Issue 41, 2023

Nano vs. bulk: surfactant-controlled photophysical and morphological features of luminescent lanthanide MOFs

Abstract

A surfactant-assisted bottom-up synthesis route provides access to nanoscale metal–organic frameworks (nMOFs) that exploit size-dependent property advantages. This includes an increased surface-to-volume ratio, improved dispersibility and superior morphological properties by a narrow size distribution compared to the bulk analogues. Photophysical properties such as photoluminescence are also influenced by particle size, surfactant components and post-synthetic modification. The series of the related organic linkers (H2bdc, H2bpdc and H2bpydc) together with trivalent lanthanides (Ln3+ = Eu3+, Tb3+) in synthesis and post-synthetic modification together with surface-active agents (CTAB, PVP) were used to assemble luminescent nMOFs for three archetype MOFs: nLn3+-bdc, nDUT-5:Ln3+ and nMOF-253:Ln3+. Both, dispersibility and morphology benefit from the CTAB- and PVP-controlled bottom-up particle downsizing down to 35 nm. DLS confirms homogeneous, narrow particle size distributions down to ±5 nm, which is 21-times smaller than the bulk analogues. Moreover, excellent luminescence QYs of up to 78.1(3)% were determined for the Ln3+-containing nMOFs. Successful post-synthetic modification with trivalent lanthanide ions of nMOFs was accomplished showing an improved photoluminescence sensitization effect compared to the bulk MOFs and exhibiting increased Ln3+-to-linker emission intensity ratios. The amount and photophysical properties of surfactants encapsulating the nMOFs were further quantified by DTA/TG-MS and UV-Vis-DRS. Finally, this work aims to elaborate thoroughly on the previously mentioned properties of nMOFs by comparison with their bulk analogues. Since surfactants play a key role in this synthesis route, the pros and cons of this approach were also assessed concerning several nMOF features.

Graphical abstract: Nano vs. bulk: surfactant-controlled photophysical and morphological features of luminescent lanthanide MOFs

Supplementary files

Article information

Article type
Paper
Submitted
30 avq 2023
Accepted
08 okt 2023
First published
09 okt 2023

J. Mater. Chem. A, 2023,11, 22478-22491

Nano vs. bulk: surfactant-controlled photophysical and morphological features of luminescent lanthanide MOFs

M. Maxeiner, L. Wittig, A. E. Sedykh, T. Kasper and K. Müller-Buschbaum, J. Mater. Chem. A, 2023, 11, 22478 DOI: 10.1039/D3TA05219B

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