Changwen Hu

Cationic covalent organic frameworks (COFs) hold great potential for ion conduction and catalysis, yet poor crystallinity from interlayer electrostatic repulsion severely limits their performance. Herein, we demonstrate that lattice‐matched polyoxometalates (POMs) as multifunctional counterions can direct the crystallization of cationic COFs and introduce functional sites. In situ incorporation of Keggin‐type POMs affords highly crystalline honeycomb frameworks (POM@vCOF‐CR), whereas post‐synthetic ion exchange yields amorphous materials. Further investigations reveal that POMs play multiple roles during the crystallization process: in‐plane, they modulate monomer release to promote ordered growth; out‐of‐plane, they act as electrostatic anchoring centers to facilitate ordered stacking. Crucially, lattice‐matching between the POM sublattice and the COF framework eliminates configurational degeneracy and dictates long‐range ordering. This principle is further validated in a square‐lattice pvCOF, where only the larger Preyssler‐type POM can form a matched square sublattice that enables crystallization, whereas smaller Keggin‐type POMs lead to orientational disorder and amorphous products. Benefiting from the ordered functional sites and transport pathways, the crystalline POM@vCOF‐CR exhibits significantly enhanced electrocatalytic activity for ethylbenzene oxidation and improved lithium‐ion conductivity compared to its amorphous counterpart. This work establishes a rational solution for constructing crystalline cationic COFs by using lattice‐matched POMs, thereby enabling functional frameworks with enhanced performance.

Lignocellulosic biomass, consisting of lignin, cellulose, and hemicellulose, represents a major renewable resource, and its efficient utilization is central to green and sustainable chemistry. Polyoxometalates (POMs) have emerged as versatile catalysts for biomass valorization owing to their tunable Brønsted acidity/basicity, redox properties, and unique electron/proton storage capability. This review provides a comprehensive overview of recent advances in POM-catalyzed lignocellulosic biomass conversion, with particular emphasis on lignin depolymerization and the selective conversion of hemicellulose- and cellulose-derived platform molecules, namely furfural (FF) and 5-hydroxymethylfurfural (HMF). For lignin depolymerization, the catalytic roles of different POM families are systematically discussed. For the valorization of FF and HMF, particular attention is devoted to their selective oxidative and reductive transformations. This review encompasses a broad range of POM catalysts, including classical POMs and their cation-modified derivatives, supported POM materials, and structurally novel POM architectures, and highlights how their intrinsic properties govern reaction pathways, product selectivity, and reaction mechanisms under thermal, photocatalytic, and electrocatalytic conditions. Finally, current challenges and future opportunities for biomass valorization using POM-based catalytic systems are discussed.

The first polyoxoniobate featuring the long-sought face-sharing octahedra, as observed in natural minerals, has been successfully synthesized using highly charged Te( iv ) ions.

Single-cluster polyoxometalate catalysts on cationic COFs via electrostatic assembly enable modular design and high activity for furfural electroreduction.

An open hollow polyoxovanadate cage, V14Nb2P8, based on {Nb(V ₅ )} pentagons can encapsulate Cs ⁺ ions through its opening and accommodation of organic molecules within its cavity.

The oxidative conversion of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) is an important reaction for the utilization of biomass resources. This process has garnered considerable research attention in both industry and academia, yet it still presents considerable challenges. To achieve an effective and mild oxidative upgrade of the HMF molecule, a multiorganic-ligand-functionalized polyoxovanadate catalyst, V₆O₆(OCH₃)₄(mIM)₆(C₆H₅PO₃)₄ (P₄V₆), has been successfully prepared by using both oxygen- and nitrogen-containing ligands. P₄V₆, characterized by its unique candy-like structure, demonstrates remarkable catalytic performance in converting HMF, achieving 95% conversion and 94% selectivity toward DFF under an O₂ atmosphere. Furthermore, P₄V₆ exhibits good stability and can be reused over five consecutive cycles without any substantial changes to its structure and catalytic performance. Comprehensive mechanistic investigations, supported by control experiments, kinetic studies, and spectral analyses, indicate a plausible four-step catalytic mechanism. This work provides a new perspective on the design of polyoxovanadate-based catalysts for biomass valorization.

Co-CoO _x /N-doped carbon combined with the recyclable base K ₇ HNb ₆ O ₁₉ synergistically catalyze the selective and rapid cleavage of lignin β-O-4 models into aromatic products.

[PIMPS]₃PW₁₂O₄₀ was used as a reversible phase transformation-type catalyst for the thiolation of alcohols to synthesize a series of benzyl thioethers and exhibited high activity and good recyclability.

Polyoxovanadates (POVs) have received widespread attention in catalytic applications due to their various structures and remarkable redox properties. By introducing a second transition metal, POV-based inorganic–organic hybrid (POVH) catalysts show increasing stability and more catalytic active sites compared with pure POVs. In this perspective article, POVH materials as oxidative catalysts have been classified into two main categories according to the interactions between transition metal-complex units and POV clusters: (i) hybrids with metal–organic units act as isolated cations and (ii) hybrids with an organic ligand coordinate to the second transition metal, which is further linked to a POV cluster via oxygen bridges directly or indirectly to give zero-, one-, two- or three-dimensional supramolecular structures. The oxidative conversion of organic compounds, including thiophene derivatives, thioethers, alkanes, alcohols, and alkenes, and oxidative detoxification of a sulfur mustard simulant or degradation of lignin, along with the oxidative photo/electrocatalytic transformation of organic compounds catalyzed by POVH materials, are discussed in detail. Furthermore, the challenges and prospects toward the development of POVH catalysts are explored briefly from our perspectives.