Anisotropic and Ultralow Phonon Thermal Transport in Organic–Inorganic Hybrid Perovskites: Atomistic Insights into Solar Cell Thermal Management and Thermoelectric Energy Conversion Efficiency

Energy‐related functionality and performance of organic–inorganic hybrid perovskites, such as methylammonium lead iodide (MAPbI₃), highly depend on their thermal transport behavior. Using equilibrium molecular dynamics simulations, it is discovered that the thermal conductivities of MAPbI₃ under different phases (cubic, tetragonal, and orthorhombic) are less than 1 W m^?1 K^?1, and as low as 0.31 W m^?1 K^?1 at room temperature. Such ultralow thermal conductivity can be attributed to the small phonon group velocities due to their low elastic stiffness, in addition to their short phonon lifetimes (<100 ps) and mean‐free‐paths (<10 nm) due to the enhanced phonon–phonon scattering from highly‐overlapped phonon branches. The anisotropy in thermal conductivity at lower temperatures is found to associate with preferential orientations of organic CH₃NH₃⁺ cations. Among all atomistic interactions, electrostatic interactions dominate thermal conductivities in ionic MAPbI₃ crystals. Furthermore, thermal conductivities of general hybrid perovskites MABX₃ (B = Pb, Sn; X = I, Br) have been qualitatively estimated and found that Sn‐ or Br‐based perovskites possess higher thermal conductivities than Pb‐ or I‐based ones due to their much higher elastic stiffness. This study inspires optimal selections and rational designs of ionic components for hybrid perovskites with desired thermal conductivity for thermally‐stable photovoltaic or highly‐efficient thermoelectric energy harvesting/conversion applications.     

High Thermoelectric Performance in PbTe Due to Large Nanoscale Ag2Te Precipitates and La Doping

Thermoelectrics are being rapidly developed for waste heat recovery applications, particularly in automobiles, to reduce carbon emissions. PbTe‐based materials with small (<20 nm) nanoscale features have been previously shown to have high thermoelectric figure‐of‐merit, zT, largely arising from low lattice thermal conductivity particularly at low temperatures. Separating the various phonon scattering mechanisms and the electronic contribution to the thermal conductivity is a serious challenge to understanding, and further optimizing, these nanocomposites. Here we show that relatively large nanometer‐scale (50–200 nm) Ag₂Te precipitates in PbTe can be controlled according to the equilibrium phase diagram and these materials show intrinsic semiconductor behavior with high electrical resistivity, enabling direct measurement of the phonon thermal conductivity. This study provides direct evidence that even large nanometer‐scale microstructures reduce thermal conductivity below that of a macro‐scale composite of saturated alloys with Kapitza‐type interfacial thermal resistance at the same overall composition. Carrier concentration control is achieved with lanthanum doping, enabling independent control of the electronic properties and microstructure. These materials exhibit lattice thermal conductivity which approaches the theoretical minimum above ～650 K, even lower than that found with small nanoparticles. Optimally La‐doped n‐type PbTe‐Ag₂Te nanocomposites exhibit zT > 1.5 at 775 K.     

From Bonding Asymmetry to Anharmonic Rattling in Cu12Sb4S13 Tetrahedrites: When Lone‐Pair Electrons Are Not So Lonely

Some of the best thermoelectrics are complex materials with rattling guests inside oversized atomic cages. Understanding the chemical and structural origins of the rattling behavior is essential to the design of thermoelectric materials. In this work, a clear connection is established between the local bonding asymmetry and anharmonic rattling modes in tetrahedrite thermoelectrics, enabled by the chemically active electron lone pairs. The studies reveal a five‐atom atomic cage Sb[CuS₃]Sb in Cu₁₂Sb₄S₁₃ tetrahedrites that exhibits strong local bonding asymmetry: covalent bonding inside the CuS₃ trigonal plane and weak out‐of‐plane bonding induced by the lone‐pair electrons of Sb. This bonding asymmetry leads to out‐of‐plane rattling modes that are quasilocalized and anharmonic with low frequency and large amplitude, and are likely the origin of low thermal conductivity in tetrahedrites. Such knowledge highlights the importance of local structure asymmetry and lone‐pair atoms in driving anharmonic rattling, providing a stepping stone to the discovery and design of next‐generation thermoelectrics.     

Microstructure‐Lattice Thermal Conductivity Correlation in Nanostructured PbTe0.7S0.3 Thermoelectric Materials

The reduction of thermal conductivity, and a comprehensive understanding of the microstructural constituents that cause this reduction, represent some of the important challenges for the further development of thermoelectric materials with improved figure of merit. Model PbTe‐based thermoelectric materials that exhibit very low lattice thermal conductivity have been chosen for this microstructure–thermal conductivity correlation study. The nominal PbTe_0.7S_0.3 composition spinodally decomposes into two phases: PbTe and PbS. Orderly misfit dislocations, incomplete relaxed strain, and structure‐modulated contrast rather than composition‐modulated contrast are observed at the boundaries between the two phases. Furthermore, the samples also contain regularly shaped nanometer‐scale precipitates. The theoretical calculations of the lattice thermal conductivity of the PbTe_0.7S_0.3 material, based on transmission electron microscopy observations, closely aligns with experimental measurements of the thermal conductivity of a very low value, ～0.8 W m^?1 K^?1 at room temperature, approximately 35% and 30% of the value of the lattice thermal conductivity of either PbTe and PbS, respectively. It is shown that phase boundaries, interfacial dislocations, and nanometer‐scale precipitates play an important role in enhancing phonon scattering and, therefore, in reducing the lattice thermal conductivity.     

Thermal Conductivity and Phonon Scattering Processes of ALD Grown PbTe–PbSe Thermoelectric Thin Films

This work studies the thermal conductivity and phonon scattering processes in a series of n‐type lead telluride‐lead selenide (PbTe–PbSe) nanostructured thin films grown by atomic layer deposition (ALD). The ALD growth of the PbTe–PbSe samples in this work results in nonepitaxial films grown directly on native oxide/Si substrates, where the Volmer–Weber mode of growth promotes grains with a preferred columnar orientation. The ALD growth of these lead‐rich PbTe, PbSe, and PbTe–PbSe thin films results in secondary oxide phases, along with an increase microstructural quality with increased film thickness. The compositional variation and resulting point and planar defects in the PbTe–PbSe nanostructures give rise to additional phonon scattering events that reduce the thermal conductivity below that of the corresponding ALD‐grown control PbTe and PbSe films. Temperature‐dependent thermal conductivity measurements show that the phonon scattering in these ALD‐grown PbTe–PbSe nanostructured materials, along with ALD‐grown PbTe and PbSe thin films, are driven by extrinsic defect scattering processes as opposed to phonon–phonon scattering processes intrinsic to the PbTe or PbSe phonon spectra. The implication of this work is that polycrystalline, nanostructured ALD composites of thermoelectric PbTe–PbSe films are effective in reducing the phonon thermal conductivity, and represent a pathway for further improvement of the figure of merit (ZT), enhancing their thermoelectric application potential.     

Light‐Induced Swelling‐Responsive Conductive,Adhesive, and Stretchable Wireless Film Hydrogel as Electronic Artificial Skin

Light‐induced wireless soft electronic skin hydrogels with excellent mechanical and electronic properties are important for several applications, such as soft robotics and intelligent wearable devices. Precise control of reversible stretchability and capacitive properties depending on intermolecular interaction and surface characteristics remains a challenge. Here, a thin‐film hydrogel is designed based on titanium oxide (TiO₂) polydopamine–perfluorosilica carbon dot‐conjugated chitosan–polyvinyl alcohol‐loaded tannic acid with controllable hydrophobic–hydrophilic transition in the presence of UV–vis light irradiation. The shifting of surface wettability from hydrophobic to hydrophilic by irradiation affects thin‐film water permeability and swelling ratio. This allows the penetration of water into the matrix to change its mechanical strength, electronic properties, and adhesive behavior. Specifically, the hydrogel displays mechanical strain as high as 278% in response to light stimuli and demonstrates the ability to regain its initial state determining the elasticity of the fabricated material. Moreover, the thin‐film hydrogel shows an increase in conductivity to 1.096 × 10^?3 and 1.026 × 10^?3 S cm^?1 when irradiated with UV and visible light, respectively. The hydrogel exhibits capacitive reversibility that follows finger motion which can be identified directly or remotely using wireless connection, indicative of its possible applications as an artificial electronic skin.     

