Photochemical reactivity of a lamellar lanthanum MOF

Abstract

A 2D lanthanum-dicarboxylate MOF of the formula ijLa 2 IJhex) 3 IJH 2 O) 6 ]Ĵ9H 2 O (H 2 hex = trans,trans-hexadiendioic acid or trans,trans-muconic acid) has been synthesized by the silica gel technique. The structure consists of metal-organic layers separated by a 2D network of water molecules. The metal-organic layers are made up of La 3+ arrays linked by the muconate ligands. Within a layer there is an infinite chain of short contacts between olefinic bonds allowing formation, upon UV irradiation, of three photoproducts.One of them was completely unexpected and its formation is explained by complex molecular movements in the solid state. The thermal instability of the MOF allowed isolation of five photochemically active lower hydrates. The rate constants of all hydrates were determined and show significant variations between them, attributable to structural rearrangements within the metal-organic layer brought about upon dehydration.

Synthesis of 2D and 3D MOFs with tuneable Lewis acidity from preformed 1D hybrid sub-domains

“…MOFs formed from Zn layers, through the use of liquid–liquid biphasic systems, and lamellar Cu-MOFs obtained by reduction of reactants through the use of solvent mixtures as a synthesis medium are other examples of 2D metal–organic structures. Very recently, specific organic spacers that act as growth inhibitors of 3D metal–organic structures, being directly coordinated to the inorganic nodes to build the final 2D hybrid material, have also been described 20–24. Furthermore, the importance of using specific organic linkers in metal–organic architectures has been explored for modulating the physico-chemical behaviour of MOFs, improving their reactivity and uptake capacity 31,32.…”

Solid State Packing and Photoreactivity of Alkali Metal Salts of trans,trans-Muconate

“…The proposed structures of C and D, as shown in the Figure 3, are in agreement with the observation of Michaelides et al in coordination polymers of muco. 28,29 The maximum percentages of the combined formation of C and D are about 5% and 10% respectively from 2 and 3. The formations of these minor products are inconsistent and could only be detected toward the end of the dimerization process (Figure 5), so their percentages are not accounted for in Figure 4.…”

“…However, in this work, infinitely aligned muco furnished cycloocta-3,7-diene-1,2,5,6-tetracarboxylate as the major product in a stepwise manner. Similarly, mixtures of products were observed from lanthanide coordination polymers of muco . − It is still not clear why a single [2 + 2] cycloaddition followed by Cope rearrangement was preferred over a direct [4 + 4] cycloaddition reaction or the double [2 + 2] cycloaddition reaction which can furnish a ladderane structure. The parameters that control the stepwise and concerted pathway to yield ladderane or cyclooctadiene derivative ( B ) are yet to be established.…”

“…Solid state photoreactivity of muconate has been reported before by Okada as organic salts and by Michaelides in coordination polymers. − Recently, we have shown the formation of the cyclooctadiene ring via concerted [4 + 4] cycloaddition reaction of muco in its gold­(I) macrocyclic complexes . Although photoreactive CC bonds have been successively aligned parallel for exhibiting solid state photoreactivity in discrete metal complexes, − coordination polymers, − and various types of organic salts ,,− and cocrystals, ,− the metal–organic salts have not been yet investigated extensively in this regard.…”

Functional Metal Organic Framework/SiO2 Nanocomposites: From Versatile Synthesis to Advanced Applications

“…Using a layer-by-layer process, Shekhah et al fabricated MOF films with mesoporous silica foam as a template to form highly crystalline HKUST-1 and ZIF-8, which showed high performance for gas separation [76]. Lanthanide MOF materials have great potential in the fields of luminescent dopants, solid-state lighting, integrated optics, optical communication, and solar cells [146]. In the lanthanide MOF/SiO 2 composite, lanthanide ions are connected to the Si–O network by covalent bonds, and the silica network provides uniform dispersion and luminescence stability for the lanthanide metal.…”