Synergistic Effect Improves the Response of Active Sites to Target Variations for Picomolar Detection of Silver Ions.

Heavy metal ions seriously threaten human health; even a trace of them can damage the renal, nervous, and immune systems irreversibly. Although established nanozyme-based colorimetric assays have been designed for the rapid detection of heavy metal ions, the general contained surface organic ligands of nanocatalysts and low absorptivity of metal ions on solid substrates might result in a weak effect on active sites and prevent the realization of their full detection potential. Here, we developed a nanozyme-based colorimetric sensor (CPM-Pt) made by pyrolysis of peat moss with preabsorbed traces of Pt ions to ultrasensitively detect Ag+. The calcination removes organic components and produces bare nanozymes that expose rich active sites. The strong protective effect from the porous carbon support enables the embedded Pt nanoparticles (Pt NPs) with a partially stable positive charge after pyrolysis (∼28% Pt2+ species). By the d8-d10 metal-metal interactions between Pt2+ (4f145d8) and Ag+ (4d10), the high proportion of Pt2+ species on the surface of Pt NPs can readily capture/absorb Ag+. Subsequently, Ag+ accepts electrons from the support to form Ag atoms, which rapidly cover the peroxidase-like active sites of bare Pt NPs, weakening the activation of H2O2 to realize the response of Ag+. The colorimetric detection limit of Ag+ reached an unprecedented 1.1 pM, and the corresponding naked-eye color recognition is ultrasensitive to extremely low levels (100 pM).

Electronic Metal-Support Interaction Directing the Design of Fe(III)-Based Catalysts for Efficient Advanced Oxidation Processes by Dual Reaction Paths.

Persistent organic pollutants (POPs) have a huge impact on human health due to their high toxicity and non-degradability. It is still of great difficulty to develop highly efficient catalysts toward the degradation of POPs. Herein, it is reported that regulating electronic structure of quasi-single atomic ferric iron (Fe(III)) in the VO2 support through the electronic metal-support interaction (EMSI) is a versatile strategy to enhance the catalytic activity. Activated Fe(III) can react with peroxydisulfate (PDS) to produce both radicals and high-valent iron (HVFe) simultaneously for the efficient and fast degradation of POPs. Density functional theory (DFT) calculations prove that the influence of EMSI promotes the electrons on Fe(III) 3d-bond center moving close to the Fermi level, facilitating the charge transfer from Fe(III) to the adsorbate. Through the control experiments, both the radical path by PDS and the HVFe path aroused by the EMSI are confirmed in the POP degradation process. Consequently, the Fe/VO2 catalyst exhibits record-breaking catalytic activity with the k-value as high as 56.7, 43.3 µmol s-1 g-1 for p-chlorophenol and 2,4-dichlorophenol degradation, respectively.

Progress in Hybridization of Covalent Organic Frameworks and Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) hybrid materials are a class of porous crystalline materials that integrate MOFs and COFs with hierarchical pore structures. As an emerging porous frame material platform, MOF/COF hybrid materials have attracted tremendous attention, and the field is advancing rapidly and extending into more diverse fields. Extensive studies have shown that a broad variety of MOF/COF hybrid materials with different structures and specific properties can be synthesized from diverse building blocks via different chemical reactions, driving the rapid growth of the field. The allowed complementary utilization of π-conjugated skeletons and nanopores for functional exploration has endowed these hybrid materials with great potential in challenging energy and environmental issues. It is necessary to prepare a "family tree" to accurately trace the developments in the study of MOF/COF hybrid materials. This review comprehensively summarizes the latest achievements and advancements in the design and synthesis of MOF/COF hybrid materials, including COFs covalently bonded to the surface functional groups of MOFs (MOF@COF), MOFs grown on the surface of COFs (COF@MOF), bridge reaction between COF and MOF (MOF+COF), and their various applications in catalysis, energy storage, pollutant adsorption, gas separation, chemical sensing, and biomedicine. It concludes with remarks concerning the trend from the structural design to functional exploration and potential applications of MOF/COF hybrid materials.

Signal Amplification Strategy Using Atomically Gold-Supported VO2 Nanobelts as a Co-reaction Accelerator for Ultrasensitive Electrochemiluminescent Sensor Construction Based on the Resonance Energy Transfer Platform.

