A highly reduced Mo_(74) polyoxometalate featuring high proton conductivity accessed by building block strategy

Highly reduced polyoxometalates(POMs) are predicted to be used as rather high energy density materials;however,it still suffers from the limited cluster species and reduction ratio.Here we demonstrate that it is possible to employ the building block strategy to generate a highly reduced polyoxomolybdate(C_(2)H_(8)N)_(14)(NH_(4))_(4)H_(14)[Mo_(48)-ⅤMo_(26)ⅥO_(202)(OH)_(12)(SO_(4))_(6)]·46H_(2)O(Mo_(74)).The fundamental Mo-based{Mo_x}(x=4,5,and 6) building blocks,which are templated by tetra-coordinated anions{MoO_(4)}or{SO_(4)},not only lay foundation for the formation of Mo_(74) featuring an unprecedented reduction ratio of 65%,but also give rise to SBBs-mediated(secondary building blocks) supramolecular dense packing interactions among the isolated Mo_(74) clusters that are favorable for proton conduction.Remarkably,high proton conductivity(2.04×10^(-2)S cm^(-1)) had been realized at 50℃ and 90% relative humidity,revealing one of the well-known POMs-based crystalline proton conducting materials.This result highlights that this building block approach possesses great potential in producing highly reduced POM systems that can achieve controllable reduced ratio and desirable properties.

Evolution exploration and structure prediction of Keggin-type group IVB metal-oxo clusters

The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates(POMs)have attracted many chemists to explore and discover continuously.Unlike the traditional Keggin,larger metal atomic radius,higher metal coordinated numbers,lower metal valence states and other features allow the group IVB metal-based Keggin(IVB-Keggin)more space and unknown in terms of structure and performance.Herein,density functional theory(DFT)calculations were performed to explore the influences including cores,shells,caps,and terminal ligands,et al.on IVB-Keggin,and analyze the possibility of novel structure synthesis.From the perspective of multi-layer onion-like clusters,molecular energy level,host-guest interaction energy,surface charge and covalent bond polarity can be further adjusted to achieve the oriented design of functional IVB-Keggin.These insights are expected to provide theoretical support for experimental synthesis,opening a new perspective to understand the growth of Keggin.

Organophosphate functionalized of {Mo_(240)} polyoxomolybdate dodecahedra

Two organophosphate-functionalized hybrid polyoxomolybdates dodecahedra(NH_(4))_(21)H^(+)59[MoⅤ_(180)Mo^(Ⅵ)60(OH)_(60)O_(620)(C_(6)H_(5)PO_(3))_(20)]·260H_(2)O(1)and(NH_(4))_(21)H^(+)59[Mo^(Ⅴ)180Mo^(Ⅵ)60(OH)_(60)O_(620)(NC_(5)H_(4)PO_(3))_(20)]·260H_(2)O(2)are constructed under hydrothermal conditions.In both structures,20 phenylphosphonic acids or pyridyl-4-phosphonic acids are simultaneously grafted onto the interior of the{Mo_(240)}dodecahedral cage,forming an organic-inorganic polyoxomolybdate hybrids.The introduction of more strongly coordinated phenylphosphonic and pyridyl-4-phosphonic acid within the inner surface of{Mo_(240)}altered the microenvironment within the cage.Both structures exhibit good water and thermal stabilities.Furthermore,crystals 1 and 2 were selected for adsorption of cationic dyes with the same charge and different sizes,which showed significant scavenging effect on the large size of cationic dyes.This study provides a new perspective on the functionalization of polyoxometalate cages.

Microenvironment Modulation of Imine-Based Covalent Organic Frameworks for CO_(2) Photoreduction

Photocatalytic CO_(2) reduction to fuels and chemicals has been considered as the promising avenue to realize carbon resource recycling.Covalent organic frameworks(COFs)with pre-designed and tailorable structures are promising platforms for studying the influence of the microenvironment of catalysts on photocatalytic CO_(2) reduction.Herein,we report three isomorphic COFs(TPHH-COF,TPPD-COF and TPBD-COF)as heterogeneous photocatalysts for CO_(2) reduction and investigate the different levels of conjugation and planarity of COFs effect on the catalytic activity.Photoelectrochemical measurements show that TPPD-COF has a narrower band gap and faster photocurrent response compared to TPHH-COF and TPBD-COF,probably due to the moderate conjugation and planarity.As the photocatalyst,TPPD-COF showed the most outstanding photocatalytic activity with the production rates of 951 and 157μmol·g^(–1)·h^(–1) for CO and H2,respectively.This study illustrates the close relation between microenvironment and photocatalytic activity and provides new insights for designing high-performance.

Radical Mechanism of IrⅢ/NiⅡ Metallaphotoredox-Catalyzed C(sp^(3))-H Functionalization Triggered by Proton-Coupled Electron Transfer:Theoretical Insight

Photoredox catalysis can be induced to activate organic substrates or to modulate the oxidation state of transition-metal catalysts via unique singleelectron transfer processes,so as to achieve challenging C(sp^(3))-H functionalization under mild conditions.However,the specific reaction mechanism and relevant electron transfer process still need to be clarified.Here,a highly regioselective Ir^(Ⅲ)/Ni^(Ⅱ)-metallaphotoredox-catalyzed hydroalkylation of asymmetrical internal alkyne with an etherα-hetero C(sp^(3))-H bond has been investigated by density functional theory(DFT)calculations.A novel radical mechanism was predicted to merge oxidative quenching(Ir^(Ⅲ)-*Ir^(Ⅲ)-Ir^(Ⅳ)-Ir^(Ⅲ))and nickel catalytic cycles(NiⅡ-NiⅢ-NiI-NiⅢ-NiⅡ)for this C(sp^(3))-H functionalization to construct C(sp^(3))-C(sp^(2))bonds.It consists of seven major steps:the single-electron transfer involved in the photoredox cycle for generating active Ni(Ⅰ)-chloride complexes,proton-coupled electron transfer process to provide α-carbon-centered tetrahydrofuran(THF)radicals,radical capture by Ni(Ⅱ),reductive elimination to obtain 2-chlorotetrahydrofuran,alkyne oxidative hydrometallation,innersphere electron transfer,and σ-bond metathesis to yield the desired alkyne hydroalkylation product.Importantly,both the thermodynamic performance for redox potentials and the kinetic exploration for energy barriers and electron-transfer rates have also been evaluated for the corresponding electron transfer processes.In addition,the steric effects play a major role in determining the regioselectivity of alkyne oxidative hydrometallation.