Electrostatically cooperative host-in-host of metal cluster ⊂ ionic organic cages in nanopores for enhanced catalysis

Construction of molecular compartments on the HKUST-1 for space-limited enhancement of visible light CO2 reduction

The construction of host structures with well-defined compartments that dispersedly accommodate catalytically active substances is a promising approach to significantly improve catalytic activity. Herein, we created separated compartments on the copper-based metal-organic framework (HKUST-1) by a mixed solvent-assisted approach and dispersedly confined tungstophosphoric acid hydrate (H3PW12O40) in its inner cavity structure to form the photocatalyst H3PW12O40@HKUST-1 with a novel "molecular compartment" structure. This structure not only enables the photosensitizer to be enriched in the interior of the "molecular compartment" structure to accelerate the photogenerated charge transfer but also creates a synergistic interaction between the H3PW12O40 units and the catalytic metal clusters in the main structure of the HKUST-1 to facilitate the photocatalytic CO2 reduction. H3PW12O40@HKUST-1 exhibits high CO2 to CO (415 μmol·g-1·h-1) and CH4 (37 μmol·g-1·h-1) conversion, corresponding to 73.9 % and 26.1 % selectivities for CO and CH4. This work provides a novel approach for the rational design of efficient catalysts for CO2 reduction.

Conversion of CO2 into cyclic carbonates using an ionic porous organic cage

The conversion of carbon dioxide (CO2) into value-added chemicals offers a promising path for greenhouse gas utilization. Porous organic cages (POCs), an emerging subclass of porous materials, have shown great potential in catalysis, primarily as catalyst supports and stabilizers for metal nanoparticles (MNPs) to enhance their catalytic activity. Herein, we report the use of an ionic POC (OFT-RCC36+6Br-) as a metal-free catalyst for the cycloaddition of CO2 and epoxides, generating cyclic carbonates in high yields. This POC catalyst is highly efficient, achieving a maximum yield of up to 90% with a turnover number (TON) of 3000 without requiring reaction solvents. Moreover, with the synergistic effect of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), the catalytic performance can be further enhanced across a wide substrate range.

Supercritical CO2-assisted synthesis of high-density Co clusters/N-doped porous carbon as bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) hold great promise for next-generation energy storage, but their practical application depends on the development of efficient bifunctional catalysts capable of catalyzing both the oxygen reduction reaction (ORR) during discharge and the oxygen evolution reaction (OER) during recharge. Herein, we propose a high-performance bifunctional oxygen electrocatalyst for ZABs, fabricated by encapsulating Co clusters into zeolite imidazole framework-8 (ZIF-8)-derived carbon via a supercritical CO2 (scCO2) fluid-assisted method. The dual-protection combining spatial confinement from porous carbon frameworks and strong Co-N coordination anchoring enables the stabilization of high-density Co clusters and preventing its aggregation. Furthermore, the scCO2 treatment reconstructs the mesoporous structure, significantly improving mass transport and exposing more accessible active sites. Density functional theory (DFT) calculations demonstrate that the surface Co-N moieties serve as highly active centers for the ORR, whereas the metallic Co sites within the clusters predominantly drive the OER. As a result, Co@N-C exhibits a remarkably low potential gap (ΔE = 0.68 V) between ORR and OER. When applied in aqueous ZABs, the catalyst delivers an impressive specific capacity of 780 mAh gZn-1 and a peak power density of 170 mW cm-2, surpassing Pt/C + RuO2. Moreover, the solid-state ZABs assembled with this catalyst achieve a high peak power density of 87.0 mW cm-2 along with long-time cycling stability of 200 h, demonstrating great potential for flexible and portable energy storage devices.

Ferritin-Inspired Encapsulation and Stabilization of Gold Nanoclusters for High-Performance Photothermal Conversion

Gold nanoclusters (AuNCs) are highly promising for applications in photothermal conversion due to their exceptional surface area and optical properties. However, their high surface energy often leads to aggregation, compromising stability and performance. To address this, we developed a ferritin-inspired covalent organic cage with a near-enclosed cavity to physically stabilize AuNCs. This superphane cage coordinates with Au3⁺ ions, forming highly stable and uniform AuNCs upon reduction. The encapsulated AuNCs exhibit broad absorption (250-2500 nm) and achieve remarkable photothermal conversion efficiency of 92.8% under 808 nm laser irradiation. At low power densities (0.5 W/cm2), temperatures reach 150 °C, and under one-sun illumination (1 kW/m2), the solar-to-vapor generation efficiency reaches 95.1%, with a water evaporation rate of 2.35 kg m-2 h-1. Even after 20 seawater desalination cycles, the system maintains a stable evaporation rate of 2.24 kg m-2 h-1, demonstrating excellent salt tolerance and durability. This ferritin-inspired strategy offers a robust platform for enhancing the stability and performance of AuNCs, advancing sustainable energy and water purification technologies.

