A Visible‐Light‐Induced Dynamic Mechanical Bond as a Linkage for Dynamic Materials

Exploring dynamic bonds and their applications in fabricating dynamic materials has received great attention. A photoinduced [2]rotaxane‐based dynamic mechanical bond (DMB) features visible‐light‐triggered dynamic bonding behavior that is essentially distinguished from conventional dynamic chemical bonds. In this DMB, a photoisomerizable ortho‐fluoroazobenzene unit is introduced as a steric‐controllable stopper, the visible‐light‐induced dynamic wagging movement of which enables the photoregulated threading of the macrocycle. This allows reversible in situ de‐/reforming of the mechanical bond without involving dynamic chemical linkage. The DMB‐cross‐linked polymeric gel shows interesting photoinduced degradation behavior upon visible light irradiation. Benefiting from the distinctive dual dynamic nature of reversible bonding behavior and mechanical interlocked structure, this DMB is expected to serve as a new type of dynamic bond that can be applied in designing dynamic soft materials.     

Promoting Frustrated Lewis Pairs for Heterogeneous Chemoselective Hydrogenation via the Tailored Pore Environment within Metal–Organic Frameworks

Frustrated Lewis pairs (FLPs) have recently been advanced as efficient metal‐free catalysts for catalytic hydrogenation, but their performance in chemoselective hydrogenation, particularly in heterogeneous systems, has not yet been achieved. Herein, we demonstrate that, via tailoring the pore environment within metal–organic frameworks (MOFs), FLPs not only can be stabilized but also can develop interesting performance in the chemoselective hydrogenation of α,β‐unsaturated organic compounds, which cannot be achieved with FLPs in a homogeneous system. Using hydrogen gas under moderate pressure, the FLP anchored within a MOF that features open metal sites and hydroxy groups on the pore walls can serve as a highly efficient heterogeneous catalyst to selectively reduce the imine bond in α,β‐unsaturated imine substrates to afford unsaturated amine compounds.     

Dynamic Covalent Chemistry within Biphenyl Scaffolds: Reversible Covalent Bonding,Control of Selectivity,and Chirality Sensing with a Single System

Axial chirality is a prevalent and important phenomenon in chemistry. Herein we report a combination of dynamic covalent chemistry and axial chirality for the development of a versatile platform for the binding and chirality sensing of multiple classes of mononucleophiles. An equilibrium between an open aldehyde and its cyclic hemiaminal within biphenyl derivatives enabled the dynamic incorporation of a broad range of alcohols, thiols, primary amines, and secondary amines with high efficiency. Selectivity toward different classes of nucleophiles was also achieved by regulating the distinct reactivity of the system with external stimuli. Through induced helicity as a result of central‐to‐axial chirality transfer, the handedness and ee values of chiral monoalcohol and monoamine analytes were reported by circular dichroism. The strategies introduced herein should find application in many contexts, including assembly, sensing, and labeling.     

Significant Enhancement of C2H2/C2H4 Separation by a Photochromic Diarylethene Unit: A Temperature‐ and Light‐Responsive Separation Switch

A dual temperature‐ and light‐responsive C₂H₂/C₂H₄ separation switch in a diarylethene metal–organic framework (MOF) is presented. At 195 K and 100 kPa this MOF shows ultrahigh C₂H₂/C₂H₄ selectivity of 47.1, which is almost 21.4 times larger than the corresponding value of 2.2 at 293 K and 100 kPa, or 15.7 times larger than the value of 3.0 for the material under UV at 195 K and 100 kPa. The origin of this unique control in C₂H₂/C₂H₄ selectivity, as unveiled by density functional calculations, is due to a guest discriminatory gate‐opening effect from the diarylethene unit.     

Enantioselective Direct Mannich‐Type Reactions Catalyzed by Frustrated Lewis Acid/Brønsted Base Complexes

An enantioselective direct Mannich‐type reaction catalyzed by a sterically frustrated Lewis acid/Brønsted base complex is disclosed. Cooperative functioning of the chiral Lewis acid and achiral Brønsted base components gives rise to in situ enolate generation from monocarbonyl compounds. Subsequent reaction with hydrogen‐bond‐activated aldimines delivers β‐aminocarbonyl compounds with high enantiomeric purity.     

Expanding the Boundaries of Water‐Tolerant Frustrated Lewis Pair Hydrogenation: Enhanced Back Strain in the Lewis Acid Enables the Reductive Amination of Carbonyls

The development of a boron/nitrogen‐centered frustrated Lewis pair (FLP) with remarkably high water tolerance is presented. As systematic steric tuning of the boron‐based Lewis acid (LA) component revealed, the enhanced back‐strain makes water binding increasingly reversible in the presence of relatively strong base. This advance allows the limits of FLP's hydrogenation to be expanded, as demonstrated by the FLP reductive amination of carbonyls. This metal‐free catalytic variant displays a notably broad chemoselectivity and generality.     

Designed Synthesis of a 2D Porphyrin‐Based sp2 Carbon‐Conjugated Covalent Organic Framework for Heterogeneous Photocatalysis

The construction of stable covalent organic frameworks (COFs) for various applications is highly desirable. Herein, we report the synthesis of a novel two‐dimensional (2D) porphyrin‐based sp² carbon‐conjugated COF (Por‐sp²c‐COF), which adopts an eclipsed AA stacking structure with a Brunauer—Emmett—Teller surface area of 689 m² g^?1. Owing to the C=C linkages, Por‐sp²c‐COF shows a high chemical stability under various conditions, even under harsh conditions such as 9 m HCl and 9 m NaOH solutions. Interestingly, Por‐sp²c‐COF can be used as a metal‐free heterogeneous photocatalyst for the visible‐light‐induced aerobic oxidation of amines to imines. More importantly, in comparison to imine‐linked Por‐COF, the inherent structure of Por‐sp²c‐COF equips it with several advantages as a photocatalyst, including reusability and high photocatalytic performance. This clearly demonstrates that sp² carbon‐linked 2D COFs can provide an interesting platform for heterogeneous photocatalysis.     

An Olefin‐Linked Covalent Organic Framework as a Flexible Thin‐Film Electrode for a High‐Performance Micro‐Supercapacitor

Developing effective synthetic strategies as well as enriching functionalities for sp²‐carbon‐linked covalent organic frameworks (COFs) still remains a challenge. Now, taking advantage of a variant of Knoevenagel condensation, a new fully conjugated COF ( g‐C₃₄N₆‐COF ) linked by unsubstituted C=C bonds was synthesized. Integrating 3,5‐dicyano‐2,4,6‐trimethylpyridine and 1,3,5‐triazine units into the molecular framework leads to the enhanced π‐electron communication and electrochemical activity. This COF shows uniform nanofibrous morphology. By assembling it with carbon nanotubes, a flexible thin‐film electrode for a micro‐supercapacitor (MSC) can be easily obtained. The resultant COF‐based MSC shows an areal capacitance of up to 15.2 mF cm^?2, a high energy density of up to 7.3 mWh cm^?3, and remarkable rate capability. These values are among the highest for state‐of‐the‐art MSCs. Moreover, this device exhibits excellent flexibility and integration capability.     

A Versatile Dynamic Mussel‐Inspired Biointerface: From Specific Cell Behavior Modulation to Selective Cell Isolation

Reported here is a novel dynamic biointerface based on reversible catechol‐boronate chemistry. Biomimetically designed peptides with a catechol‐containing sequence and a cell‐binding sequence at each end were initially obtained. The mussel‐inspired peptides were then reversibly bound to a phenylboronic acid (PBA) containing polymer‐grafted substrate through sugar‐responsive catechol‐boronate interactions. The resultant biointerface is thus capable of dynamic presentation of the bioactivity (i.e. the cell‐binding sequence) by virtue of changing sugar concentrations in the system (similar to human glycemic volatility). In addition, the sugar‐responsive biointerface enables not only dynamic modulation of stem cell adhesion behaviors but also selective isolation of tumor cells. Considering the highly biomimetic nature and biological stimuli‐responsiveness, this mussel‐inspired dynamic biointerface holds great promise in both fundamental cell biology research and advanced medical applications.     

