Issue 11, 2017

Orthogonal self-assembly of a trigonal triptycene triacid: signaling of exfoliation of porous 2D metal–organic layers by fluorescence and selective CO2 capture by the hydrogen-bonded MOF

Abstract

Trigonal 3-connecting imidazole-annulated triptycene triacid (H3TPA) is a molecular module that is programmed for orthogonal self-assembly. Upon treatment with metal salts such as CoCl2, Mn(NO3)2, Zn(NO3)2 and Cd(NO3)2, highly porous isostructural MOFs are obtained in which the TPA linker undergoes metal–ligand coordination and hydrogen bonding through carboxylate groups and imidazole moieties, respectively. The MOFs are constructed by hydrogen bond-mediated offset stacking of porous (3,3) honeycomb layers formed by the self-assembly of TPA with 3-connecting triangular bimetallic SBUs. We show that the interlayer hydrogen bonds can be disrupted by solvents such as DMSO, leading to solvent-induced delamination of 2D metal–organic nanosheets. The delamination is signaled by turn-on of fluorescence, which is suppressed in the bulk state. Indeed, the extent of exfoliation with different solvents – as reflected from fluorescence quantum yields as well as solvent-induced shifts in emission maxima – can be nicely correlated with Gutmann's solvent DN numbers, which are a measure of the ability of solvents to accept hydrogens in hydrogen bonds. The results demonstrate how the bulk materials with layered structures can be (i) engineered in a ‘bottom-up’ approach by orthogonal self-assembly of an organic linker created by de novo design and (ii) in turn be exfoliated in a ‘top-down’ approach by solvent-induced ultrasonication. As bulk materials, the hydrogen-bonded MOFs lend themselves to selective as well as high adsorption of CO2 under ambient conditions as a result of the nitrogenous environment of pores conferred by the benzimidazole moieties.

Graphical abstract: Orthogonal self-assembly of a trigonal triptycene triacid: signaling of exfoliation of porous 2D metal–organic layers by fluorescence and selective CO2 capture by the hydrogen-bonded MOF

Supplementary files

Article information

Article type
Paper
Submitted
26 Dec 2016
Accepted
07 Feb 2017
First published
07 Feb 2017

J. Mater. Chem. A, 2017,5, 5402-5412

Orthogonal self-assembly of a trigonal triptycene triacid: signaling of exfoliation of porous 2D metal–organic layers by fluorescence and selective CO2 capture by the hydrogen-bonded MOF

P. Chandrasekhar, A. Mukhopadhyay, G. Savitha and J. N. Moorthy, J. Mater. Chem. A, 2017, 5, 5402 DOI: 10.1039/C6TA11110F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements