Peiyao Yan

Hydrogels are widely applied in various fields, including energy storage and flexible electronics. However, their mechanical properties often fail to meet the requirements for long‐term and repeated deformation and full recovery. Achieving simultaneous improvement in the strength, toughness, and elasticity of hydrogels remains a significant challenge. Here, we report a nanoconfined polymerization strategy within the well‐designed, fully delaminated nanoscale covalent organic frameworks (nCOFs) that overcomes these trade‐offs. This approach yields hydrogels with an order increase in strength (from 0.3 to 3.2 MPa), a two orders enhancement in toughness (from 7.5 to 186 MJ/m ³ ) and fracture energy (from 0.8 to 14.7 kJ m ⁻² ), and a very low‐hysteresis (∼93% energy recovery) recoverable deformation even after 2000% strain in the 100 cycles. The dense entanglements provide high strength and toughness, and nanochannel‐threaded crosslinking enables large elastic deformation. Furthermore, their robust architecture affords a fivefold improvement in puncture resistance, enabling application as dendrite‐inhibiting and durable quasi‐solid‐state Zn‐ion electrolytes. This bottom‐up toughening strategy based on the nano‐reactor nCOF structural design could guide the development of next‐generation tough hydrogels for applications such as flexible energy devices and related fields.

Sulfur-sulfur bonds are ubiquitous across broad classes of natural products, peptides and proteins, drug molecules, and synthetic polymers and materials. The ability to make and break these bonds in a controlled manner is critical for their many scientific and technological applications. Here we report the discovery of an unusual S-S metathesis reaction of organic trisulfides. When exposed to certain polar aprotic solvents, trisulfides were found to undergo spontaneous metathesis, with the reaction equilibrium established in seconds in some cases. No exogenous reagents, heat, light or other stimuli were required to provoke this reaction. Furthermore, the trisulfide metathesis process can occur both inter- and intramolecularly. Understanding the scope and mechanism of this reaction enabled diverse applications of this chemistry in dynamic combinatorial library synthesis, the covalent modification of complex natural products, and S-S metathesis polymerization and depolymerization as a platform for chemically recyclable plastics.

Covalent organic frameworks (COFs) are versatile materials platforms for precise function integration owing to their high crystallinity, large surface areas, tunable characteristics and diverse and predictable structures. However, the dominant solvothermal method for COF synthesis requires harsh conditions, including high temperatures, toxic organic solvents, sealed and pressurized reactors, and extended reaction times that often exceed several days. Here we present a probe-based sonochemical method for synthesizing COFs in an aqueous environment under ambient atmosphere, offering a safer and faster alternative. By employing sonication in an aqueous acetic acid solution, the protocol avoids harmful organic solvents and high-pressure systems and reduces the reaction times to under 1 h. COFs synthesized through this method have large surface areas and high crystallinity, making them ideal for applications in photocatalysis, gas sorption, food contaminant removal and chemical sensing. The broad applicability of this synthesis method has been demonstrated by successfully preparing 62 COFs with various linkage types, including imine-linked, β-ketoenamine-linked, azine-linked and hydrazone-linked COFs, as well as frameworks with one-dimensional, two-dimensional and three-dimensional topologies. The process (performed at the 50–100 mg scale) involves steps such as preparing monomer solutions, using sonication to induce COF formation and postsynthesis purification. The surface area is characterized using nitrogen sorption, while the crystallinity is assessed by powder X-ray diffraction and transmission electron microscopy. The entire protocol can be completed within 24 h and requires moderate expertise in materials chemistry and access to standard laboratory equipment.

Structured porous materials, including metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), are being intensely developed because they can separate small molecules via precisely constructed and uniformly sized pores, despite challenges that hinder practical use. Polymers are structurally amorphous; hence, they are not considered fundamentally capable of separating different organic molecules. This manuscript reports that amorphous polymers can be prepared to separate different small organic molecules (i.e., solutes dissolved in a solvent) effectively, with very large separation factors of ~1000 and ~100,000. Effective separation involves fundamentally a delicate balance between hydrophobicity and hydrophilicity and dynamic mobility of polymeric chains to produce optimal pores. Therefore, structured pores are not fundamentally essential for molecular separation - amorphous pores are effective. These stimuli-responsive polymers have reversibly switchable states with completely opposite selectivities. They are multifunctional: they separate by polarity, size, and with opposite selectivities. Hence, they can separate many different molecules in complex solutions. These polymers are simple and inexpensive to fabricate for widespread use.

Sulfur-sulfur bonds are ubiquitous across broad classes of natural products, peptides and proteins, drug molecules, and synthetic polymers and materials. The ability to make and break these bonds in a controlled manner is critical for their many scientific and technological applications. In this study, we report the discovery of a new and unusual S-S metathesis reaction of linear organic trisulfides. When exposed to certain polar aprotic solvents, trisulfides were found to undergo spontaneous metathesis, with equilibrium established in seconds in some cases. No exogenous reagents, heat, light, or other stimuli were required to provoke this reaction. Understanding the scope and mechanism of this reaction enabled diverse applications of this chemistry in dynamic combinatorial library synthesis, covalent modification of complex natural products, and S-S metathesis polymerization and depolymerization as a platform for chemically recyclable plastics.

Inverse vulcanization has emerged as a popular strategy for transforming the waste material, elemental sulfur, into functional polymers with high sulfur content (>50 wt.%, normally). Inverse vulcanized polymers are intrinsically processable and recyclable, and have been demonstrated as promising for applications in many fields. However, the mechanical properties of inverse vulcanized polymers are currently underdeveloped. If this kind of material is to be widely used in some scenarios to replace some traditional plastics, it is necessary to make them with appropriate thermal and mechanical properties that meet basic application requirements. Here, we report a series of terpolymers copolymerized from two distinct organic comonomers and elemental sulfur to obtain polymers with a wide range of glass transition temperatures (−43 °C to 45 °C) that exhibit good mechanical properties, by blending crosslinkers with varying feed monomer ratio and chain length of linear sections, which expands the application opportunities of inverse vulcanization.

Inverse vulcanization has emerged as a popular strategy for transforming the waste material, elemental sulfur, into functional polymers with high sulfur content (>50 wt.%, normally). Inverse vulcanized polymers are intrinsically processable and recyclable, and have been demonstrated as promising for applications in many fields. However, the mechanical properties of inverse vulcanized polymers are currently underdeveloped. If this kind of material is to be widely used in some scenarios to replace some traditional plastics, it is necessary to make them with appropriate thermal and mechanical properties that meet basic application requirements. Here, we report a series of terpolymers copolymerized from two distinct organic comonomers and elemental sulfur to obtain polymers with a wide range of glass transition temperatures (-43 °C to 45 °C) that exhibit good mechanical properties, by blending crosslinkers with varying feed monomer ratio and chain length of linear sections, which expands the application opportunities of inverse vulcanization.

The inverse vulcanization (IV) of elemental sulfur to generate sulfur-rich functional polymers has attracted much recent attention. However, the harsh reaction conditions required, even with metal catalysts, constrains the range of feasible crosslinkers. We report here a photoinduced IV that enables reaction at ambient temperatures, greatly broadening the scope for both substrates and products. These conditions enable volatile and gaseous alkenes and alkynes to be used in IV, leading to sustainable alternatives for environmentally harmful plastics that were hitherto inaccessible. Density functional theory calculations reveal different energy barriers for thermal, catalytic and photoinduced IV processes. This protocol circumvents the long curing times that are common in IV, generates no H₂S by-products, and produces high-molecular-weight polymers (up to 460,000 g mol⁻¹) with almost 100% atom economy. This photoinduced IV strategy advances both the fundamental chemistry of IV and its potential industrial application to generate materials from waste feedstocks.

Inverse vulcanization, a sustainable platform, can transform sulfur, an industrial by-product, into polymers with broad promising applications such as heavy metal capture, electrochemistry and antimicrobials. However, the process usually requires high temperatures (≥159 °C), and the crosslinkers needed to stabilize the sulfur are therefore limited to high-boiling-point monomers only. Here, we report an alternative route for inverse vulcanization—mechanochemical synthesis, with advantages of mild conditions (room temperature), short reaction time (3 h), high atom economy, less H₂S, and broader monomer range. Successful generation of polymers using crosslinkers ranging from aromatic, aliphatic to volatile, including renewable monomers, demonstrates this method is powerful and versatile. Compared with thermal synthesis, the mechanochemically synthesized products show enhanced mercury capture. The resulting polymers show thermal and light induced recycling. The speed, ease, versatility, safety, and green nature of this process offers a more potential future for inverse vulcanization, and enables further unexpected discoveries.