Alkali-Durable Covalent Organic Frameworks Carrying In Situ Ammonium as an Ionic Conductor toward Hydroxide Transport

Abstract

Durable transport of hydroxide ions is currently required to develop alkaline electrolyzers for efficient and clean hydrogen production. In the present work, a self-standing TAPA-TFP covalent organic framework (COF) membrane is obtained by oil–water interface polymerization. It is subsequently ionized through in situ ammonium groups via Menshutkin reactions to prepare a N+-COF ionic conductor. Based on the strategy of charge delocalization, the symmetric benzene around the in situ ammonium in the N+-COF ionic conductor could protect the cations from alkali degradation. Meanwhile, the micro-ordered alignment of cationic clusters endows the N+-COF ionic conductor with desirable hydroxide ion conductivities of up to 54 mS·cm–1 at 80 °C with an ion exchange capacity of 1.54 meq·g–1. Furthermore, when this N+-COF ionic conductor acts as a potential anion exchange membrane (AEM), it shows that water uptake and dimensional changes remain equalized between hydrophilicity and structural stability. It has been found that the N+-COF membrane has excellent alkaline stability through 1H nuclear magnetic resonance analysis, showing slight degradation of the cations after immersion in 1 M NaOH at 80 °C for 30 days. The alkaline stability and high conductivity of the N+-COF ionic conductor highlight its prospects as an AEM to be further applied in continuous water electrolysis, alkaline fuel cells, and hydrogen development.

Solar Carboxylation Using CO2: Interfacially Synthesized Flexible Covalent Organic Frameworks Film as a Photocatalyst for Highly Selective Solar Carboxylation of Arylamines with CO2

“…The formation of the C−N and C�O bonds confirmed the imine/β-ketoenamine linkage and tautomerization on Tp during the condensation reaction. 50 Moreover, the appearance of two characteristic peaks with binding energies of 871 and 853 eV corresponds to Ni 2p 1/2 and Ni 2p 3/2 , respectively, which suggested a 2+ oxidation state of nickel. 51,52 The appearance of new peaks of Ni and Cl in XPS (Figures 2 and S3 COFs film photocatalyst was found to be 6.77% based on inductively coupled plasma-atomic emission spectrometry analysis.…”

“…In addition, the N 1s and O 1s peaks at 397.6 and 529.6 eV are attributed to the C–N and CO bonds, respectively (Figure S3). The formation of the C–N and CO bonds confirmed the imine/β-ketoenamine linkage and tautomerization on Tp during the condensation reaction …”

Post-synthetic modification of covalent organic frameworks for CO2 electroreduction

“…These results indicate that the successful reduction of –C=N and the methylation with charge state changes. On the other hand, the FTIR and 13 C NMR results also reveal that the Menshutkin reaction is selective for the methylzation of C–N bonds rather than the co-exsited C=N bonds 60 .…”

“…Alternatively, the post-synthetic modification strategy provides a promising chance to construct functional skeletons, pores, and linkages at the molecular level with controllable catalytic properties [51][52][53][54][55][56] . Several single-step post-modifications were proposed to endow the base COFs with special properties [57][58][59][60] . Deng et al constructed imine-COFs by a postreduction method to improve gas diffusion on electrode 61 .…”