In Situ Formation of Copper‐Based Hosts Embedded within 3D N‐Doped Hierarchically Porous Carbon Networks for Ultralong Cycle Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising energy storage systems due to their large theoretical energy density of 2600 Wh kg^?1 and cost effectiveness. However, the severe shuttle effect of soluble lithium polysulfide intermediates (LiPSs) and sluggish redox kinetics during the cycling process cause low sulfur utilization, rapid capacity fading, and a low coulombic efficiency. Here, a 3D copper, nitrogen co‐doped hierarchically porous graphitic carbon network developed through a freeze‐drying method (denoted as 3D Cu@NC‐F) is prepared, and it possesses strong chemical absorption and electrocatalytic conversion activity for LiPSs as highly efficient sulfur host materials in Li–S batteries. The porous carbon network consisting of 2D cross‐linked ultrathin carbon nanosheets provides void space to accommodate volumetric expansion upon lithiation, while the Cu, N‐doping effect plays a critical role for the confinement of polysulfides through chemical bonding. In addition, after sulfuration of Cu@NC‐F network, the in situ grown copper sulfide (Cu_xS) embedded within Cu_xS@NC/S‐F composite catalyzes LiPSs conversion during reversible cycling, resulting in low polarization and fast redox reaction kinetics. At a current density of 0.1 C, the Cu_xS@NC/S‐F composites' electrode exhibits an initial capacity of 1432 mAh g^?1 and maintains 1169 mAh g^?1 after 120 cycles, with a coulombic efficiency of nearly 100%.     

Gate‐Induced Massive and Reversible Phase Transition of VO2 Channels Using Solid‐State Proton Electrolytes

The use of gate bias to control electronic phases in VO₂, an archetypical correlated oxide, offers a powerful method to probe their underlying physics, as well as for the potential to develop novel electronic devices. Up to date, purely electrostatic gating in 3‐terminal devices with correlated channel shows the limited electrostatic gating efficiency due to insufficiently induced carrier density and short electrostatic screening length. Here massive and reversible conductance modulation is shown in a VO₂ channel by applying gate bias V_G at low voltage by a solid‐state proton (H⁺) conductor. By using porous silica to modulate H⁺ concentration in VO₂, gate‐induced reversible insulator‐to‐metal (I‐to‐M) phase transition at low voltage, and unprecedented two‐step insulator‐to‐metal‐to‐insulator (I‐to‐M‐to‐I) phase transition at high voltage are shown. V_G strongly and efficiently injects H⁺ into the VO₂ channel without creating oxygen deficiencies; this H⁺‐induced electronic phase transition occurs by giant modulation (≈7%) of out‐of‐plane lattice parameters as a result of H⁺‐induced chemical expansion. The results clarify the role of H⁺ on the electronic state of the correlated phases, and demonstrate the potentials for electronic devices that use ionic/electronic coupling.     

Obtaining Material Based on Copper Selenide by the Methods of Powder Metallurgy

Copper selenide is a promising material for power generation in a medium-temperature range 600–1000 K. A number of features of the Cu–Se system, namely, the existence of phase transition in a Cu2Se compound, the high speed of the diffusion of Cu ions, and the high vapor pressure of Se at elevated temperatures, make it necessary to carry out a series of experimental investigations to develop and optimize the methodology for obtaining the bulk material based on copper selenide. The influence of mechanochemical synthesis regimes and subsequent compaction method on the thermoelectric properties and structure of copper selenide is studied. The source material is obtained by mechanochemical synthesis. The methods of hot pressing (HP) and spark plasma synthesis (SPS) are used to obtain the bulk samples. The investigation of the structure and phase composition is performed by the X-ray diffraction and scanning electron microscopy. It is shown that increasing the duration of the mechanochemical synthesis up to 5 h leads to the depletion of copper in powders and to the formation of nonstoichiometric β-phase Cu_1.83Se, which persists after SPS. A comparison of the structure and properties of the material obtained by SPS and HP showed that the material obtained by HP has a greater degree of grain defects. The highest thermoelectric efficiency ZT = 1.8 at a temperature of 600°C is achieved for the material obtained by SPS. It is shown that low thermal conductivity is the main factor affecting the value of the thermoelectric efficiency ZT of the studied materials. The difference in the values of thermal conductivity of the materials obtained by different methods is related to the electronic component of thermal conductivity.     

