Melamine sponge-based copper-organic framework (Cu-CPP) as a multi-functional filter for air purifiers.

COVID-19 has drawn great attention on the necessity for establishing pathogen-free indoor air. This paper offers an insight into the potential application of a multi-purpose filter to remove fine particulates and disinfect pathogens using melamine sponge with a copper-organic framework. In-situ growth dip coating method was applied to coat Cu-based coordination polymer particle (Cu-CPP) on melamine sponge (MS). The integration of Cu-CPPs with high crystallinity and highly active surface area (1,318.1 m2/g) enabled Cu-CPP/MS to have an excellent capture rate (99.66%) and an instant disinfection rate of 99.54% for Escherichia coli. Electrostatic attraction seemed to play a crucial role in capturing negative-charged pathogens effectively by positive charges on Cu-CPP arising from unbalanced copper ions in Cu-CPP. Disinfection of pathogens was mainly attributed to catalytically active Cu2+ sites. Organic ligand played an important role in bridging and maintaining Cu2+ ions within the framework. This study highlights the design of a new capture-and-disinfection (CDS) air filter system for pathogens using Cu-CPP/MS. It can be applied as a substitute for conventional high-efficiency particulate air (HEPA) filters. Electronic Supplementary Material: Supplementary material is available for this article at 10.1007/s11814-021-1000-4 and is accessible for authorized users.

Self-Healing Graphene-Templated Platinum-Nickel Oxide Heterostructures for Overall Water Splitting.

Electrocatalysts with dramatically enhanced water splitting efficiency, derived from controlled structures, phase transitions, functional activation, etc., have been developed recently. Herein, we report an in situ observation of graphene-based self-healing, in which this functional activation is induced by a redox reaction. Specifically, graphene on stainless steel (SUS) switches between graphene (C-C) and graphene oxide (C-O) coordination via an electrical redox reaction to activate water splitting. A heterostructure comprising Pt-NiO thin films on single-layer graphene directly grown on a SUS substrate (Pt-NiO/Gr-SUS) was also synthesized by electrodeposition. Pt-NiO/Gr-SUS exhibited water splitting activity with low Pt loading (<1 wt %). The findings provide valuable insight for designing robust electrodes based on reversible redox-induced self-healable graphene to develop more efficient catalysts.

Pd Nanocluster/Monolayer MoS2 Heterojunctions for Light-Induced Room-Temperature Hydrogen Sensing.

Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. In this study, heterostructures composed of monolayer MoS2 and Pd nanoclusters (Pd/MoS2) acting as photo- and hydrogen-sensitizers are successfully fabricated in a facile and scalable manner. The uniform deposition of morphologically isotropic Pd nanoclusters (11.5 ± 2.2 nm) on monolayer MoS2 produces a plethora of active heterojunctions, effectively suppressing charge carrier recombination under light illumination. The dual photo- and hydrogen-sensitizing functionality of Pd/MoS2 can enable its use as an active sensing layer in optoelectronic hydrogen sensors. Gas-sensing examinations reveal that the sensing performance of Pd/MoS2 is enhanced three-fold under visible light illumination (17% for 140 ppm of H2) in comparison with dark light (5% for 140 ppm of H2). Photoactivation is also found to enable excellent sensing reversibility and reproducibility in the obtained sensor. As a proof-of-concept, the integration of Pd nanoclusters and monolayer MoS2 can open a new avenue for light-induced hydrogen gas sensing at room temperature.

Metal-Ion Tuning in Triple-Stranded Helicate-Based Metallosupramolecules.

Effective incorporation of multiple types of ligands in a given coordination structure provides structural complexity and functional diversity to the resultant coordination-driven assembly. One of the most widely used synthetic approaches is the utilization of the molecular symmetry principle to combine multiple ligands and specific metallic centers in a preferred manner. The variation of metal ions can be helpful to understand the importance of symmetry for the generation of structurally hierarchical supramolecular platforms. We describe the synthesis and characterization of isostructural supramolecular helicates, [M8 (PDA)6 (AIP)3 (DMF)6-x (H2 O)x ] (M=Ni (1), Co (2), and Mn (3); PDA=2,6-pyridinedicarboxylate; AIP=5-aminoisophthalate; x=0 for 1, and x=4 for 2 and 3). The effect of metal variation on the formation of supramolecular helicates and their solid-state crystal packing are discussed. Despite the disparity in the ionic radii and distinct coordination-geometry preferences of Co2+ , Ni2+ , and Mn2+ , all metal centers engaged in the assembly with the heteroleptic ligands in the same manner to form isostructural supramolecular helicates.

