Accessing 14-Connected Nets: Continuous Breathing, Hydrophobic Rare-Earth Metal Organic Frameworks Based on 14-c Hexanuclear Clusters with High Affinity for Non-Polar Vapors

Abstract

Highly connected metal organic frameworks (MOFs) in which at least one building block has connectivity higher than twelve are very rare and much desirable. We report here the first examples of isostructural 14-connected MOFs, RE-frt-MOF-1, constructed from the assembly of 14-c hexanuclear rare-earth clusters, [RE6(μ3-X)8(COO)12]2– (RE: Y3+, Tb3+, Dy3+, Ho3+, Er3+, Yb3+ and X: OH–/F–) with a tritopic carboxylate-based organic linker. This linker serves as a 3-c and 4-c organic node resulting in the formation of a unique, trinodal (3,4,14)-c framework. RE-frt-MOF-1 are stable in air and alkaline aqueous solutions and show an intriguingly continuous, reversible breathing behavior, between a wide and a narrow-pore phase, upon guest removal. Crystallinity is retained during breathing, and single-crystal X-ray diffraction shed light into the associated structural transformation. Vapor sorption studies performed on Y-frt-MOF-1 revealed a high affinity for non-polar vapors such as n-hexane, cyclohexane, and benzene, displaying type I isotherms with high uptake at low relative pressures (<10–3 p/p 0), associated with the hydrophobic nature of the 1D channels and also with their rhombic shape. In contrast, polar vapors such as acetonitrile and ethanol show type V isotherms due to favorable vapor–vapor interactions. Notably these vapors, except cyclohexane, trigger the transition from the narrow to the wide pore phase, accompanied by a remarkable increase in uptake, reaching 70.6, 109, 100.4, and 87.7% for n-hexane, benzene, acetonitrile, and ethanol, respectively.

Lanthanide Metal–Organic Frameworks Exhibiting Fluoro-Bridged Extended Chains: Synthesis, Crystal Structures, and Magnetic Properties

“…A similar trend is found in the other four MOFs as shown in Tables and . Previously, several papers have indicated the possible presence of a mixed hydroxy-bridged and fluoro-bridged cluster. ,− The ratios found from EDS do not give any indication that there is a lack of fluorine due to replacement of fluorides with hydroxides in MOFs Ho-BPDC-2 , and Tb-BPDC-2 . Gd-BPDC-1 , Gd-BPDC-2 , and Tb-BPDC-1 show a minor deficiency in fluorine content, which indicates that some hydroxy/oxy bridges might be present.…”

“…The presence of a mixture of OH/F bridging found within these MOFs formed with 2-fba has been observed with other MOFs and appears to be dependent on the metal ion, linkers, and type of organofluorine modulator used. 24,31,46 Gas Adsorption. The pores of the MOFs were probed by using CO 2 and N 2 .…”

“…However, spectra of MOFs Tb-BPDC-1 , Ho-BPDC-2 , Gd-BPDC-2 , and Tb-BPDC-2 reveal a small peak between 525 and 530 eV that is indicative of M–O–M binding. The presence of a mixture of OH/F bridging found within these MOFs formed with 2-fba has been observed with other MOFs and appears to be dependent on the metal ion, linkers, and type of organofluorine modulator used. ,, …”

Synthesis of Fluoro-Bridged Ho3+ and Gd3+ 1,3,5-Tris(4-carboxyphenyl)benzene Metal–Organic Frameworks from Perfluoroalkyl Substances

“…It is proposed that the 2-FBA must first bind to the metal before the fluoride can be removed in solvents such as N , N ′-dimethylformamide (DMF), N , N ′-diethylformamide (DEF), or dimethylacetamide (DMAC). , A nucleophile such as dimethylamine (DMA) can then replace fluorine. , Recent publications on RE-based MOFs utilizing 2-FBA as a modulator have also shown the presence of μ 3 -OH/F bridges in a hexanuclear cluster based 2D MOF and μ 3 -O/F bridges in a Yb-based nonanuclear cluster. − In the present study, a dimeric complex formulated as bis­(2,2′-bipyridine)­tetrakis­(μ-2-fluorobenzoato- O , O ′)-bis­(2-fluorobenzoato)­diRE­(III) (RE = Ho 3+ and Gd 3+ ) 1 was prepared in water. The Ho version of 1 as well as the isostructural version with Sm 3+ were previously reported, both in an ethanolic solution. , Using water or an ethanolic solution as the solvent, the intact 2-FBA ions were bound to the rare-earth metals.…”

Encapsulation of cobaltocenium ions in a zeolite-like metal–organic framework

“…The applications of metal-organic frameworks (MOFs) have expanded into various fields including biomedical, 1-3 energy storage, [4][5][6] environmental, [7][8][9][10] sensors, [11][12][13][14] magnetism, [15][16][17] catalysis, [18][19][20] gas capture and storage, [21][22][23][24][25][26] etc. These applications depend in part on the discovery of new structures and methods.…”