Phuong V. Dau

Synthesis, breathing, and gas sorption study of the first isoreticular mixed-linker phosphonate based metal–organic frameworks

The synthesis of the first water stable isoreticular phosphonate based mixed-linker metal-organic frameworks (MOFs) is achieved via the use of the N-donor heterocyclic co-ligands. Furthermore, these isoreticular phosphonate frameworks show selective CO(2)/N(2) uptake at low pressures.

Cyclometalated metal-organic frameworks as stable and reusable heterogeneous catalysts for allylic N-alkylation of amines.

Metal-organic frameworks (MOFs) functionalized via Ir(I) cyclometalation are shown to be effective as heterogeneous catalysts for the allylic N-alkylation of various amines. The MOF catalysts are one of the first and most effective MOF-based heterogeneous organometallic catalysts for the direct formation of C-N bonds. In addition, these MOFs represent a rare, stable and reusable, class of reactive Ir catalysts.

Metal–Organic Framework Regioisomers Based on Bifunctional Ligands†

Metal–organic frameworks (MOFs) are crystalline, hybrid materials that consist of inorganic connecting nodes and organic linker molecules. MOFs are attractive materials for applications in gas adsorption, separations, catalysis, and other technologies because of their high porosity, thermal stability, and chemical tunability. The ability to utilize different organic ligands in MOFs is particularly advantageous, as it allows for the introduction of a wider variety of functional groups into the pores of the MOF when compared to other porous, crystalline solids. The use of postsynthetic modification (PSM) has provided broader access to functional groups within MOFs. Both solvothermal and PSM routes have demonstrated that multifunctional or “multivariate” MOFs can be prepared, with more than one functional group displayed within the MOF pores. In these multifunctional MOF materials, the relative abundance of different ligands (and hence different functional groups) can be controlled, but not the distribution nor spatial orientation of the functional groups with respect to each other. To truly achieve the next level of tailored, multi-purpose materials, control over the relative position of different functional groups would be required. Herein, we describe the first class of bifunctional MOF “ligand regioisomers” and show that even these subtle changes can result in materials with dramatically different physical properties. Recently, framework isomers of MOFs have been classified into three major groups: interpenetrated, conformational, and orientation isomers—which all describe different structures comprised of the same ligand and metal ion composition. These isomers tend to have different properties from each other, albeit sometimes minor. MOFs derived from different ligands are referred to as “ligand-originated isomers”. Although many different ligands have been investigated for MOF formation, we are unaware of any systematic studies of ligand-originated isomers that arise from differences is regiochemical isomerism in a multifunctional ligand. In the studies presented here, the first MOF regioisomers are described and it is found that these regioisomers manifest themselves as distinct conformational isomers with notably different physical properties. Furthermore, these studies are the first to control the position of targeted functional groups in a porous, crystalline material. We chose a previously unreported class of bifunctional amino-halo benzene dicarboxylates (NH2X-BDC, where X = Cl, Br, or I) as the building blocks for MOF regioisomers. Independently, amino and halide groups are well-known in MOFs, 16] and PSM routes for both amino and halide groups have been reported, leaving open the possibility of PSM on MOF regioisomers. The target ligands were synthesized by halogenation of dimethyl-2-amino terephthalate (1) using Nhalosuccinimides (NCS, N-chlorosuccinimide; NBS, N-bromosuccinimide; NIS, N-iodosuccinimide; Table 1 and Scheme S1 in the Supporting Information). Depending on the N-halosuccinimide used, it was possible to obtain two different regioisomers that could be isolated by column chromatography. Electronic effects dictate that the orthoand para-positions, relative to the amino group, will be preferentially halogenated over the meta-position. In addition, steric considerations would suggest that the para-position might be more accessible than the ortho-position. Indeed, chlorination with NCS gave a nearly equal mixture of the ortho(2a) and

Site-selective cyclometalation of a metal–organic framework

Although porous materials, including metal–organic frameworks (MOFs), can be functionalized using heterogeneous reactions (solution–solid, gas–solid), there are no reports that modify chemically identical sites in a spatially selective, periodic fashion. Herein, the cyclometalation of two non-interpenetrated MOFs and an interpenetrated MOF in the solid state is reported using [Ir(COD)(OCH3)]2 and [Rh(COD)(Cl)]2 (COD = 1,5-cyclooctadiene). Incredibly, the cyclometalation of the interpenetrated MOF occurs only on ligands that lie along, one crystallographic axis, providing an unprecedented example of site-selective postsynthetic modification (PSM). This represents a degree of control on the functionalization of a porous, material that has not been otherwise realized, and is achieved in part because of the crystalline, periodic nature of MOFs. Furthermore, it was found that the degree of cyclometalation, increases the sorption capacity of the interpenetrated MOF.

A Bifunctional, Site-Isolated Metal–Organic Framework-Based Tandem Catalyst

Herein, we present the synthesis of a metal-organic framework-based tandem catalyst that contains two distinct catalytic domains. Zn(II)-based IRMOF-9-Irdcppy-NH2 (IRMOF = isoreticular metal-organic framework) has both organocatalytic amine and organometallic Ir(I) groups that were incorporated by both pre- and postsynthetic functionalization methods. The isolated amine and Ir(I) sites of IRMOF-9-Irdcppy-NH2 are shown to be independently catalytically active for performing a Knoevenagel condensation and allylic N-alkylation, respectively. More importantly, IRMOF-9-Irdcppy-NH2 can act as a tandem catalyst for both of these organic transformations in a one-pot reaction, which cannot be achieved efficiently using the combined, homogeneous analogues.

The influence of nitro groups on the topology and gas sorption property of extended Zn(II)-paddlewheel MOFs

The synthesis of three nitro-functionalized Zn(II)-paddlewheel based metal–organic frameworks (MOFs) and a Zn(II)-based 2D coordination polymer are reported. While 2-nitro-[1,1′-biphenyl]-4,4′-dicarboxylic acid (bpdc-NO2) is readily incorporated into structure of extended DMOF (DMOF = 1,4-diazabicyclo[2.2.2]octane MOF) and BMOF (BMOF = 4,4′-bipyridine MOF), 2,2′-dinitro-[1,1′-biphenyl]-4,4′-dicarboxylic acid (bpdc-[NO2]2) is only incorporated into the structure of BMOF. Furthermore, it is proposed that intermolecular interactions between the nitro groups influence the topology of these frameworks producing unexpected interpenetration in BMOF-1-bpdc-[NO2]2. Gas sorption studies of these functionalized frameworks also reveal effects of the nitro groups on topology as manifest in their gas sorption behaviour.