Rim-Based Binding of Perfluorinated Acids to Pillararenes Purifies Water.

Per- and polyfluoroalkyl substances (PFAS) pose a rapidly increasing global problem as their widespread use and high stability lead worldwide to water contamination, with significant detrimental health effects.[1] Supramolecular chemistry has been invoked to develop materials geared towards the specific capture of PFAS from water,[2] to reduce the concentration below advisory safety limits (e.g., 70 ng/L for the sum of perfluorooctane sulfonic acid, PFOS and perfluorooctanoic acid, PFOA). Scale-up and use in natural waters with high PFAS concentrations has hitherto posed a problem. Here we report a new type of host-guest interaction between deca-ammonium-functionalized pillar[5]arenes (DAF-P5s) and perfluoroalkyl acids. DAF-P5 complexes show an unprecedented 1 : 10 stoichiometry, as confirmed by isothermal calorimetry and X-ray crystallographic studies, and high binding constants (up to 106 M-1) to various polyfluoroalkyl acids. In addition, non-fluorinated acids do not hamper this process significantly. Immobilization of DAF-P5s allows a simple single-time filtration of PFAS-contaminated water to reduce the PFOS/PFOA concentration 106 times to 15-50 ng/L level. The effective and fast (<5 min) orthogonal binding to organic molecules without involvement of fluorinated supramolecular hosts, high breakthrough capacity (90 mg/g), and robust performance (>10 regeneration cycles without decrease in performance) set a new benchmark in PFAS-absorbing materials.

A Solvent-Polarity-Induced Interface Self-Assembly Strategy towards Mesoporous Triazine-Based Carbon Materials.

Triazine-based materials with porous structure have recently received numerous attentions as a fascinating new class because of their superior potential for various applications. However, it is still a formidable challenge to obtain triazine-based materials with precise adjustable meso-scaled pore sizes and controllable pore structures by reported synthesis approaches. Herein, we develop a solvent polarity induced interface self-assembly strategy to construct mesoporous triazine-based carbon materials. In this method, we employ a mixed solvent system within a suitable range of polarity (0.223≤Lippert-Mataga parameter (Δf) ≤0.295) to induce valid self-assembly of skeleton precursor and surfactant. The as-prepared mesoporous triazine-based carbon materials possess uniform tunable pore sizes (8.2-14.0 nm), high surface areas and ultrahigh nitrogen content (up to 18 %). Owing to these intriguing advantages, the fabricated mesoporous triazine-based carbon materials as functionalized porous solid absorbents exhibit predominant CO2 adsorption performance and exceptional selectivity for the capture of CO2 over N2 .

Ligand-Assisted Coordinative Self-Assembly Method to Synthesize Mesoporous ZnxCd1-xS Nanospheres with Nano-Twin-Induced Phase Junction for Enhanced Photocatalytic H2 Evolution.

The designed synthesis of nanotwin architectures and thus-induced phase junctions expresses huge significance for semiconductor photocatalysts. However, current methods of producing nanotwins mainly involve high-temperature thermal treatment and tedious reaction steps, generally resulting in large bulk structure with ill-defined morphology and low specific surface area. Here, we propose a mild ligand-assisted coordinative self-assembly method to synthesize uniform mesoporous ZnxCd1-xS nanospheres with ultrahigh surface areas (148-312 m2 g-1) and controllable diameter (90-370 nm). Moreover, the sample possesses abundant phase junctions induced by nanotwins containing both hexagonal and cubic segments. With the synergy of the twin-induced phase junctions and high surface area, the as-prepared mesoporous Zn0.82Cd0.18S nanospheres exhibit a remarkable photocatalytic H2 evolution rate of 13.46 mmol h-1 g-1 with free noble metal. The mechanism of photocarrier dynamics was studied by transient photovoltage spectroscopy, manifesting that the photocarrier lifetime of Zn0.82Cd0.18S is largely prolonged and therefore improves the charge separation efficiency and photocatalytic activity.

Mesoporous Metal Oxide Encapsulated Gold Nanocatalysts: Enhanced Activity for Catalyst Application to Solvent-Free Aerobic Oxidation of Hydrocarbons.