Electrical Transport and Oxygen Exchange in the Superoxides of Potassium,Rubidium, and Cesium

Conductivity, ionic transference number, and chemical diffusion coefficients are determined for KO₂, RbO₂, and CsO₂. Based on such results, a defect‐chemical model is constructed. These superoxides are found to exhibit a total conductivity in the range of 3 × 10^–7 to 5 × 10^–5 S cm^–1 at 200 °C with contributions from ionic and electronic carriers. The ionic conductivity is caused by alkali interstitials and superoxide vacancies as mobile defects, and is found to exceed the n‐type electronic conductivity. ¹⁸O isotope exchange on powder samples (monitoring the gas phase composition) shows that essentially all oxygen can be exchanged. At high pO₂ this largely occurs without breaking of the O–O bond—indicating a sufficient mobility of molecular superoxide species in the solid—and with an effective rate constant that is much higher than for other large‐bandgap mixed conducting materials such as SrTiO₃.     

Synthesis and characterisation of the thallium‐substituted superconducting cuprate Hg1−xTlxBa2Ca2Cu3O8+δ

The objective of this research is the development of chemical routes for the preparation of high‐temperature superconducting powders. A simple sol–gel synthesis technique for preparing the superconducting compound Hg_1−xTl_xBa₂Ca₂Cu₃O_8+δ (Hg,Tl‐1223) has been refined. A systematic study of the influence of synthesis conditions on the phase purity of the obtained superconducting material is described. We have demonstrated that superconducting Hg_1−xTl_xBa₂Ca₂Cu₃O_8+δ phase of good quality can be obtained by this sol–gel synthesis method. Replacing Hg by Tl in the bulk material significantly increased the superconducting transition temperature. An as‐prepared sample showed T_C(onset)=136 K, but after oxygen treatment the critical temperature of Hg_1−xTl_xBa₂Ca₂Cu₃O_8+δ superconductor increased to 140 K. Copyright © 1999 John Wiley & Sons, Ltd.     

Images of a First‐Order Spin‐Reorientation Phase Transition in a Metallic Kagome Ferromagnet

First‐order phase transitions, where one phase replaces another by virtue of a simple crossing of free energies, are best known between solids, liquids, and vapors, but they also occur in a wide range of other contexts, including even elemental magnets. The key challenges are to establish whether a phase transition is indeed first order, and then to determine how the new phase emerges because this will determine thermodynamic and electronic properties. Here it is shown that both challenges are met for the spin reorientation transition in the topological metallic ferromagnet Fe₃Sn₂. The magnetometry and variable temperature magnetic force microscopy experiments reveal that, analogous to the liquid–gas transition in the temperature–pressure plane, this transition is centered on a first‐order line terminating in a critical end point in the field‐temperature plane. The nucleation and growth associated with the transition is directly imaged, indicating that the new phase emerges at the most convoluted magnetic domain walls for the high temperature phase and then moves to self‐organize at the domain centers of the high temperature phase. The dense domain patterns and phase coexistence imply a complex inhomogenous electronic structure, which can yield anomalous contributions to the electrical conductivity.     

Does Excess Energy Assist Photogeneration in an Organic Low‐Bandgap Solar Cell?

The field dependence of the photocurrent in a bilayer assembly is measured with the aim to clarify the role of excess photon energy in an organic solar cell comprising a polymeric donor and an acceptor. Upon optical excitation of the donor an electron is transferred to the acceptor forming a Coulomb‐bound electron–hole pair. Since the subsequent escape is a field assisted process it follows that photogeneration saturates at higher electric fields, the saturation field being a measure of the separation of the electron–hole pair. Using the low bandgap polymers, PCDTBT and PCPDTBT, as donors and C₆₀ as acceptor in a bilayer assembly it is found that the saturation field decreases when the photon energy is roughly 0.5 eV above the S₁–S₀ 0–0 transition of the donor. This translates into an increase of the size of the electron‐hole‐pair up to about 13 nm which is close to the Coulomb capture radius. This increase correlates with the onset of higher electronic states that have a highly delocalized character, as confirmed by quantum‐chemical calculations. This demonstrates that accessing higher electronic states does favor photogeneration yet excess vibrational energy plays no role. Experiments on intrinsic photogeneration in donor photodiodes without acceptors support this reasoning.     

