Synthesis, structure, and fluorescence properties of a calcium-based metal-organic framework.

Daichi Kojima,Tomoe Sanada,Noriyuki Wada,Kazuo Kojima

doi:10.1039/c8ra06043f

Daichi Kojima, Tomoe Sanada + Show 2 more

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https://doi.org/10.1039/c8ra06043f

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Abstract

The solvothermal reaction of a mixture of calcium acetylacetonate and 1,4-naphthalenedicarboxylic acid (H2NDC) in a solution containing ethanol and distilled water gave rise to a metal–organic framework (MOF), {(H3O+)2[Ca(NDC)(C2H5O)(OH)]}4·1.1H2O. This MOF possesses a new structure composed of calcium clusters and H2NDC linker anions and shows a unique fluorescence property; it exhibits a fluorescence peak at 395 nm (λex = 350 nm) at room temperature, which is blue-shifted compared with that exhibited by the free H2NDC ligand. One of the possible mechanisms for this fluorescence is likely attributable to a ligand-to-metal charge transfer (LMCT) transition and is the first example of a calcium-based MOF exhibiting blue-shifted fluorescence due to LMCT.

Highlights

Many conventional metal-complex porous materials collapse upon removal of the guest molecules.[1]
Stable porous metal– organic frameworks (MOFs) composed of metal ions and organic linkers that do not collapse at room temperature were synthesized in the latter half of the 1990s,2,3 and subsequently there has been signi cant progress in the synthesis and functional analysis of porous materials
CaNDCMOF is monoclinic with the P21/n space group, and the formula of CaNDC-MOF was obtained as C56H48Ca4O24

Summary

Introduction

Many conventional metal-complex porous materials collapse upon removal of the guest molecules.[1]. Fluorescent MOFs hold promise as sensors for detecting gases and toxic substances because they show strong, controllable uorescence and have large surface areas with adjustable pore sizes.[16,17,18,19,20,21,22,23,24,25] MOFs exhibit good uorescence properties without requiring high temperature treatment because highly crystalline MOFs can be synthesized at relatively low temperatures.[26,27,28] Among them, it is known that MOFs with Ca or Mg show various luminescence in the range from UV to Vis under UV/Vis excitation. This MOF has a three-dimensional network structure with CaO8 coordination spheres composed of a calcium ion and carboxylates, and uoresces due to a ligandto-metal charge transfer (LMCT) transition

Experimental

Results and discussion

Conclusions