Yohei Takashima

Molecular decoding using luminescence from an entangled porous framework

Chemosensors detect a single target molecule from among several molecules, but cannot differentiate targets from one another. In this study, we report a molecular decoding strategy in which a single host domain accommodates a class of molecules and distinguishes between them with a corresponding readout. We synthesized the decoding host by embedding naphthalenediimide into the scaffold of an entangled porous framework that exhibited structural dynamics due to the dislocation of two chemically non-interconnected frameworks. An intense turn-on emission was observed on incorporation of a class of aromatic compounds, and the resulting luminescent colour was dependent on the chemical substituent of the aromatic guest. This unprecedented chemoresponsive, multicolour luminescence originates from an enhanced naphthalenediimide–aromatic guest interaction because of the induced-fit structural transformation of the entangled framework. We demonstrate that the cooperative structural transition in mesoscopic crystal domains results in a nonlinear sensor response to the guest concentration. Distinguishing closely related molecules using chemosensor materials is a continuing challenge. Here, an entangled porous coordination polymer is developed, which confines volatile organic compounds, and allows photoluminescence-based distinction of structurally similar aromatic molecules.

Nanoporous Nanorods Fabricated by Coordination Modulation and Oriented Attachment Growth

A growing attachment: Porous coordination polymer (PCP) nanorods are synthesized by modulation of the coordination equilibria between framework components, which regulates the rate of framework extension and crystal growth. Investigation of the crystal growth mechanism by TEM indicates that face-selective modulation on the surfaces of PCP crystals enhances the anisotropic crystal growth of nanorods by an oriented attachment mechanism.

Heterogeneously Hybridized Porous Coordination Polymer Crystals: Fabrication of Heterometallic Core–Shell Single Crystals with an In-Plane Rotational Epitaxial Relationship†

MOF on MOF: Core-shell porous coordination polymer (PCP) crystals are fabricated at the single-crystal level by epitaxial growth in solution. Synchrotron X-ray diffraction measurements unveiled the structural relationship between the shell crystal and the core crystal, where in-plane rotational epitaxial growth compensates the difference in lattice constant.

Porous coordination polymer with pyridinium cationic surface, [Zn(2)(tpa)(2)(cpb)].

We have synthesized a porous coordination polymer containing a pyridinium cation as an organic linker and have investigated the methanol absorptive ability of the pyridinium cationic surface. The result implies that the pyridinium cationic surface participates in the strong adsorption of methanol.

Control of the charge-transfer interaction between a flexible porous coordination host and aromatic guests by framework isomerism

Based on 2,5-thiophenedicarboxylate (thdc), two isomorphic frameworks, [Zn(thdc)(dpNDI)]n, are assembled from zinc ions and N,N′-di(4-pyridyl)-1,4,5,8-naphthalenediimide (dpNDI). Because of the significant difference in their porous structures, these isomers show different charge-transfer interactions with electron-donating aromatic molecules.

Control over the nucleation process determines the framework topology of porous coordination polymers

In this contribution, we present a method to selectively synthesize crystal polymorphs of [Zn2(bdc)2(dabco)]n (1) and [Zn2(bdc)2(bpy)]n (2), either the pillared 2D square-grid nets (1sql or 2sql) or the pillared 2D Kagome nets (1kgm or 2kgm) by simply changing the crystallization temperature.

Enhanced Phosphorescence Emission by Incorporating Aromatic Halides into an Entangled Coordination Framework Based on Naphthalenediimide

Phosphorescence emission at room temperature is turned on in an entangled porous coordination polymer (PCP) with naphthalenediimide (NDI) as chromophore, by incorporating halogenated guests into the pores. The phosphorescent efficiency is drastically increased by the incorporation of aromatic halide guests in comparison with the incorporation of nonaromatic derivatives. Aromatic halide guests trigger a structural transformation, which allows a strong interaction with the NDI ligand in the framework through charge-transfer complexation, and provides an extra population process of the triplet state. The long-lived photoinduced triplet states, with an emission wavelength in the red region of the visible spectrum, demonstrated by this PCP, may open the door for potential uses, for example, as singlet-oxygen generators or for bio-imaging applications.

Thermodynamically controlled coordination-engineering of novel 2D cadmium thiolate coordination polymers

Reaction of Cd(OAc)2·2H2O with 4,4′-biphenyldithiol (H2bpdt) in different alkyldiamines at 105 °C gave single crystals of different 2D-layered cadmium thiolates metal–organic frameworks. The alkyldiamine acts both as a solvent and as a coordination-engineering agent to control the crystal growth and the dimensionality of the cadmium thiolate networks.