Pillared-layer MOFs

Host-Guest Reactions in Pillared-Layer MOFs. 133... 

Wang X-Y, Wang Z-M, Gao S (2007) A pillared layer MOF with anion-tunable magnetic properties and photochemical [2+2] cycloaddition. Chem Commun 11 1127-1129... 

To incorporate the metallosalen complex into the framework. Hupp and coworkers reported a micro-porous homochiral pillared-layer MOF as an highly effective enantioselective catalyst for olefin epoxidation. A solvothermal reaction between a chiral (salen)Mn complex (R,R)- -)-1,2-cyclohexanediamino-A,M -bis(3-... 

That the occurrence of expansion and contraction on guest removal depends on the nature of linkers is shown in two pillared-layer MOFs, [Cd(pzdc)(azpy)]-2H20 [32] and [Cd(pzdc)(bpee)]-1.5H20 [33] (Scheme 3). Here, Cd(pzdc) ... 

Figure 62 (a-f) Time- and concentration-dependent evolution of the intermediate phases during the formation of a flexible pillared-layer MOF [64]... 

Bdtard et al. [159] fabricated an MOF membrane by stepwise deposition of reactants. Two-pillared layered MOFs with the general formula [CujLjPJn (L = dicar-boxylate linker, P = pillaring ligand) were selected. For this demonstration, they selected the nonpolar [Cu2(ndc)2(dabco)] (1 ndc = 1,4-naphthalene dicarboxylate dabco = l,4-diazabicyclo(2.2.2)octane and the polar [Cu2(BME-bdc)2(dabco)] ) (2 BME-bdc = 2,5-bis(2-methoxyethoxy)-l,4-benzene dicarboxylate). The framework structure of 1 is shown in Figure 12.11. 

In addition to molecular sieving effects, which make use of different diffusivities of the different guests, the fine control over MOF surface chemistry has seen the emergence of materials that discriminate gases according to the strength of their adsorption interaction. An example here is the 3D pillared layer phase [Cu2(pzdc)2(pz)] (where... 

The pillared-layer stractures have been rather widely reported for MOFs, which are not interpenetrated because their relatively dense layers block one of the three dimensions. Based on a suitable layer structure containing coordinatively unsaturated... 

The term pillared-layer implies that the 3D structure is hierarchical with the layer formed first and the pillar coimects later, but such phenomena can be hardly observed directly since the self-assembly and crystallization of MOFs are generally carried out in a one-pot reaction. Nevertheless, using suitable non-bridging ligands instead of the pillar ligands, the individual single layer structure can be sometimes synthesized. In an occasional case, the hypothetic monolayer and pillared double layer have been isolated during the synthesis of a pUlared-layer MOF [73]. 

An opposite effect, that is, shrinkage of the framework on desolvation occurs in a neutral, microporous MOF [22] with a double-pillared-layer structure, where offset stacking of the layers generate channels. These channels are occupied by water molecules, which can be exchanged with MeOH or EtOH solvents at room temperature in SC-SC mode. The solvent molecules of the mother crystals can also be removed either by heating or under vacuum to produce the desolvated framework as stable crystals. While the guest-free structure experiences shrinkage, the unit-cell... 

Post-synthetic modification of double-piUared MOFs by [2+2] photo-cycloaddition was demonstrated in the following examples. Three photo-reactive double-pillared MOFs, [Zn2(bpe)2(muco)2]-DMF-H20 (44), [Zn2(bpe)2(bdc)2] DMF (45), and [Zn2(bpe)2 (fum)2]-H20 (46) (H2muco = trans,trans-macomc acid, H2bdc = 1,4-benzene dicarboxylic acid, and H2fum = fumaric acid), have been investigated [53]. In these stmctures, the layer is formed by the [Zn2(02C-C)4 SBU in which each... 

Fig. 27 A portion of the layer formed by Cd2(fumarate)2 (left) and the photo-reactive double-pillared MOF (47) right)...

Examples of dense silica, hybrid silica, metal oxides, solid-state metal oxide solutions, or colloidal self-assembly are unlimited. However, the recent developments to accurately control processing conditions (e.g., atmosphere, temperature, and motion) led to films with unique properties (see Figure 9.6) [52,53]. These progresses concern mesoporous coatings with controlled pore size and structure [26], hard template infiltration and/or replication [54-58], nanostructured epitaxial low-quartz thin films [59], ultrathin nanostructured supported networks [60,61], ultrathick porous Ti02 layer prepared from aqueous solutions [51], coatings with hierarchical porosity [62], multilayer porous stacks [63], colloidal MOF layers [64,65], pillar planar nanochannels (PPNs) for nanofluidics [66], and so on. 

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