Jianghua He

The development of neutral silicon-based Lewis acids (LAs) has gained increasing attention, their use as catalysts for polymerization reactions has not yet been reported. Herein, we report a neutral silicon-based Lewis pair (LP) catalytic system composed of Si(catR)2 (R = H, Cl, Br, tBu) LAs and N-heterocyclic olefin (NHO) for the living polymerization of acrylamide monomers. The coordination behavior between monomers and Si(catR)2 with varying Lewis acidities was elucidated by single-crystal X-ray diffraction and in situ NMR analysis. The Si(catH)2/NHO pair exhibited high catalytic activity and control under ambient conditions, enabling the polymerization of N,N-dimethylacrylamide with high molecular weights (up to 576 kg·mol–1) and low dispersities (Đ = 1.13–1.22). MALDI-TOF-MS and chain-extension studies confirmed the living nature of the system. The scope was extended to other acrylamides, including N,N-diethylacrylamide and N,N-diallylacrylamide, allowing the synthesis of well-defined block copolymers with preserved pendant functionality and clear microphase separation behavior as confirmed by DSC. This work constructs a metal-free neutral silicon-based Lewis pair catalytic platform dedicated to the controlled synthesis of polyacrylamides, expands the library of main-group Lewis pair catalysts, and offers a novel synthetic strategy for fabricating functional precision polymers available for postpolymerization modification.

A simple way to access a series of novel potential organic intermediates, C3-stannyl tetrahydroquinolines, by employing hydroborane and hydrostannane as co-reductants to reduce quinoline catalyzed by B(C₆F₅)₃.

The development of modern society is closely related to polymer materials. However, the improper disposal of the polymer wastes not only squanders resources but also intensifies the environmental issues, despite that energy recovery, physical recycling and chemical recycling pathways have been developed to tackle the recycle and reuse of polymers. Among them, chemical recycling is considered as the most pivotal solution, as it can depolymerize the polymer wastes back to monomers, which then repolymerize into polymer materials. Recently, remarkable progress has been made in the development of chemically recyclable polymers through monomer design to shift “polymerization-depolymerization” equilibrium to realize the selective depolymerization of the polymers into monomers, and to achieve chemical recycling closed-loop. This article reviews the closed-loop polymers such as polyesters, polycarbonates, sulfur-containing polymers, vinyl monomer-based polymers as well as other types of polymers. Moreover, the challenges and prospects in this field are also discussed.

Being a versatile platform for the production of functional polymers, vinyl-containing polymers are difficult to synthesize through traditional living polymerization techniques, which typically require strict control over reaction conditions to prevent crosslinking. Herein, we employed living/controlled Lewis pair polymerization (LPP) to transform allyl methacrylate into soluble poly­(allyl methacrylate) with high molecular weights (up to M _n = 1143 kg/mol) and narrow molecular weight distributions (Đ = 1.07–1.32), leaving vinyl pendants intact in every repeat unit. Well-defined block or random copolymers can be synthesized through the regulation of the position and density of the pendent vinyl sites on polymer chains. In combination with thiol–ene click reactions, different types of functional groups could be introduced to the polymeric framework, furnishing various functionalized polymers with different topologies, including photo-responsive, self-healing, or amphiphilic linear polymers, graft plastics, and cross-linked elastomers with enhanced strength and toughness. This strategy enables the preparation of vinyl-containing polymers with adjustable architectures, exhibiting promising application potentials in the synthesis of functional materials.

It is an attractive but formidable challenge in the chemical recycling of polystyrene (PS) wastes to the value-added aromatic compounds due to the inertness of C-C bonds in polymer backbone. Here we develop a light-driven, copper-catalyzed protocol to achieve aerobic oxidation of various alkylarenes or real-life PS wastes to benzoic acid and oxidized styrene oligomers. The resulting oligomers can be further transformed under heating condition, thus achieving benzoic acid in up to 65% total yields through an integrated one-pot two-step procedure. Mechanistic studies show that the CuCl₂ catalyst undergoes Ligand-to-Metal Charge Transfer (LMCT) to generate a chlorine radical, which triggers the activation of C-H bond and subsequent oxidative cleavage of C-C bonds. The practicality and scalability of this strategy are demonstrated by depolymerization of real-life PS foam on a gram scale, thus showing promising application potentials in chemical recycling of PS wastes.

It is challenging to realize the selective C−C bond cleavage of lignin β‐O‐4 linkages for production of high‐value aromatic chemicals due to its intrinsic inertness and complex structure. Here we report a light‐driven, chlorine‐radical‐based protocol to realize the oxidative C−C bond cleavage in various lignin model compounds catalyzed by commercially available TPT and CaCl₂, achieving high conversion and good to high product yields at room temperature. Mechanistic studies reveal that the preferential activation of C_β−H bond facilitates the oxidation and C−C bond cleavage of lignin β‐O‐4 model via chlorine radical. Furthermore, this method is also applicable to the depolymerization of natural lignin extracts, furnishing the aromatic oxygenates from the cleavage of C_α−C_β bonds. This study provides experimental foundations to the depolymerization and valorization of lignin into high value‐added aromatic compounds.

Background: Hepatocellular carcinoma (HCC) is one of the most common malignancies with a high lethality rate. ZMIZ2 is a transcriptional co-activator implicated in various human diseases. However, the role and molecular mechanism of ZMIZ2 in HCC remains to be elucidated. Methods: The expression and prognostic value of ZMIZ2 in HCC was excavated from public databases and explored by bioinformatic analysis. Then the expression of ZMIZ2 and related genes was further validated by quantitative RT-PCR, western blotting, and immunohistochemistry. Loss and gain-of-function experiments were performed in vitro and in vivo to investigate the function of ZMIZ2 in HCC. In addition, transcriptome sequencing and immunoprecipitation was conducted to explore the potential molecular mechanisms of ZMIZ2. Results: ZMIZ2 was highly expressed in HCC and associated with poor prognosis. Silencing ZMIZ2 significantly inhibited HCC cell proliferation, cell cycle process, migration, and invasion in vitro, and also inhibited the progression of HCC in vivo. Additionally, ZMIZ2 expression was correlated with immune cell infiltration in HCC samples. Somatic mutation analysis showed that ZMIZ2 and TP53 mutations jointly affected the progression of HCC. Mechanistically, ZMIZ2 interacted with LEF1 to regulate malignant progression of HCC by activating the Wnt/β-catenin pathway. Conclusion: ZMIZ2 was overexpressed in HCC and associated with poor prognosis. The overexpression of ZMIZ2 was corelated with malignant phenotype, and it facilitated HCC progression via LEF1-mediated activation of the Wnt/β-catenin pathway. Furthermore, ZMIZ2 could be served as a prognostic biomarker and a new therapeutic target for HCC.