A Self-Templated Design Approach toward Multivariate Metal-Organic Frameworks for Enhanced Oxygen Evolution

Kg-Scale Synthesis of Ultrathin Single-Crystalline MOF/GO/MOF Sandwich Nanosheets with Elevated Electrochemical Performance

The scalable preparation of 2D ultrathin metal-organic framework (MOF) nanosheets remains a significant challenge due to low stripping efficiency and susceptibility to agglomeration. Herein, a facile strategy is developed for the synthesis of 2D ultrathin single-crystal MOF/graphene oxide (GO)/MOF (MGM) sandwich-like nanosheets based on the Ni/Co-BDC MOF (BDC = 1,4-terephthalic acid), with GO serving as a structure-directing agent. Impressively, 1 kg of MGM nanosheets can be obtained in a single batch with a metal-based yield of 98.73%. Furthermore, the universality of this strategy is implemented by the successful synthesis of three additional 2D ultrathin nanosheets: MGM7-ABDC, MGM7-FBDC, and MGM7-BPDC (metal = Ni, Co; ligands = 2-aminoterephthalic acid (2-ABDC), 2-fluoroterephthalic acid (2-FBDC), and 4,4'- biphenyl dicarboxylic acid (BPDC)). The as-prepared MGM7 nanosheets (Ni: Co ratio = 7:3) exhibit excellent electrochemical performance as the cathode for aqueous basic zinc battery (159.2 mA h g-1 at 1 A g-1), anode for sodium-ion battery (SIB, 593.0 mA h g-1 at 0.2 A g-1), and electrocatalyst for the oxygen evolution reaction (OER, 224 mV overpotential at 10 mA cm-2), significantly outperforming both bulk MOFs and conventional MOF nanosheets. This work enables the scalable synthesis of 2D MOF nanosheets with enhanced properties for multiple applications.

Recent Progress of Modulating Pristine Metal-Organic Frameworks for Oxygen Reaction Revolution

Highly efficient and stable oxygen evolution reaction (OER) electrocatalysts are essential for electrochemical water splitting. Among non-noble metal-based catalysts, metal-organic frameworks (MOFs) have recently emerged as particularly promising candidates due to their exceptional surface areas, hierarchical porous structures, and tunable morphologies and compositions. The rational regulation of the morphology and electronic structure of pristine MOFs is considered a critical pathway for enhancing active sites and structural stability, thereby significantly boosting the OER catalytic performance. This review systematically presents the recent advancements in modulating pristine MOFs via heterogeneous metal doping, ligand substitution, and hybrid composite construction. With particular emphasis on synthetic methods, modification mechanisms, and the OER properties of MOFs, we analyze the fundamental relationships between structural modifications and electrocatalytic performance. Through the systematic analysis of existing research achievements, this review provides a holistic assessment of current state-of-the-art developments, identifies critical challenges, and proposes future research directions with practical implications for OER electrocatalyst design.

Ferrocene-MOFs: Optimizing OER Kinetics for Water Splitting

Optimizing the adsorption and desorption kinetics of oxygen evolution reaction (OER) is crucial for efficient overall water splitting. Herein, we report a series of porous ferrocene-based metal-organic framework (MFc-MOF, M = Co, Ni, Fe, Mn) nanoflowers featuring a close π-π stacking lattice structure as model catalysts, and explore the structure-activity relationship. Operando electrochemical impedance spectroscopy implies that the synthesized CoFc-MOF@NF facilitates intermediate adsorption and desorption. It exhibits an ultralow overpotential of 189 mV at 10 mA cm-2 and maintains stability for 250 h. In an overall water splitting device, when CoFc-MOF@NF serves as the anode, it yields a significantly lower cell voltage than commercial RuO2 and shows excellent stability at 100 mA cm-2 for 100 h. In situ Raman spectroscopy reveals that the CoFc-MOF@NF surface transforms into CoFeOOH, the OER-active species, while preserving the MOF framework. The inner MOF's ferrocene units act as efficient electron-transfer mediators. These findings highlight CoFc-MOF@NF's potential as a leading catalyst for sustainable water splitting hydrogen production, combining high catalytic activity, rapid kinetics, and robust stability. This work presents a new approach to balance activity and stability in MOF-based OER catalysts.

Interface Engineering for Improved Large-Current Oxygen Evolution via Partial Phosphorization of Ce-MOF/NiCo-MOF Heterostructure

Interface engineering for electrocatalysts has proven to be an effective method for modulating electrocatalytic properties, yet a more efficient and straightforward strategy to construct a valid heterointerface for further enhancing interface effects is urgently needed for boosting oxygen evolution reactions (OER) at large current. Herein, a closely compacted heterostructure combining NiCo-metal-organic framework (MOF) and Ce-MOF is in situ formed through a one-step hydrothermal treatment, and partial phosphorization is employed to further enhance the interface effect between the newly formed urchin-shaped NiCoP shells and hexagonal rod-like Ce-MOF cores on nickel foam (NiCoP/Ce-MOF@NF). Experimental and theoretical results indicate that the heterogeneous NiCoP/Ce-MOF@NF, characterized by a more intensive interface rather than a simple physical mixture, generates an OER-beneficial electronic structure, significantly facilitates charge transfer and reaction kinetics, and creates a synergistically stable structure. The optimal NiCoP/Ce-MOF@NF exhibits remarkable electrocatalytic activity for OER, achieving an ultralow overpotential of 268 mV at a current density of 500 mA cm-2, and also delivers satisfactory large-current stability of up to 120 h. This work offers a novel approach for designing heterogeneous catalysts with strong interface effects for potential applications in industrial water electrolysis.