Organic–Inorganic Perovskite Light‐Emitting Electrochemical Cells with a Large Capacitance

While perovskite light‐emitting diodes typically made with high work function anodes and low work function cathodes have recently gained intense interests. Perovskite light‐emitting devices with two high work function electrodes with interesting features are demonstrated here. Firstly, electroluminescence can be easily obtained from both forward and reverse biases. Secondly, the results of impedance spectroscopy indicate that the ionic conductivity in the iodide perovskite (CH₃NH₃PbI₃) is large with a value of ≈10^?8 S cm^?1. Thirdly, the shift of the emission spectrum in the mixed halide perovskite (CH₃NH₃PbI_3?xBr_x) light‐emitting devices indicates that I^? ions are mobile in the perovskites. Fourthly, this work shows that the accumulated ions at the interfaces result in a large capacitance (≈100 μF cm^?2). The above results conclusively prove that the organic–inorganic halide perovskites are solid electrolytes with mixed ionic and electronic conductivity and the light‐emitting device is a light‐emitting electrochemical cell. The work also suggests that the organic–inorganic halide perovskites are potential energy‐storage materials, which may be applicable in the field of solid‐state supercapacitors and batteries.     

Enargite Cu3PS4: A Cu–S‐Based Thermoelectric Material with a Wurtzite‐Derivative Structure

Compound semiconductors derived from ZnS (zincblende and wurtzite) with tetrahedral framework structures have functions for various applications. Examples of such materials include Cu–S‐based materials with zincblende‐derivative structures, which have attracted attention as thermoelectric (TE) materials over the past decade. This study illuminates superior TE performance in polycrystalline samples of enargite Cu₃P_1?xGe_xS₄ with a wurtzite‐derivative structure. The substitution of Ge for P dopes holes into the top of the valence band composed of Cu‐3d and S‐3p, whereby its multiband characteristic leads to a high TE power factor. Furthermore, a reduction in the grain size to 50–300 nm can effectively decrease phonon mean free paths, leading to low thermal conductivity. These features result in a dimensionless TE figure of merit ZT of 0.5 at 673 K for the x = 0.2 sample. Environmentally benign and low‐cost characteristics of the constituent elements of Cu₃PS₄, as well as its high‐performance thermoelectricity, make it a promising candidate for large‐scale TE applications. Furthermore, this finding extends the development field of Cu–S‐based TE materials to those with wurtzite‐derivative structures.     

Organo‐metal Diodes Based on a Nanoparticulate Poly(3,4‐ethylenedioxythiophene) Composite

Diodes composed of a nanoparticulate composite of poly(3,4‐ethylenedioxythiophene) and a Cu–Cu²⁺ redox couple in a poly(ethylene oxide)–LiBF₄ polymer‐electrolyte matrix between Ag and Zr electrodes show rectifications in excess of 50 000 at applied fields of 4 V. These large changes are considered to arise from both rectification at the Zr/ZrO₂ composite interface and from the switching of the composite material between two conductivity states by the application of a low potential field. The preparation and electrochemical characterisation of these novel active devices are discussed.     

“Naked” Magnetically Recyclable Mesoporous Au–γ‐Fe2O3 Nanocrystal Clusters: A Highly Integrated Catalyst System

Naked magnetically recyclable mesoporous Au–γ‐Fe₂O₃ clusters, combining the inherent magnetic properties of γ‐Fe₂O₃ and the high catalytic activity of Au nanoparticles (NPs), are successfully synthesized. Hydrophobic Au–Fe₃O₄ dimers are first self‐assembled to form sub‐micrometer‐sized Au–Fe₃O₄ clusters. The Au–Fe₃O₄ clusters are then coated with silica, calcined at 550 °C, and finally alkali treated to dissolve the silica shell, yielding naked‐Au–γ‐Fe₂O₃ clusters containing Au NPs of size 5–8 nm. The silica protection strategy serves to preserve the mesoporous structure of the clusters, inhibit the phase transformation from γ‐Fe₂O₃ to α‐Fe₂O₃, and prevent cluster aggregation during the synthesis. For the reduction of p‐nitrophenol by NaBH₄, the activity of the naked‐Au–γ‐Fe₂O₃ clusters is ≈22 times higher than that of self‐assembled Au–Fe₃O₄ clusters. Moreover, the naked‐Au–γ‐Fe₂O₃ clusters display vastly superior activity for CO oxidation compared with carbon‐supported Au–γ‐Fe₂O₃ dimers, due to the intimate interfacial contact between Au and γ‐Fe₂O₃ in the clusters. Following reaction, the naked‐Au–γ‐Fe₂O₃ clusters can easily be recovered magnetically and reused in different applications, adding to their versatility. Results suggest that naked‐Au–γ‐Fe₂O₃ clusters are a very promising catalytic platform affording high activity. The strategy developed here can easily be adapted to other metal NP–iron oxide systems.     