Here, we present a series of experimental studies to encapsulate ultrasmall gold nanoparticles into mesoporous metal oxide via an in situ self-assembly method. Notably, the 2.0Au@mZnO catalyst (∼2.0 nm gold nanoparticles loading on mesoporous ZnO nanospheres) shows excellent catalytic activity for indane oxidation (120 °C, conversion 88.5%) and affords much high turnover frequencies (9521 h-1). The catalytic activity of these gold-based catalysts was found to be correlated with the size of gold nanoparticles and the types of metal oxide supports. With a decrease in gold nanoparticle size, the catalytic conversion efficiency of indane oxidation increased. In addition, such catalysts possessed high thermal and chemical stability and could be reused more than 10 times without a remarkable loss of catalytic activity.

Rim-differentiated pillar[5]arene-modified surfaces for rapid PFOA/PFOS detection.

A new rim-differentiated pillar[5]arene (RD-P5) has been synthesized and immobilized onto an Al2O3 surface for the rapid detection of perfluoroalkyl acids. This P5-Al2O3 surface provides a novel approach for measuring perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) using contact angle measurements, with limits of detection down to 10 ng L-1.

2D and 3D Self-Assembly of Fluorine-Free Pillar-[5]-Arenes and Perfluorinated Diacids at All-Aqueous Interfaces.

The interaction of perfluorinated molecules, also known as "forever chemicals" due to their pervasiveness, with their environment remains an important yet poorly understood topic. In this work, the self-assembly of perfluorinated molecules with multivalent hosts, pillar-[5]-arenes, is investigated. It is found that perfluoroalkyl diacids and pillar-[5]-arenes rapidly and strongly complex with each other at aqueous interfaces, forming solid interfacially templated films. Their complexation is shown to be driven primarily by fluorophilic aggregation and assisted by electrostatic interactions, as supported by the crystal structure of the complexes, and leads to the formation of quasi-2D phase-separated films. This self-assembly process can be further manipulated using aqueous two-phase system microdroplets, enabling the controlled formation of 3D micro-scaffolds.

Solvent-Induced Self-Assembly Strategy to Synthesize Well-Defined Hierarchically Porous Polymers.

Porous polymers with well-orchestrated nanomorphologies are useful in many fields, but high surface area, hierarchical structure, and ordered pores are difficult to be satisfied in one polymer simultaneously. Herein, a solvent-induced self-assembly strategy to synthesize hierarchical porous polymers with tunable morphology, mesoporous structure, and microporous pore wall is reported. The poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer micelles are cross-linked via Friedel-Crafts reaction, which is a new way to anchor micelles into porous polymers with well-defined structure. Varying the polarity of the solvent has a dramatic effect upon the oleophobic/oleophylic interaction, and the self-assembly structure of PEO-b-PS can be tailored from aggregated nanoparticles to hollow spheres even mesoporous bulk. A morphological phase diagram is accomplished to systematically evaluate the influence of the composition of PEO-b-PS and the mixed solvent component on the pore structure and morphology of products. The hypercrosslinked hollow polymer spheres provide a confined microenvironment for the in situ reduction of K2 PdCl4 to ultrasmall Pd nanoparticles, which exhibit excellent catalytic performance in solvent-free catalytic oxidation of hydrocarbons and alcohols.

Boosting High-Rate Zinc-Storage Performance by the Rational Design of Mn2O3 Nanoporous Architecture Cathode.

Manganese oxides are regarded as one of the most promising cathode materials in rechargeable aqueous Zn-ion batteries (ZIBs) because of the low price and high security. However, the practical application of Mn2O3 in ZIBs is still plagued by the low specific capacity and poor rate capability. Herein, highly crystalline Mn2O3 materials with interconnected mesostructures and controllable pore sizes are obtained via a ligand-assisted self-assembly process and used as high-performance electrode materials for reversible aqueous ZIBs. The coordination degree between Mn2+ and citric acid ligand plays a crucial role in the formation of the mesostructure, and the pore sizes can be easily tuned from 3.2 to 7.3 nm. Ascribed to the unique feature of nanoporous architectures, excellent zinc-storage performance can be achieved in ZIBs during charge/discharge processes. The Mn2O3 electrode exhibits high reversible capacity (233 mAh g-1 at 0.3 A g-1), superior rate capability (162 mAh g-1 retains at 3.08 A g-1) and remarkable cycling durability over 3000 cycles at a high current rate of 3.08 A g-1. Moreover, the corresponding electrode reaction mechanism is studied in depth according to a series of analytical methods. These results suggest that rational design of the nanoporous architecture for electrode materials can effectively improve the battery performance.