Host–Guest Chemistry in Boron Nitride Nanotubes: Interactions with Polyoxometalates and Mechanism of Encapsulation

Abstract

Boron nitride nanotubes (BNNTs) are an emerging class of molecular container offering new functionalities and possibilities for studying molecules at the nanoscale. Herein, BNNTs are demonstrated as highly effective nanocontainers for polyoxometalate (POM) molecules. The encapsulation of POMs within BNNTs occurs spontaneously at room temperature from an aqueous solution, leading to the self-assembly of a POM@BNNT host–guest system. Analysis of the interactions between the host-nanotube and guest-molecule indicate that Lewis acid–base interactions between WO groups of the POM (base) and B-atoms of the BNNT lattice (acid) likely play a major role in driving POM encapsulation, with photoactivated electron transfer from BNNTs to POMs in solution also contributing to the process. The transparent nature of the BNNT nanocontainer allows extensive investigation of the guest-molecules by photoluminescence, Raman, UV–vis absorption, and EPR spectroscopies. These studies revealed considerable energy and electron transfer processes between BNNTs and POMs, likely mediated via defect energy states of the BNNTs and resulting in the quenching of BNNT photoluminescence at room temperature, the emergence of new photoluminescence emissions at cryogenic temperatures (<100 K), a photochromic response, and paramagnetic signals from guest-POMs. These phenomena offer a fresh perspective on host–guest interactions at the nanoscale and open pathways for harvesting the functional properties of these hybrid systems.

A Series of POM–Viologen Photo-/Electrochromic Hybrids and Hydrogels Acting as Multifunctional Sensors for Detecting UV, Hg2+, and Organic Amines

“…POMs can transfer electrons while stabilizing their structures. Therefore, POMs can be applied in many fields such as optics, electrochemistry, catalysis, and magnetism. − Combining the advantages of viologen and POMs, we tried to construct POM-based viologen compounds with diversified structures and properties. The introduction of POMs as electron donors into a viologen system not only enhances the photochromic ability but also greatly increases the practical performance of viologen compounds.…”

A box-in-box supramolecular assembly for the highly selective recognition of natural, epigenetically and chemically modified cytosines in water

“…Supramolecular chemistry, characterized by excellent host–guest complexation abilities, emerged as a powerful tool for the encapsulation and separation of chemicals. 54 Metal–organic frameworks (MOFs), 55 covalent–organic frameworks (COFs), 56 macrocycles 57 and nanotubes 58 had all been applied for separation. Though cytosine and 5F-cytosine were reported to form a uniform solid, 59 the box-in-box supramolecular assembly 1 4+ ·SC4 4− was employed for their separation for the first time.…”

Anisotropic Growth of One-Dimensional Carbides in Single-Walled Carbon Nanotubes with Strong Interaction for Catalysis

“…One-dimensional heterostructures coupled with SWCNTs have attracted tremendous attention recently. − The use of CNTs as hosts has been widely demonstrated to encapsulate various guests in the cavity, such as molecules, − clusters, − picoperovskites, , and unusual atomic chains/crystals. ,− These fascinating findings have elaborately clarified the templating and shielding effects, allowing access to the unseen crystal structures ,, and dynamic events, ,,,− and improving electrical performance. − Moreover, the monolayer of graphite carbon of SWCNTs has also been proved to be transparent to the inner guests, which enables the guests to modulate the electronic surface structure of SWCNTs through host–guest charge communication. ,, However, the highly carbophilic metals such as W and Mo which tend to exhibit strong metal–carbon interactions , were rarely studied previously. The strong carbide-formatting elements (W, Mo) could exhibit strong interactions with carbon and result in a considerable charge communication with the host SWCNTs, providing a nondestructive way to homogeneously modify the electronic surface of SWCNTs.…”