Large‐Scale Fabrication of MoS2 Ribbons and Their Light‐Induced Electronic/Thermal Properties: Dichotomies in the Structural and Defect Engineering

Controlled design and patterning of layered transition metal dichalcogenides (TMDs) into specific dimensions and geometries hold great potential for next‐generation micro/nanoscale electronic applications. Herein, the large‐scale fabrication of MoS₂ ribbons with widths ranging from micro‐ to nanoscale is reported. Their unique electric and thermal properties introduced by the shape change and defect creation are also demonstrated, with particular focus on the performance associated with light–matter interactions. The theoretical calculation indicates significantly increased absorption and scattering efficiency of the MoS₂ ribbons with decreasing width. As a result, enhanced photocarrier generation ability is detected on their phototransistors with defect‐modulated light‐response behavior. The light‐induced thermal transport properties of the MoS₂ ribbons are further studied. A decreased thermal conductivity is observed on narrower ribbons, attributed to the defects created during fabrication. It is also found that the effect of phonon scattering at ribbon edges on their thermal conductivity is insignificant, and the thermal transport has no obvious dependence on the ribbon direction at such width scale. This study evaluates the prospects for designing and fabricating TMD semiconductors with specific geometries for future optoelectronic applications.     

Enhanced Thermoelectric Properties of Cu2SnSe3 by (Ag,In)‐Co‐Doping

Dense bulk samples of (Ag,In)‐co‐doped Cu₂SnSe₃ have been prepared by a fast and one‐step method of combustion synthesis, and their thermoelectric properties have been investigated from 323 to 823 K. The experimental results show that Ag‐doping at Cu site remarkably enhances the Seebeck coefficient, reduces both electrical and thermal conductivities, and finally increases the figure of merit (ZT) value. The ZT of the Cu_1.85Ag_0.15SnSe₃ sample reaches 0.80 at 773 K, which is improved by about 70% compared with the unadulterated sample (ZT = 0.46 at 773 K). First principle calculation indicates that Ag‐doping changes the electronic structure of Cu₂SnSe₃ and results in larger effective mass of carriers, thus enhancing the Seebeck coefficient and reducing the electrical conductivity. The low electrical conductivity caused by Ag‐doping can be repaired by accompanying In‐doping at Sn site, and by (Ag,In)‐co‐doping the thermoelectric properties are further promoted. The (Ag,In)‐co‐doped sample of Cu_1.85Ag_0.15Sn_0.9In_0.1Se₃ shows the maximum ZT of 1.42 at 823 K, which is likely the best result for Cu₂SnSe₃‐based materials up to now. This work indicates that co‐doping may provide an effective solution to optimize the conflicting material properties for increasing ZT.     

Synthesis and Functionalization of Oriented Metal–Organic‐Framework Nanosheets: Toward a Series of 2D Catalysts

Synthesis of metal–organic frameworks (MOFs) is based on coordination‐driven self‐assembly of metal ions and organic ligands. However, to date, it remains difficult to adjust the coordination behaviors of MOFs and then control geometric shapes of nanostructures; especially their morphologies in 1D nanofibers or 2D nanosheets have seldom been explored. Here, a facile route at room temperature and ambient pressure is reported for the preparation of copper‐based MOFs with low‐dimensional shapes (i.e., nanofibers, nanorods, nanosheets, and nanocuboids), via thermodynamic and kinetic controls over the anisotropic growth. Importantly, the as‐prepared 2D MOF nanosheets with monocrystalline nature (100% exposed {010} facets) provide a material platform to the fabrication of 2D supported metal nanocatalysts. First, the MOF nanosheets can serve as a self‐templating solid precursor to prepare different CuO and CuO‐Cu₂O nanocomposites, or even Cu metals via thermolysis or reduction under controlled atmospheres. Upon their formation, second, ultrafine noble metal nanoparticles (e.g., Au, Ag, Pt, Pd, Au_0.4Pt_0.6, Au_0.4Pd_0.6, and Au_0.3Pt_0.3Pd_0.4) can be exclusively anchored on the external surfaces of the MOF nanosheets. To show their open accessibility, catalytic activities of the derived catalysts have been evaluated using CO₂ hydrogenation and 4‐nitrophenol reduction in gas phase and liquid phase, respectively.