Organic Cage Encapsulated Within Metal Cluster-Based Open Frameworks: A Single-Crystal Host-in-Host Material with Inter-Host Charge Cooperation

Integrating dissimilar building units of discrete organic cages and inorganic clusters into single-crystal supramolecular frameworks with tailored architectures and synergistic functions presents a significant challenge. Here, we presented our discovery of achieving such hybrids through electrostatically driven self-assembly of cationic ammonium organic cages with anionic lead iodide clusters. Notably, by carefully modulating the size, shape, and composition of cationic organic cages, we have constructed an integrated porous host-in-host architecture. In this system, the internal cationic cage snugly resided, encapsulated within the external network constructed from anionic lead iodide clusters. This unique nested hierarchy showcased enhanced interhost interactions facilitated by electrostatic forces, which intricately tailored the electronic structure of the outer lead iodide moiety. As a result, the hybrid demonstrated distinguished photophysical properties, including efficient oxygen activation and enhanced photothermal conversion capability, as confirmed by comprehensive experimental and theoretical analyses. The critical role of interhost electrostatic interactions was further demonstrated through a systematic comparison with a structurally similar host-in-host architecture comprising lead iodide clusters and neutral amine cages. Furthermore, the integrated and compartmentalized dual-host served as spatially isolated dual active sites for cascade reactions, exhibiting 33-47-folds enhancement in activity compared to structural counterparts lacking charge cooperation.

Bioinspired O2-Evolution Catalysts with Proton-Coupled Electron Transfer Pathway for Portable Oxygen Generation

Producing high-purity oxygen (O2) has a wide range of applications across diverse sectors, such as medicine, tunnel construction, the chemical industry, and fermentation. However, current O2 production methods are burdened by complexity, heavy equipment, high energy consumption, and limited adaptability to harsh environments. Here, to address this grand challenge, the de novo design of Ru-doped metal hydroxide is proposed to serve as bioinspired O2-evolution catalysts with proton-coupled electron transfer (PCET) pathway for low-energy, environmentally friendly, cost-effective, and portable O2 generation. The comprehensive studies confirm that the lattice H species in Ru-Co(OH)x-based O2-evolution catalyst can trigger a PCET pathway to optimize Ru-oxygen intermediates interactions, thus ultimately reducing reaction energy barriers and improving the activities and durabilities. Consequently, the prepared Ru-Co(OH)x-loaded membrane catalysts exhibit rapid and long-term stable O2 production capabilities. Furthermore, the proposed material design strategy of lattice H-species shows remarkable universality and adaptability to broad Ru-doped metal hydroxides. This efficient, portable, and cost-effective O2 generation technique is suggested to ensure an uninterrupted O2 supply during emergencies and in regions with limited O2 availability or air pollution, thus offering significant societal benefits in broad applications.

Facilitating alkaline hydrogen evolution kinetics via interfacial modulation of hydrogen-bond networks by porous amine cages

The electrode-electrolyte interface is pivotal in the electrochemical kinetics. However, modulating the electrochemical interface at the atomic or molecular level is challenging due to the lack of efficient interfacial regulators. Here, we employ a porous amine cage as an interfacial modifier to Pt cluster in a confining configuration, largely enhancing alkaline HER kinetics by facilitating charge transfer. In situ electrochemical surface-enhanced Raman spectra, in combination with the ab initio molecular dynamics simulation, elucidates that the interaction between water and the -NH- moiety of cage frame softens the H-bonds net of interfacial water, making it more flexible for charge transfer. Moreover, our investigation pinpointed that the -NH- moiety acted as a pump for charge transfer by Grotthuss mechanism, lowering the kinetic barrier for hydrogen adsorption. Our findings highlight the strategy of establishing a soft-confining interfacial modifier by porous cage, offering opportunities to optimize electrochemical interfaces and promote reaction kinetics in a targeted way.

Porous Supramolecular Assemblies for Efficient Suzuki Coupling of Aryl Chlorides

The development of catalytic systems that can activate aryl chlorides for palladium-catalyzed cross-coupling reactions is at the forefront of ongoing efforts to synthesize fine chemicals. In this study, a facile ligand-template approach is adopted to achieve active-site encapsulation by forming supramolecular assemblies; this bestowed the pristine inert counterparts with reactivity, which is further increased upon the construction of a porous framework. Experimental results indicated that the isolation of ligands by the surrounding template units is key to the formation of catalytically active monoligated palladium complexes. Additionally, the construction of porous frameworks using the resulting supramolecular assemblies prevented the decomposition of the Pd complexes into nanoparticles, which drastically increased the catalyst lifetime. These findings, along with the simplicity and generality of the synthesis scheme, suggest that the strategy can be leveraged to achieve unique reactivity and potentially enable fine-chemical synthesis.