Two-dimensional nanomaterials based on rare earth elements for biomedical applications

As a kind of star materials, two-dimensional (2D) nanomaterials have attracted tremendous attention for their unique structures, excellent performance and wide applications. In recent years, layered rare earth-based or doped nanomaterials have become a new important member of the 2D nanomaterial family and have attracted significant interest, especially layered rare earth hydroxides (LREHs) and layered rare earth-doped perovskites with anion-exchangeability and exfoliative properties. In this review, we systematically summarize the synthesis, exfoliation, fabrication and biomedical applications of 2D rare earth nanomaterials. Upon exfoliation, the LREHs and layered rare earth-doped perovskites can be dimensionally reduced to ultrathin nanosheets which feature high anisotropy and flexibility. Subsequent fabrication, especially superlattice assembly, enables rare earth nanomaterials with diverse compositions and structures, which further optimizes or even creates new properties and thus expands the application fields. The latest progress in biomedical applications of the 2D rare earth-based or doped nanomaterials and composites is also reviewed in detail, especially drug delivery and magnetic resonance imaging (MRI). Moreover, at the end of this review, we provide an outlook on the opportunities and challenges of the 2D rare earth-based or doped nanomaterials. We believe this review will promote increasing interest in 2D rare earth materials and provide more insight into the artificial design of other nanomaterials based on rare earth elements for functional applications.

Room-Temperature Synthesized Iron/Cobalt Metal-Organic Framework Nanosheets with Highly Efficient Catalytic Activity toward Luminol Chemiluminescence Reaction

Two-dimensional (2D) iron/cobalt metal-organic framework nanosheets (Fe/Co-MOF NSs) were synthesized via the cooperative self-assembly reaction of Fe3+/Co2+ and terephthalic acid at room temperature. The as-prepared 2D Fe/Co-MOF NSs display superior performance in catalysis of the chemiluminescence (CL) reaction between luminol and H2O2. The CL spectrum, UV-vis absorption spectroscopy, radical scavenger experiments, and electron spin resonance (ESR) spectroscopy are utilized to research the possible CL mechanism of the luminol-H2O2-Fe/Co-MOF NSs system. All results indicate that Fe/Co-MOF NSs present outstanding peroxidase-like activity and could catalyze H2O2 to produce 1O2, O2·-, and ·OH, which could react rapidly with the luminol anion radical and result in strong CL. With the highly efficient CL of the luminol-H2O2-Fe/Co-MOF NSs system, a sensitive sensor for the detection of dopamine (DA) is developed based on the inhibitory effect of DA on the CL intensity. Good linearity over the range of 50-800 nM is achieved with a limit of detection of 20.88 nM (S/N = 3). This research demonstrates that 2D Fe/Co-MOF NSs is a highly effective catalyst for luminol CL reaction and has great application potential in the CL field.

Ultrafast and Scalable Fabrication of Coordination Polymer Films on Network Substrates via Thermal Current-Induced Dewetting

Coordination polymers are among the most favored active materials by researchers due to their broad application prospects. However, most of them are usually difficult to directly process into applicable devices because of their unsatisfied processability. One process of great concern for researchers is the in situ preparation of the coordination polymer on the applicable substrate, especially for the favored network substrates with good mechanical properties and 3D porous structure, which could provide obvious convenience and facilitation in the application process. Herein, we present an ultrafast and scalable thermal current-induced dewetting strategy to obtain uniform coordination polymer film in situ on network substrates, which could enable unprecedented convenience to obtain directly usable coordination polymer composites such as practical catalytic electrodes with excellent electrocatalytic performance. The proposed thermal current-induced dewetting method provides a highly adaptable and efficient practical production approach to integrate coordination polymer materials with network substrates and also provides new inspiration for understanding and applying the dewetting process on complex 3D network substrates.

(FeMnCe)-co-doped MOF-74 with significantly improved performance for overall water splitting

Developing inexpensive electrocatalysts with high activity and stability is of great value for overall water splitting. In this work, we designed a series of 3d-4f (FeMnCe)-trimetallic MOF-74 with different ratios of 3d- and 4f-metal centers. Among them, FeMn6Ce0.5-MOF-74/NF exhibited the best electrocatalytic performance for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline solution. It only requires a low overpotential of 281 mV@100 mA cm-2 for OER and 186 mV@-10 mA cm-2 for HER in 1 M KOH. With FeMn6Ce0.5-MOF-74/NF as the anode and cathode in the overall water splitting system, only 1.65 V is needed to deliver a current density of 10 mA cm-2. In particular, for the as-fabricated FeMn6Ce0.5-MOF-74/NF||Pt/C cell unit, only 1.40 V is needed to achieve 10 mA cm-2. Therefore, the successful design of 3d-4f mixed-metallic MOF-74 provides a new viewpoint to develop highly efficient non-precious metal electrocatalysts.