Three new Si-substituted polyoxovanadates (POVs), [Cd₂(dien)₂][Cd(dien)][Cd(Hdien)₂][V₁₅Si₆O₄₆(OH)₂(H₂O)]·7H₂O (1), [Co(enMe)₂]₃[Co₂(enMe)₂(H₂O)₂][V₁₆Si₄O₄₄(OH)₂(H₂O)]·6H₂O (2), and [Co(teta)]₄[V₁₆Si₄O₄₂(OH)₄(H₂O)]·10H₂O (3) (dien = diethylenetriamine; enMe = 1,2-diaminopropane; teta = triethylenetetramine) were synthesized by the hydrothermal method and characterized. Structural analysis sheds light on the fact that the {V₁₅Si₆O₄₈}/{V₁₆Si₄O₄₆} clusters of compounds 1–3 were formed by replacing {VO₅} square pyramids in the classical {V₁₈O₄₂} cluster with {Si₂O₇} units. Compound 1 is a 2D bilayer structure formed by the [V₁₅Si₆O₄₆(OH)₂(H₂O)]¹⁰⁻ cluster and two types of bridging Cd complexes containing binuclear groups [Cd₂(dien)₂]⁴⁺. Compound 2 is a 3D framework constructed from the [V₁₆Si₄O₄₄(OH)₂(H₂O)]¹⁰⁻ cluster and two types of Co complex fragments including binuclear [Co₂(enMe)₂(H₂O)₂]⁴⁺. In compound 3, the [V₁₆Si₄O₄₂(OH)₄(H₂O)]⁸⁻ cluster is connected with bridging [Co(teta)]²⁺ to expand into a 2D network. Compounds 1 and 3 represent the first 2D assemblies based on a vanadosilicate cluster. 1–3 served as heterogeneous catalysts and exhibited highly efficient catalytic activities for the Knoevenagel condensation under mild ambient conditions with low catalyst loading, featuring the open Lewis base {V₁₅Si₆O₄₈}/{V₁₆Si₄O₄₆} sites and Lewis acid Cd²⁺/Co²⁺ sites. The conversion of benzaldehyde was up to 99.3% in 80 min at room temperature using 1 as a heterogeneous catalyst with only 0.37% catalyst loading. Moreover, compounds 1–3 as catalysts for selective oxidation of styrene to benzaldehyde exhibited excellent catalytic performance, high selectivity and could be readily recycled. Most strikingly, compound 1 showed excellent catalytic performance with 97.6% conversion of styrene and 100% selectivity of benzaldehyde in 15 min. In addition, the catalytic activity of catalyst 1 was well maintained after five cycling reactions.

Olefin epoxidation represents a crucial transformation in organic synthesis, with significant applications in pharmaceutical and fine chemical industries. Developing efficient catalysts that can utilize molecular oxygen as an environmentally benign oxidant under mild conditions remains a significant challenge. By employing diverse neutral ligands, two novel inorganic-organic hybrid polyoxovanadates were successfully synthesized: [Zn^Ⅱ(cyclam)(H₂O)][V^Ⅴ₈O₁₅(OH)₁₂] (1) and [Zn^Ⅱ(phen)]₂[V^Ⅴ₁₂O₃₂]·H₂O (2) (cyclam=1,4,8,11-tetraazacyclotetradecane, phen=1,10-phenanthroline). These two compounds exhibit unique two-dimensional layered structural characteristics: compound 1 forms a wave-like 2D layer, while compound 2 presents a quasi-planar 2D extended structure. These structural features make the vanadium active centers more accessible to substrates, thereby significantly enhancing catalytic performance. Under optimized conditions, compound 1, using molecular oxygen as the oxidant, achieved a 99.9% conversion rate with 95.4% selectivity for the terminal alkene styrene at 50°C, and a 97.7% conversion rate with over 99% selectivity for the internal alkene cyclooctene at room temperature. Compound 2 also demonstrated similar high catalytic activity. Compared to other catalysts reported in the literature, these two compounds exhibited excellent catalytic performance and stability under mild conditions and could be recycled multiple times without significant loss of activity. Structural analysis revealed that the 2D layered structures of these compounds provide more accessible vanadium active sites, facilitating interactions between substrates and catalysts, thus improving catalytic efficiency.

To control the dimension of the supramolecular system was of great significance. We construct a two component self-assembly system, in which the gelator LHC18 and achiral azobenzene carboxylic acid could co-assembly and form gels. By modulating the stoichiometric ratio of the two components, not only the morphology could be transformed from 1D nanaotube to 0D nanospheres but also the supramolecualr chirality could be tuned. This work could provide some insights to the control of dimension and the supramolecular chirality in the two-component systems by simply modulating the stoichiometric ratio.