Coordination Polymers Based on a Biphenyl Tetraphosphonate Linker: Synthesis Control and Photoluminescence.

Ana D G Firmino,Duarte Ananias,Filipe A Almeida Paz,Jéssica S Barbosa,Ricardo F Mendes,João P C Tomé

doi:10.3390/molecules25081835

Abstract

In this work, we used the rigid tetrapodal organic linker, [1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid) (H8btp), for the preparation of two lanthanide–organic framework families of compounds: layered [Ln7(H5btp)4(H5.5btp)2(H6btp)2(H2O)12]∙23.5H2O∙MeOH [where Ln3+ = Eu3+ (1Eu) and Gd3+ (1Gd)], prepared using microwave-irradiation followed by slow evaporation; 3D [Ln4(H3btp)(H4btp)(H5btp)(H2O)8]∙3H2O [where Ln3+ = Ce3+ (2Ce), Pr3+ (2Pr), and Nd3+ (2Nd)], obtained from conventional hydro(solvo)thermal synthesis. It is shown that in this system, by carefully selecting the synthetic method and the metal centers, one can increase the dimensionality of the materials, also increasing structural robustness (particularly to the release of the various solvent molecules). Compound 1 is composed of 2D layers stacked on top of each other and maintained by weak π–π interactions, with each layer formed by discrete 1D organic cylinders stacked in a typical brick-wall-like fashion, with water molecules occupying the free space in-between cylinders. Compound 2, on the other hand, is a 3D structure with small channels filled with crystallization water molecules. A full solid-state characterization of 1 and 2 is presented (FT-IR spectroscopy, SEM microscopy, thermogravimetric studies, powder X-ray diffraction and thermodiffractometry). The photoluminescence of 1Eu was investigated.

Highlights

Metal-Organic Frameworks (MOFs), or Porous Coordination Polymers (PCPs), are a class of crystalline materials built from the coordination of organic linkers to metal ions or clusters [1]
While the main research regarding MOFs remains focused on materials derived from d-block metals coordinated to carboxylate-based organic linkers, our research group has focused on metal metals coordinated to carboxylate-based organic linkers, our research group has focused on metal phosphonates, lanthanide phosphonate-based MOFs (LnOFs)
1 reported followed an identical synthetic procedure, while trying to explore the structural effect when using smaller radii for the lanthanide cations: we note that in our past work photoluminescent materials were only obtained by doping an inert La3+ -based matrix

Summary

Introduction

Metal-Organic Frameworks (MOFs), or Porous Coordination Polymers (PCPs), are a class of crystalline materials built from the coordination of organic linkers to metal ions or clusters [1]. Molecules 2020, 25, 1835 shapes is one of the main features why these materials are good candidates for multiple applications in different research areas like gas storage and separation [3,4], catalysis [5,6], sensing [7,8,9,10,11], and different research areas like gas storage and separation [3,4], catalysis [5,6], sensing [7,8,9,10,11], and drug drug delivery [12,13], among others [14,15,16,17,18,19,20,21]. While the main research regarding MOFs remains focused on materials derived from d-block metals coordinated to carboxylate-based organic linkers, our research group has focused on metal metals coordinated to carboxylate-based organic linkers, our research group has focused on metal phosphonates, lanthanide phosphonate-based MOFs (LnOFs). Wang and co-workers were able to improve the DNA sensing of LnOF nanosheets by simple change

Methods

Results

Conclusion