Quest for Highly Connected Metal–Organic Framework Platforms: Rare-Earth Polynuclear Clusters Versatility Meets Net Topology Needs

Abstract

Gaining control over the assembly of highly porous rare-earth (RE) based metal-organic frameworks (MOFs) remains challenging. Here we report the latest discoveries on our continuous quest for highly connected nets. The topological exploration based on the noncompatibility of a 12-connected RE polynuclear carboxylate-based cluster, points of extension matching the 12 vertices of the cuboctahedron (cuo), with 3-connected organic ligands led to the discovery of two fascinating and highly connected minimal edge-transitive nets, pek and aea. The reduced symmetry of the employed triangular tricarboxylate ligand, as compared to the prototype highly symmetrical 1,3,5-benzene(tris)benzoic acid guided the concurrent occurrence of nonanuclear [RE9(μ3-OH)12(μ3-O)2(O2C-)12] and hexanuclear [RE6(OH)8(O2C-)8] carboxylate-based clusters as 12-connected and 8-connected molecular building blocks in the structure of a 3-periodic pek-MOF based on a novel (3,8,12)-c trinodal net. The use of a tricarboxylate ligand with modified angles between carboxylate moieties led to the formation of a second MOF containing solely nonanuclear clusters and exhibiting once more a novel and a highly connected (3,12,12)-c trinodal net with aea topology. Notably, it is the first time that RE-MOFs with double six-membered ring (d6R) secondary building units are isolated, representing therefore a critical step forward toward the design of novel and highly coordinated materials using the supermolecular building layer approach while considering the d6Rs as building pillars. Lastly, the potential of these new MOFs for gas separation/storage was investigated by performing gas adsorption studies of various probe gas molecules over a wide range of pressures. Noticeably, pek-MOF-1 showed excellent volumetric CO2 and CH4 uptakes at high pressures.

Selective Gold Recovery and Catalysis in a Highly Flexible Methionine-Decorated Metal–Organic Framework

“…In the same way that other porous materials, 16,17 MOFs have proven their efficiency as vessels to capture and host small molecules, 18 and eventually, to separate mixtures of molecules according to their steric and stereochemical features as well as reactivity properties (functional substituent groups). [19][20][21][22] Despite the fact that a few examples of selective metal capture by MOFs have been reported, 23 to the best of our knowledge, the important recovery of Au has not been studied. Aiming at expanding the scope of application of MOFs and taking advantage of the well-known strong affinity of gold for sulfur derivatives, 24,25 we have focused our efforts on the rational design of bioMOFs showing functional channels decorated with thio-alkyl chains derived from the natural amino acid 26 L-methionine (Scheme S1).…”

Molecular Pivot‐Hinge Installation to Evolve Topology in Rare‐Earth Metal–Organic Frameworks

“…The aea-MOF-1 reported by Eddaoudi and coworkers is built from 12-connected RE 9 clusters and 3connected organic ligands (Figure 3a). [23] The aea net is constructed from 2D layers pillared by 12-c RE 9 clusters, where the 2D layers are composed of the nonanuclear clusters arranged in ahoneycomb (hcb)lattice pattern. The hcb layers are further intercalated by ap eriodic array of the 12connected RE 9 clusters in the aea net while they are directly pillared by the bent tetratopic linkers without the participation of secondary RE 9 clusters as pillars in the dfs net ( Figure 3b).…”

Lanthanide–Organic Frameworks Constructed from an Unsymmetrical Tricarboxylate for Selective Gas Adsorption and Small‐Molecule Sensing

“…[31,32] To further understand the adsorption properties, the isosteric heats of adsorption (Q st ) were calculated by using the Clausius-Clapeyron equation with the adsorption isotherms at 278, 288, and 298 K. As shown in Figure 3 (c), Ln-MOF 1 exhibited a higher heat of adsorption for CO 2 than for CH 4 . [33][34][35] The high heat of adsorption for CO 2 might be due to the higher polarity of CO 2 than that of CH 4 .…”