Recent Advances in Confining Polyoxometalates and the Applications

Polyoxometalates (POMs) are widely used in catalysis, energy storage, biomedicine, and other research fields due to their unique acidity, photothermal, and redox features. However, the leaching and agglomeration problems of POMs greatly limit their practical applications. Confining POMs in a host material is an efficient tool to address the above-mentioned issues. POM@host materials have received extensive attention in recent years. They not only inherent characteristics of POMs and host, but also play a significant synergistic effect from each component. This review focuses on the recent advances in the development and applications of POM@host materials. Different types of host materials are elaborated in detail, including tubular, layered, and porous materials. Variations in the structures and properties of POMs and hosts before and after confinement are highlighted as well. In addition, an overview of applications for the representative POM@host materials in electrochemical, catalytic, and biological fields is provided. Finally, the challenges and future perspectives of POM@host composites are discussed.

Immobilizing Metal Nanoparticles on Hierarchically Porous Organic Cages with Size Control for Enhanced Catalysis

Incorporating metal nanoparticles (MNPs) into porous composites with controlled size and spatial distributions is beneficial for a broad range of applications, but it remains a synthetic challenge. Here, we present a method to immobilize a series of highly dispersed MNPs (Pd, Ir, Pt, Rh, and Ru) with controlled size (<2 nm) on hierarchically micro- and mesoporous organic cage supports. Specifically, the metal-ionic surfactant complexes serve as both metal precursors and mesopore-forming agents during self-assembly with a microporous imine cage CC3, resulting in a uniform distribution of metal precursors across the resultant supports. The functional heads on the ionic surfactants as binding sites, together with the nanoconfinement of pores, guide the nucleation and growth of MNPs and prevent their agglomeration after chemical reduction. Moreover, the as-synthesized Pd NPs exhibit remarkable activity and selectivity in the tandem reaction due to the advantages of ultrasmall particle size and improved mass diffusion facilitated by the hierarchical pores.

Cooperative cage hybrids enabled by electrostatic marriage

A cage hybrid (C-Cage-PB) was developed by electrostatic complexation of a quaternary ammonium cage (C-Cage⁺) and an anionic inorganic Prussian blue (PB^-). Given the unique synergy of the two parts, such a cage hybrid can be used as a promising platform for the efficient removal of toxic compounds in wastewater through adsorption, delivery or catalytic degradation via a Fenton oxidation reaction. In addition, C-Cage-PB can encapsulate Pd clusters, which amplifies the function of the hybrid for enhanced catalytic performance in the sequential degradation of toxic organic compounds and heavy metal pollution in wastewater treatment.

Air-Stable Radical Organic Cages as Cascade Nanozymes for Enhanced Catalysis

The pursuit of single-assembled molecular cage reactors for complex tandem reactions is a long-standing target in biomimetic catalysis but still a grand challenge. Herein, nanozyme-like organic cages are reported by engineering air-stable radicals into the skeleton upon photoinduced electron transfer. The generation of radicals is accompanied by single-crystal structural transformation and exhibits superior stability over six months in air. Impressively, the radicals throughout the cage skeleton can mimic the peroxidase of natural enzymes to decompose H₂ O₂ into OH· and facilitate oxidation reactions. Furthermore, an integrated catalyst by encapsulating Au clusters (glucose oxidase mimics) into the cage has been developed, in which the dual active sites (Au cluster and radical) are spatially isolated and can work as cascade nanozymes to prominently promote the enzyme-like tandem reaction via a substrate channeling effect.

Progress and Perspectives of Single-Atom Catalysts for Gas Sensing

Single-atom catalysts (SACs) attract extensive attention in the field of heterogeneous catalysis in recent years due to the maximum atom utilization and unique physical and chemical properties. The gas sensing is actually a heterogeneous catalysis process but the SACs are new to this area. Although SACs show huge potential in gas sensing, the SACs gas sensing area currently is still at the infancy stage. This work critically reviews the recent advances and current status of single-atom gas sensing materials. General synthesis routes, characterization methods, and sensing performance indexes are introduced. At the end, the challenges and future prospects on SACs gas sensing are presented from the authors' perspectives. This work is anticipated to provide insights and guideline for the chemical sensing community.