Despite advances in the field of 2D polymerization, the synthesis of high-quality, micrometre-thick films of oriented 2D covalent organic frameworks (COFs) remains challenging. Conventional approaches focusing on thermodynamic control of the polymerization pathway face a detrimental trade-off between orientation and thickness. Here we describe a straightforward method for preparing imine-linked 2D COF films with a near-perfect face-on orientation by leveraging kinetically trapped amorphous 3D covalent adaptable network (CAN) intermediates. These off-pathway intermediates are generated as coatings through solution casting, during which the CANs spontaneously align to relax tensile stresses induced by solvent evaporation. A subsequent lift-off process, followed by an amorphous-to-crystalline transformation under solvothermal conditions, converts the 3D-oriented polymer networks into thermodynamically stable, porous and free-standing 2D COF films. This versatile kinetic trapping strategy is suitable for a range of building blocks and network topologies, constituting a convenient synthetic tool for accessing high-quality, robust, large-area 2D COF films with a strongly aligned polycrystalline structure.

Despite the advancements in the field of 2D polymerization, the synthesis of high-quality films of oriented 2D covalent organic frameworks (2D COFs) remains a longstanding challenge. Herein, we describe a method for preparing robust, large-area, porous 2D COF films with near-perfect face-on orientation via amorphous covalent adaptable network (CAN) intermediates. Generated by solution casting, the kinetically trapped CANs undergo an unusual spontaneous alignment in response to the tensile stresses emerging during the evaporation of the solvent. A subsequent amorphous-to-crystalline transformation proceeding under solvothermal conditions converts the 3D oriented networks into porous, free-standing 2D COF films. This protocol is general and suitable for a broad range of building units and network topologies, constituting a convenient synthetic tool for assembling high-quality, oriented, robust 2D COFs.

Aqueous zinc‐ion hybrid supercapacitors (Zn‐HSCs) are promising devices for sustainable and efficient energy storage. However, they suffer from a limited energy density compared to lithium‐ion batteries. This limitation can be overcome by developing novel electrode materials, with covalent organic frameworks (COFs) standing out as a particularly intriguing option. Herein, peri‐xanthenoxanthene (PXX) has been integrated for the first time into a COF scaffold to take advantage of its straightforward synthesis, chemical stability, π‐conjugated backbone, and heteroatom content endowing reversible redox reactions at low potentials. Two novel hexagonal COFs have been designed and synthesized by tethering of a PXX‐diamine unit having a C2 symmetry with two distinct tris‐aldehydes acting as C3‐symmetric cornerstones, i.e., triformyl benzene (TFB) and triformylphloroglucinol (Tp), ultimately yielding COF PXX(PhNH2)2‐TFB and COF PXX(PhNH2)2‐Tp, respectively. As cathodes in Zn‐HSCs, COF PXX(PhNH2)2‐Tp exhibits a remarkable specific capacitance, energy, and power densities (237 F g−1, 106.6 Wh kg−1, and 3.0 kW kg−1, respectively), surpassing those of COF PXX(PhNH2)2‐TFB (109 F g−1, 49.1 Wh kg−1, and 0.67 kW kg−1). Importantly, both COFs display outstanding long‐term stability, over 5000 charge/discharge cycles, with capacitance retention >92%. These findings underscore the potential of PXX‐based COFs as high‐performance cathode materials for HSCs, thereby offering a promising new avenue for energy storage technologies.

Lithium-sulphur batteries (LSBs) prevail as a viable alternative to Li-ion batteries due to their high theoretical specific capacity (1672 mA h g(S)(-1)). However, the formation of soluble polysulfides and their shuttle from the cathode to the anode cause irreversible capacity loss and uncontrolled self-discharge, limiting the performance of commercially available prototypes. In this work, we present a comparative analysis of two Kagome-shaped imine-based covalent organic frameworks (COFs) as functional modifiers for polypropylene (Celgard) separators in LSBs. We demonstrate, by using the KS60@Celgard separator modified with an optimized content of COF with the thienothiophene linker, the realization of LSBs reaching a specific discharge capacity of 850 mA h g(S)(-1) at C5. The proposed separator has an extraordinarily high Li+ diffusion coefficient (D-Li(+)) of 1.6 x 10(-7) cm(2) s(-1) at the first cathodic peak, as well as the lowest S-8 : Li2Sx content ratio in the ex situ post mortem XPS analysis. These findings demonstrate that the use of separators modified with COFs allows the mitigation of shuttle effect, and is further accompanied by an efficient oxidation of Li2Sx to S-8 (electrocatalytic effect). The equivalent K60@Celgard, based on a COF carrying a phenyl linker, results in LSBs with a specific discharge capacity of 599 mA h g(S)(-1). This work highlights the synergistic effect of polysulfide retention, selective Li+ sieving and electrocatalytic activity of COF-modified Celgard separators in the development of high-performance LSBs.

Despite the rapid progress in the field of 2D polymerisation, the fabrication of high-quality films of 2D covalent organic frameworks (2D COFs) remains a longstanding challenge. Herein, we describe a two-stage method for preparing mechanically robust, large-area, porous, highly oriented, imine-linked 2D COF films from kinetically trapped, amorphous covalent adaptable network (CAN) films. The protonated imine-linked CANs are generated by solution casting and undergo an unusual spontaneous alignment in response to the tensile stresses emerging during the evaporation of the solvent. A subsequent amorphous-to-crystalline transformation proceeding under solvothermal conditions converts the 3D oriented networks to porous, free-standing 2D COF films. This protocol is applicable to a broad range of building units and a variety of 2D COF topologies. Our results provide a convenient and general synthetic tool for the assembly of high-quality 2D COFs films suitable for the construction of molecularly precise, oriented, robust, porous materials with tailorable properties.

OECTs capable of undergoing a reversible modulation of ON current by up to 30% via irradiation with UV and visible light were realised via blending of a mixed ionic–electronic polymer (pgBTTT) and a photoswitching spiropyran derivative (OEG-SP).

Abstract The scarcity of fossil fuels calls for immediate action toward the development of clean and renewable energy resources. In this context, proton exchange membrane fuel cells (PEMFCs) are gaining ever‐increasing attention as clean technology. Although covalent organic frameworks (COFs) do not usually exhibit high intrinsic proton conductivity (σ), they have been recently proposed as solid polymer electrolytes in PEMFCs, thanks to their high crystallinity and stability to acids and bases. Here, a simple strategy is presented to improve the performance of poor COF‐based proton conductors through addition of sodium polyacrylate (PANa) superadsorbent polymer. Electrochemical impedance spectroscopy investigations after activation at high temperature and relative humidity (RH) provide insights into the role of PANa, whose presence is key to preserve high σ at low RH. The humidity‐dependent X‐ray diffraction study reveals a strengthening of the stacking interaction along the COF (100) plane direction with increasing humidity, through the formation of H‐bonding, thus promoting proton hopping. The study of the dielectric properties as a function of PANa content enables to determine a Debye relaxation regime for the COF/PANa blend with a maximum relaxation frequency of 1513 and 6606 Hz for the pristine COF and the COF/PANa blend, respectively, at their maximum operating temperatures.

The coupling of different 2D materials (2DMs) to form van der Waals heterostructures (vdWHs) is a powerful strategy for adjusting the electronic properties of 2D semiconductors, for applications in opto-electronics and quantum computing. 2D molybdenum disulfide (MoS2 ) represents an archetypical semiconducting, monolayer thick versatile platform for the generation of hybrid vdWH with tunable charge transport characteristics through its interfacing with molecules and assemblies thereof. However, the physisorption of (macro)molecules on 2D MoS2 yields hybrids possessing a limited thermal stability, thereby jeopardizing their technological applications. Herein, the rational design and optimized synthesis of 2D covalent organic frameworks (2D-COFs) for the generation of MoS2 /2D-COF vdWHs exhibiting strong interlayer coupling effects are reported. The high crystallinity of the 2D-COF films makes it possible to engineer an ultrastable periodic doping effect on MoS2 , boosting devices' field-effect mobility at room temperature. Such a performance increase can be attributed to the synergistic effect of the efficient interfacial electron transfer process and the pronounced suppression of MoS2 's lattice vibration. This proof-of-concept work validates an unprecedented approach for the efficient modulation of the electronic properties of 2D transition metal dichalcogenides toward high-performance (opto)electronics for CMOS digital circuits.

Imine-based covalent organic frameworks (COFs) are a widely studied class of functional, crystalline, and porous nanostructures which combine a relatively facile crystallization with tuneable compositions and porosities. However, the imine linkage constitutes an intrinsic limitation due to its reduced stability in harsh chemical conditions and its unsuitability for in-plane π-conjugation in COFs. Urgent solutions are therefore required in order to exploit the full potential of these materials, thereby enabling their technological application in electronics, sensing, and energy storage devices. In this context, the advent of a new generation of linkages derived from the chemical conversion and locking of the imine bond represents a cornerstone for the synthesis of new COFs. A marked increase in the framework robustness is in fact often combined with the incorporation of novel functionalities including, for some of these reactions, an extension of the in-plane π-conjugation. This Minireview describes the most enlightening examples of one-pot reactions and post-synthetic modifications towards the chemical locking of the imine bond in COFs.

The development of efficient homogeneous catalysts for the synthesis of functionalized polyolefins is a challenging topic. Palladium(II) complexes with alpha-diimine ligands having a phenanthrene skeleton and 2,6-disubstituted aryl rings (Ar-BIP) were synthesized, characterized, and tested as precatalysts in the copolymerization of ethylene with methyl acrylate. The direct comparison with analogous complexes having the corresponding alpha-diimines with an acenaphthene skeleton (Ar-BIAN) was performed. X-ray characterization in the solid state and NMR analysis in solution of both neutral [Pd(Ar-BIP)(CH3)Cl] and monocationic [Pd(Ar-BIP)(CH3)(NCCH3)][PF6] complexes indicate that the Ar-BIP ligands have a higher Lewis basicity and are more strongly coordinated to the metal center in comparison to the Ar-BIAN counterparts. Therefore, the Pd(Ar-BIP) cationic complexes can be regarded as electron-rich metal cations. In addition, they create a higher steric congestion around palladium in comparison to Ar-BIAN, regardless of the substituents on the aryl rings. The monocationic species generate active catalysts for the ethylene/methyl acrylate copolymerization leading to copolymers with M-n values up to 37000 and a content of polar monomer of 5.3 mol %. A detailed study of the catalytic behavior points out that Pd(Ar-BIP) catalysts show a good affinity for the polar monomer, have a good thermal stability, and favor the cleavage of the catalyst resting state, leading to copolymers with M-w values higher than those of the macromolecules produced with the corresponding Pd(Ar-BIAN) under the same reaction conditions. NMR characterization of the produced copolymers points out that the polar monomer is inserted both at the end of the branches and into the main chain, with an enchainment more selective than that achieved when the copolymerization is carried out in dichloromethane. In situ NMR investigations allowed us to detect relevant intermediates of the catalytic cycle and shed light on the nature of possible deactivated species.