) and solid-state 13C crosspolarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopies
The peaks at 1408 cm−1 for both CMPs are assignable to the stretching vibrations of -C C- in the aromatic rings (Svatos and Attygalle, 1997; Samran et al, 2004). 13CP-MAS NMR spectra display broad signals between 100 and 140 ppm, which are attributed to the carbon signals from pyrrole and benzene rings (Supplementary Figures S13, S14, ESI) and the positions of these peaks are in accordance with those of the monomers

Summary

INTRODUCTION

Porous materials play significantly important roles in many fields of science and technology and have resurged with great popularity within last two decades. On account of the many functions and broad prospects of pyrrole-based materials, it is interesting to develop new kind of pyrrolebased architectures and explore their properties and applications. In this respect, even though several porphyrinbased CMPs have been reported (Chen et al, 2010b; Modak et al, 2013; Liu et al, 2014; Xu et al, 2019; Zhu et al, 2020), to the best of our knowledge, pyrrole-based CMPs are very rare (Lee and Cooper, 2020). Both CMPs were synthesized by oxidative selfpolymerization within chloroform at room temperature (Supplementary, ESI)

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT