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Large‐scale and low‐cost synthesis of covalent organic frameworks (COFs) to meet the demands of industrial application remains formidably challenge. Here we report using 2,4,6‐collidine as monomer to produce a series of highly crystalline olefin‐linked COFs by a melt polymerization method. This method enables the kilogram‐scale fabrication of self‐shaped monolithic robust foams. The afforded COFs possess extremely low cost (<50 USD/kg), superior to all the reported COFs. Furthermore, using one‐pot or post‐modification methods can conveniently transform neutral COFs to ionic COFs, which can be applied as highly efficient ion‐exchange sorbents for scavenging oxoanion pollutants. Remarkably, the superior adsorption capacity of a model oxoanion (ReO4−) is the highest among crystalline porous materials reported so far. This work not only expands the scopes of olefin‐linked COFs but also enlightens the route for the industrial production of crystalline ion exchange sorbents. [ABSTRACT FROM AUTHOR]

Fabricating mechanically responsive actuators that can efficiently convert external stimuli into mechanical work is of great significance for real‐world applications. Herein, we rationally design a class of rigid–flexible coupling crystalline crosslinked polymers (CCPs) to fabricate vapomechanically responsive actuators. Interfacial condensation reactions of flexible macromers with rigid monomers afford a series of freestanding CCP membranes. Notably, it is the first example where crosslinked polymers show high crystallinity and porosity. Moreover, the CCP membranes exhibit good mechanical properties and interesting vapor‐triggered actuation performance, which is reversible and repeatable. We find that the unusual polymer structures, high vapor sorption, and anisotropic membranes contribute to the directional deformation performance of the CCP actuators. The synthesis approach in this work provides new insights into the design and fabrication of smart materials for advanced applications. [ABSTRACT FROM AUTHOR]

Traditional ozone sensing and removal materials still suffer from high energy consumption and low efficiency. Thus, seeking new ozone‐responsive materials with high efficiency and broad working conditions is of great significance. Herein, we first developed covalent organic frameworks (COFs) for smart sensing and efficient removal of ozone. Notably, imine‐based COFs possess dramatically fast optical responses (<1 s) to ozone as low as 0.1 ppm under broad working conditions (e.g., in the presence or absence of moisture, room temperature). Moreover, we found that imine‐based COFs can also be applied as excellent ozone removers that can efficiently reduce the ozone concentration below the recommended safety limit (<0.1 ppm) for humans. The mechanism for the performance of imine‐based COFs was unveiled in‐depth by various characterization techniques and analyses. This study not only provides a new type of advanced materials for ozone sensing and removal but also broadens the application scope of COFs. [ABSTRACT FROM AUTHOR]

Abstract: It is still a challenge to achieve both excellent mechanical strength and biocompatibility in hydrogels. In this study, we exploited two interactions to form a novel biocompatible, slicing‐resistant, and self‐healing hydrogel. The first was molecular host–guest recognition between a host (isocyanatoethyl acrylate modified β‐cyclodextrin) and a guest (2‐(2‐(2‐(2‐(adamantyl‐1‐oxy)ethoxy)ethoxy)ethoxy)ethanol acrylate) to form “three‐arm” host–guest supramolecules (HGSMs), and the second was covalent bonding between HGSMs (achieved by UV‐initiated polymerization) to form strong cross‐links in the hydrogel. The host–guest interaction enabled the hydrogel to rapidly self‐heal. When it was cut, fresh surfaces were formed with dangling host and guest molecules (due to the breaking of host–guest recognition), which rapidly recognized each other again to heal the hydrogel by recombination of the cut surfaces. The smart hydrogels hold promise for use as biomaterials for soft‐tissue repair. [ABSTRACT FROM AUTHOR]

The construction of olefin‐linked chiral covalent organic frameworks (COFs) with high crystallinity is highly desirable while remains great challenge due to the poor reversibility of the formation reaction for the olefin linkages during the in situ structural self‐healing process. Herein, we successfully synthesized two sets of enantiomeric olefin‐linked COFs. The chiral catalytic groups are uniformly distributed on the pore walls of COFs, resulting in the full exposure of catalytic sites to the reactants in asymmetric catalysis. The as‐prepared (R)/(S)‐CCOF8 exhibits excellent catalytic performance with exceeding 99 % enantiomeric excess in the enantioselective electrophilic amination reaction. Moreover, the heterogeneous chiral catalysts are conveniently recycled and could maintain the performance after ten catalytic cycles. Our findings expand the scope to construct stable and crystalline chiral COFs for the asymmetric catalysis. [ABSTRACT FROM AUTHOR]

Regarding the global energy crisis, it is of profound significance to develop spontaneous power generators that harvest natural energy. Fabricating humidity‐responsive actuators that can conduct such energy transduction is of paramount importance. Herein, we incorporate covalent organic frameworks with flexible polyethylene glycol to fabricate rigid‐flexible coupled membrane actuators. This strategy significantly improves the mechanical properties and humidity‐responsive performance of the actuators, meanwhile, the existence of ordered structures enables us to unveil the actuation mechanism. These high‐performance actuators can achieve various actuation applications and exhibit interesting self‐oscillation behavior above a water surface. Finally, after being coupled with a piezoelectric film, the bilayer device can spontaneously output electricity over 2 days. This work paves a new avenue to fabricate rigid‐flexible coupled actuators for self‐sustained energy transduction. [ABSTRACT FROM AUTHOR]

Coordination‐driven crosslinking networks with reversible and dynamic characteristics are gaining increasing interest in diverse application fields. Herein, we use a coordination crosslinking approach using metal‐organic polyhedra (MOPs) as high‐connectivity building blocks to post‐assemble a class of coordination hypercrosslinked MOP (CHMOP) polymers. The introduction of 12‐connected MOP nodes to the polymeric networks is critical to producing membranes that overcome the trade‐off between mechanical properties and dynamic healing, and meanwhile possess multifunctionalities including shape memory, solution processability, and 3D printing. The CHMOPs can also be used for anticorrosion coating and achieve function couplings, e.g. shape memory‐assisted self‐healing (SMASH), which have not been achieved in the MOP‐based hybrid materials yet. This work not only offers a feasible strategy to construct new multifunctional materials but also greatly expands the application scopes of MOPs. [ABSTRACT FROM AUTHOR]