Controllable Synthesis of a Highly Ordered Polymeric Structure Assembled from Cobalt-Cluster-based Racemic Supramolecules.

Metallosupramolecule-based polymeric platforms with high degrees of hierarchy and tailorable functionalities are of great interests because of their unique morphologies and potential applications. Herein, the controllable synthesis of a highly-ordered polymeric structure, {[M,P-Co8 (PDA)6 (HIP)3 (DMF)5 (H2 O)]3 -[Co(DMF)(H2 O)2 ]} (1) (PDA=2,6-pyridinedicarboxylate, HIP=5-hydroxyisophthalate, DMF=dimethylformamide) with unique topology is reported. The solid-state structure of 1 reveals that it is alternately and periodically assembled from racemic supramolecular monomers to form a zigzag-shaped polymeric strand. Discrete racemic supramolecules (2) with topologies similar to those of monomeric species of 1 are also controllably synthesized in a separate reaction. Formation of intermolecular hydrogen bonds between supramolecules associated with hydroxyl groups of HIPs are critical for the unique solid-state packing geometries of 1 and 2.

Cage-like crystal packing through metallocavitands within a cobalt cluster-based supramolecular assembly.

A cobalt (Co) supramolecular triple-stranded helicate, [Co8(PDA)6(Br-PTA)3(DMF)4(H2O)2] (1) (PDA = 2,6-pyridinedicarboxylate, Br-PTA = 5-bromoisophthalate, DMF = dimethylformamide), is successfully synthesized and fully characterized. The solid-state structure of 1 shows that four cobalt atoms are coordinated by three PDA ligands to form a tetranuclear cobalt cluster with three extension points and the ditopic Br-PTA ligands interlink two basic assembly units. In crystal packing, the bromo group is surrounded by the cavity-like tetranuclear cobalt cluster, which acts as a metallocavitand, to generate a unique cage-like crystal packing geometry. The isomorphous molecular cage, which exhibits a similar crystal-packing geometry as observed in 1, is also successfully isolated. This is an unusual example of a highly symmetric cage-like crystal packing architecture, resulting from the interaction among metallocavitands of in situ generated supramolecular modules.

A Cobalt Supramolecular Triple-Stranded Helicate-based Discrete Molecular Cage.

We report a strategy to achieve a discrete cage molecule featuring a high level of structural hierarchy through a multiple-assembly process. A cobalt (Co) supramolecular triple-stranded helicate (Co-TSH)-based discrete molecular cage (1) is successfully synthesized and fully characterized. The solid-state structure of 1 shows that it is composed of six triple-stranded helicates interconnected by four linking cobalt species. This is an unusual example of a highly symmetric cage architecture resulting from the coordination-driven assembly of metallosupramolecular modules. The molecular cage 1 shows much higher CO2 uptake properties and selectivity compared with the separate supramolecular modules (Co-TSH, complex 2) and other molecular platforms.

Nano Metal-Organic Framework-Derived Inorganic Hybrid Nanomaterials: Synthetic Strategies and Applications.

Nano- (or micro-scale) metal-organic frameworks (NMOFs), also known as coordination polymer particles (CPPs), have received much attention because of their structural diversities and tunable properties. Besides the direct use, NMOFs can be alternatively used as sacrificial templates/precursors for the preparation of a wide range of hybrid inorganic nanomaterials in straightforward and controllable manners. Distinct advantages of using NMOF templates are correlated to their structural and functional tailorability at molecular levels that is rarely acquired in any other conventional template/precursor. In addition, NMOF-derived inorganic nanomaterials with distinct chemical and physical properties are inferred to dramatically expand the scope of their utilization in many fields. In this review, we aim to provide readers with a comprehensive summary of recent progress in terms of synthetic approaches for the production of diverse inorganic hybrid nanostructures from as-synthesized NMOFs and their promising applications.