Luminol, as a classical luminophore, plays a crucial role in electrochemiluminescence (ECL). However, the traditional luminol-H2O2 ECL system suffers from the self-decomposition of H2O2 at ambient temperature, which hinders its further application in quantitative analysis. In this work, for the first time, we developed atomically gold-supported two-dimensional VO2 nanobelts (Au/VO2) as an advanced co-reaction promoter to speed up the reduction of dissolved oxygen to superoxide radicals (O2•-), which react with the luminol anion radical and greatly promote the ECL emission. The ECL resonance energy transfer (ECL-RET) between the hollow manganese dioxide nanospheres and luminol results in a conspicuously decreased ECL signal response, and in the presence of glutathione (GSH), effective redox reaction between manganese dioxide and GSH restores the ECL signal. As a consequence, the designed sensor based on ECL-RET-assisted Au/VO2 signal amplification showed outstanding performance for "signal-on" detection of GSH in the concentration range of 10-3 to 10-10 M, and the detection limit was as low as 0.03 nM. The ECL sensor displayed excellent specificity and was successfully utilized to target GSH in real human serum samples. Importantly, this work not only highlights a powerful avenue for constructing an ultrasensitive ECL sensor for GSH but also provides some inspiration for the further design of high-performance co-reaction accelerators using the ECL technique.

Tailoring the Electronic Metal-Support Interactions in Supported Atomically Dispersed Gold Catalysts for Efficient Fenton-like Reaction.

The atomically dispersed metal is expected as one of the most promising Fenton-like catalysts for the degradation of recalcitrant organic pollutants (ROPs) by the strong "electronic metal-support interactions" (EMSIs). Here, we develop an atomically dispersed metal-atom alloy made by guest Au atoms substitute host V atoms in the two-dimensional VO2 (B) nanobelt support (Au/VO2 ) to activate Fenton-like oxidation for elimination of ROPs. The 2D nanobelt structure enlarges the exposure of atomically Au thus increasing the number of active sites to absorb more S2 O8 2- ions. And the EMSIs regulate the charge density in Au atoms to present positive charge Au+ , lowering the energy barrier of S2 O8 2- decomposition to produce SO4 .- . The Au/VO2 catalyst possesses excellent durable and reliable characteristics and exhibits record-breaking efficiency with TOF as high as 21.42 min-1 , 16.19 min-1 , and 80.89 min-1 for rhodamine, phenol, and bisphenol A degradation, respectively.

Iron regulates the interfacial charge distribution of transition metal phosphides for enhanced oxygen evolution reaction.

Using earth abundant elements to develop oxygen evolution reaction (OER) electrocatalysts presents one of the most promising strategies to generate clean and renewable energy systems to deal with the ever-growing energy crisis. The challenge comes as how to rationally design the chemical composition and nanostructure to increase the OER efficiency. In this work, we demonstrated an operational ion strategy to improve OER performances of iron cobalt bimetallic phosphide (Fe0.5Co-P), which was fabricated by simultaneous annealing and phosphating metal organic framework (MOF) precursors. The iron regulates the charge density of the Co sites, changing the electronic structure of the phase interface for endowing dramatically enhanced OER activity. The Fe0.5Co-P catalyst possesses excellent durable and reliable characteristics and exhibits dramatically enhanced OER efficiency with an overpotential of only 260 mV to drive a current density of 10 mA cm-2 and a Tafel slope of 65.53 mV dec-1 in 1.0 M KOH. The work provides useful insights into the design and synthesis of multicomponent metal phosphides-based OER catalysts for practical application in water splitting.

Confining Metal-Organic Framework in the Pore of Covalent Organic Framework: A Microscale Z-Scheme System for Boosting Photocatalytic Performance.

The search for building hierarchical porous materials with accelerated photo-induced electrons and charge-carrier separation is important because they hold great promise for applications in various fields. Here, a facile strategy of confining metal-organic framework (MOF) in the 1D channel of the 2D covalent organic framework (COF) to construct a novel COF@MOF micro/nanopore network is proposed. Specifically, a nitrogen-riched COF (TTA-BPDA-COF) is chosen as the platform for in-situ growth of a Co-based MOF (ZIF-L-Co) to form a TTA-BPDA-COF@ZIF-L-Co hybrid material. The hierarchical porous structure endows TTA-BPDA-COF@ZIF-L-Co with superior adsorption capacity. In addition, the integration of TTA-BPDA-COF and ZIF-L-Co forms a Z-scheme photocatalytic system, which significantly improved the redox properties and accelerated the separation of photogenerated charges and holes, achieving great improvement in photocatalytic activity. This confinement engineering strategy provides a new idea to construct a versatile molecular-material photocatalytic platform.