Wonyoung Choe

A temperature-dependent, single crystal x-ray diffraction study of the giant magnetocaloric material, Gd5(Si2Ge2), across its Curie temperature (276 K) reveals that the simultaneous orthorhombic to monoclinic transition occurs by a shear mechanism in which the (Si, Ge)-(Si,Ge) dimers that are richer in Ge increase their distances by 0.859(3) A and lead to twinning. The structural transition changes the electronic structure, and provides an atomic-level model for the change in magnetic behavior w

We report the synthesis and characterization of porphyrin containing metal–organic frameworks that show high metal tunability without altering the framework topology.

Metal-organic framework (MOF) nanoparticles with high porosity and greater tunability have emerged as new drug delivery vehicles. However, premature drug release still remains a challenge in the MOF delivery system. Here, we report an enzyme-responsive, polymer-coated MOF gatekeeper system using hyaluronic acid (HA) and PCN-224 nanoMOF. The external surface of nanoMOF can be stably covered by HA through multivalent coordination bonding between the Zr cluster and carboxylic acid of HA, which acts

Metal organic polyhedra (MOPs) have potential as supramolecular building blocks, but utilizing MOPs for postsynthetic polymerization has not been explored. Although MOPs with flexible organic moieties have been recently reported to target enhanced processability, permanent porosity has not been demonstrated. Here, a novel synthetic strategy involving the cross-linking of MOPs <i>via</i> a covalent bond is demonstrated by exploiting a condensation reaction between the MOP and flexible organic lin

This highlight presents a review of porphyrin paddlewheel frameworks (PPFs) created using porphyrin metalloligands and paddlewheel secondary building units. The combination of these two components, along with dipyridyl pillaring linkers, results in the assembly of 25 PPFs. We describe the topology control exhibited in this series by considering the preferred coordination geometry of the porphyrin building blocks, the length and steric effects of the pillars, and the use of sequential self-assemb

The structure-electronic structure relationship of nonmetalated meso-tetraphenyl porphyrin (2H-TPP) on the (111) surfaces of Ag, Cu, and Au was studied with a combination of scanning tunneling microscopy, photoelectron spectroscopy, and density functional theory. We observe that the molecules form a 2D network on Ag(111), driven by attractive intermolecular interactions, while the surface migration barriers are comparatively small and the charge transfer to the adsorbed molecules is minimal. Thi

We report a hybrid solid system, UMOM-100-a and UMOM-100-b, synthesized by incorporation of Cu-based metal-organic polyhedra (MOPs) into a porous metal-organic framework (MOF) host, PCN-777. The MOP guests have acid (SO₃^-) functional groups, acting as functionalized nanocages, whereas the porosity is still maintained for proton conductivity. The key parameter for the UMOM-100 series is the number of MOPs inside a MOF, which controls the ratio between meso- and micropores, p

We present the sequential self-assembly of isoreticular bilayer metal–organic frameworks via a pillar insertion route. We also report the construction of a 3D framework from a 2D bilayer framework in an overall three-step self-assembly.

Metal-organic framework (MOF) nanoparticles have recently emerged as a promising vehicle for drug delivery with high porosity and feasibility. However, employing a MOF-based drug delivery system remains a challenge due to the difficulty in controlling interfaces of particles in a biological environment. In this paper, protein corona-blocked Zr₆ -based MOF (PCN-224) nanoparticles are presented for targeted cancer therapy with high efficiency. The unmodified PCN-224 surface is precoated

This perspective discusses the use of sequential self-assembly in the construction of metal-organic frameworks through the systematic insertion, replacement, and removal of organic structural building units. We review previous works that can be classified as such sequential self-assembly in multidimensional MOFs.

Five organic ligands of C3v and C2v symmetry, 3,5-bis(4-cyanophenylethynyl)cyanobenzene (1), 3,5-bis(4-cyanophenylethynyl)-4-methoxycyanobenzene (2), and 4,4‘-dicyanobenzophenone (3), cyanotris(4-cyanophenyl)methane (4), and tris(4-cyanophenyl)methanol (5), have been prepared, crystallized with silver(I) salts, and characterized by single-crystal X-ray study. Crystallographic data are as follows: [Ag·1·CF3SO3]·2C6H6, triclinic, P1̄ (no. 2), a = 10.0864(6) Å, b = 13.6029(10) Å, c = 13.8822(12) Å,

A novel metal–organic framework, [(Co(cis-ZnDCPP)(bpy)]·4DMF·H2O (cis-ZnDCPP = zinc 5,10-di(4-carboxyphenyl)-15,20-diphenylporphyrin; bpy = 4,4′-bipyridine; DMF = dimethyl formamide), has been synthesized from the solvothermal reaction and exhibits unique CdI2 layers constructed from paddle-wheel buiding units, Co2(COO)4, cis-ZnDCPP, and 4,4′-bipyridine linker.

The magnetocaloric material Gd5Si1.5Ge2.5 has been synthesized and its crystal structures at 292 and 163 K are reported from single-crystal X-ray diffraction experiments. At room temperature, orthorhombic Sm5Ge4-type and twinned, monoclinic Gd5Si2Ge2-type phases coexist in single crystal specimens. This phenomenon is mainly due to the covalent bond breaking and formation of (Si,Ge)−(Si,Ge) dimers during the crystallographic phase transition. We suggest an atomic-level model for the interface of