Decoupled Thermo‐ and pH‐Responsive Hydrogel Microspheres Cross‐Linked by Rotaxane Networks

Rotaxane cross‐linked (RC) microgels that exhibit a decoupled thermo‐ and pH‐responsive volume transition were developed. The pH‐induced changes of the aggregation/disaggregation states of cyclodextrin in the RC networks were used to control the swelling capacity of the entire microgels. Different from conventional thermo‐ and pH‐responsive microgels, which are usually obtained from copolymerizations involving charged monomers, the RC microgels respond to temperature as intended, even in the presence of charged functional molecules such as dyes in the microgel dispersion. The results of this study should lead to new applications, including drug delivery systems that require a retention of their smart functions even in environments that may contain foreign ions, for example, in in vivo experiments.     

Fully Conjugated Two‐Dimensional sp2‐Carbon Covalent Organic Frameworks as Artificial Photosystem I with High Efficiency

The synthesis of fully conjugated sp²‐carbon covalent organic frameworks (COF) is extremely challenging given the difficulty of the formation of very stable carbon‐carbon double bonds (‐C=C‐). Here, we report the successful preparation of a 2D COF (TP‐COF) based on triazine as central planar units bridged by sp²‐carbon linkers through the ‐C=C‐ condensation reaction. High‐resolution‐transmission electron microscopy (HRTEM) clearly confirmed the tessellated hexagonal pore structure with a pore center‐to‐center distance of 2 nm. Powder X‐ray diffraction (PXRD) together with structural simulations revealed an AA stacking mode of the obtained layered structure. TP‐COF turned out to be an excellent semiconductor material with a LUMO energy of ?3.23 eV and a band gap of 2.36 eV. Excitingly, this novel sp²‐carbon conjugated TP‐COF exhibited unprecedented coenzyme regeneration efficiency and can significantly boost the coenzyme‐assisted synthesis of l ‐glutamate to a record‐breaking 97 % yield within 12 minutes.     

H2S‐Activable MOF Nanoparticle Photosensitizer for Effective Photodynamic Therapy against Cancer with Controllable Singlet‐Oxygen Release

Photodynamic therapy (PDT) has emerged as an important minimally invasive tumor treatment technology. The search for an effective photosensitizer to realize selective cancer treatment has become one of the major foci in recent developments of PDT technology. Controllable singlet‐oxygen release based on specific cancer‐associated events, as another major layer of selectivity mode, has attracted great attention in recent years. Here, for the first time, we demonstrated that a novel mixed‐metal metal–organic framework nanoparticle (MOF NP) photosensitizer can be activated by a hydrogen sulfide (H₂S) signaling molecule in a specific tumor microenvironment for PDT against cancer with controllable singlet‐oxygen release in living cells. The effective removal of tumors in vivo further confirmed the satisfactory treatment effect of the MOF NP photosensitizer.     

A Hydrogen‐Bonded Hexagonal Buckybowl Framework

A hydrogen‐bonded two‐dimensionally networked buckybowl architecture is presented. Two types of hexagonal network (HexNet) structures ( CPSM‐1 and CPSM‐2 ) have been achieved based on a sumanene derivative ( CPSM ) possessing 4,4′‐dicarboxy‐o ‐terphenyl groups in the periphery. CPSM‐1 has a waved HexNet structure with an alternate alignment of upward and downward bowls. CPSM‐2 has a bilayered HexNet structure composed of hamburger‐shaped dimers of the bowls. This demonstrates that non‐planar π‐systems can be networked two‐dimensionally by an appropriate supramolecular synthon to achieve structurally well‐defined unique bumpy π‐sheets. Furthermore, we revealed that CPSM‐2 undergoes anisotropic shrinking along the c axis by 11 % under high pressure conditions (970 MPa). The shrinkage is brought about by offset sliding between bumpy π‐surfaces of the bilayered HexNet sheets.