Thermosensitive and Drug-Loaded Ordered Mesoporous Silica: A Direct and Effective Synthesis Using PEO‑<i>b</i>‑PNIPAM Block Copolymers

An ecofriendly and straightforward approach to prepare PNIPAM-functionalized mesoporous hybrid silica materials is described: the use of PEO-<i>b</i>-PNIPAM diblock copolymers, specifically designed to act as efficient structure-directing agents (SDA) in silica synthesis, led directly to functionalized hybrid silica materials, whose mesoporosity was subsequently created by washing the material in water in appropriate conditions. Drug-loaded mesoporous silica materials are usually obtained by impregnating such hybrid materials in a drug-containing organic solvent. To avoid such a step, an alternative strategy for the direct incorporation of a hydrophobic drug (i.e., during the synthesis of the hybrid material) was successfully attempted. Finally, the effect of temperature on the release rate of the drug, which appears to be quite slow, was investigated

Diffusion-Coupled Molecular Assembly: Structuring of Coordination Polymers Across Multiple Length Scales

Porous coordination polymers (PCPs) are an intriguing class of molecular-based materials because of the designability of framework scaffolds, pore sizes and pore surface functionalities. Besides the structural designability at the molecular scale, the structuring of PCPs into mesoscopic/macroscopic morphologies has attracted much attention due to the significance for the practical applications. The structuring of PCPs at the mesoscopic/macroscopic scale has been so far demonstrated by the spatial localization of coordination reactions on the surface of templates or at the phase boundaries. However, these methodologies have never been applied to the fabrication of solid-solution or multivariate metal–organic frameworks (MOFs), in which multiple components are homogeneously mixed. Herein, we demonstrate the structuring of a box-type superstructure comprising of a solid-solution PCP by integrating a bidirectional diffusion of multiple organic ligands into molecular assembly. The parent crystals of [Zn₂(ndc)₂(bpy)]_<i>n</i> were placed in the DMF solution of additional organic component of H₂bdc, and the temperature was rapidly elevated up to 80 °C (ndc = 1,4-naphthalenedicarboxylate, bpy = 4,4′-bipyridyl, bdc = 1,4-benzenedicarboxylate). The dissolution of the parent crystals induced the outward diffusion of components; contrariwise, the accumulation of the other organic ligand of H₂bdc induced the inward diffusion toward the surface of the parent crystals. This bidirectional diffusion of multiple components spatially localized the recrystallization at the surface of cuboid parent crystals; therefore, the nanocrystals of a solid-solution PCP ([Zn₂(bdc)_1.5(ndc)_0.5(bpy)]_<i>n</i>) were organized into a mesoscopic box superstructure. Furthermore, we demonstrated that the box superstructures enhanced the mass transfer kinetics for the separation of hydrocarbons

Integration of Porous Coordination Polymers and Gold Nanorods into Core–Shell Mesoscopic Composites toward Light-Induced Molecular Release

Besides conventional approaches for regulating in-coming molecules for gas storage, separation, or molecular sensing, the control of molecular release from the pores is a prerequisite for extending the range of their application, such as drug delivery. Herein, we report the fabrication of a new porous coordination polymer (PCP)-based composite consisting of a gold nanorod (GNR) used as an optical switch and PCP crystals for controlled molecular release using light irradiation as an external trigger. The delicate core–shell structures of this new platform, composed of an individual GNR core and an aluminum-based PCP shell, were achieved by the selective deposition of an aluminum precursor onto the surface of GNR followed by the replication of the precursor into aluminum-based PCPs. The mesoscopic structure was characterized by electron microscopy, energy dispersive X-ray elemental mapping, and sorption experiments. Combination at the nanoscale of the high storage capacity of PCPs with the photothermal properties of GNRs resulted in the implementation of unique motion-induced molecular release, triggered by the highly efficient conversion of optical energy into heat that occurs when the GNRs are irradiated into their plasmon band. Temporal control of the molecular release was demonstrated with anthracene as a guest molecule and fluorescent probe by means of fluorescence spectroscopy