Molecular solid solution of lanthanide-titanium-oxo clusters with enhanced photocatalytic hydrogen evolution

Molecular solid solutions of metal clusters containing different metal centers with well-defined structures can accurately regulate the HOMO-LUMO gap,but are rarely available.Herein,a series of colorless lanthanide-titanium-oxo clusters Ln_(2)Ti_4(μ_(2)-O)_(2)(μ_(3)-O)_4(Piv)_(10)(THF)_(2)(Ln_(2)Ti_4,Ln = Eu,Gd,Tb,and Ce,HPiv = pivalic acid) were synthesized by the reaction of pivalic acid with Ln(Ac)_(3) and titanium isopropoxide.The light yellow crystal of cluster solid solutions Eu_(2)Ti_(4-x)Cd_(x),containing a mixture of Eu_(2)Ti_4 and Eu_(2)Ti_(3)Cd,was obtained by in situ doping Cd^(2+) and S^(2–).Eu_(2)Ti_(3.92)Cd_(0.08) displays efficient photocatalytic hydrogen evolution activity without a co-catalyst,which is up to 2.6 times that of Eu_(2)Ti_4.Femtosecond time-resolved transient absorption spectroscopy and spin-polarized density functional calculations showed that the enhanced photocatalytic performance of Eu_(2)Ti_(4-x)Cd_(x) can be attributed to the narrower HOMO-LUMO gap and lower LUMO position than that of Eu_(2)Ti_4.This studyprovides an in situ doping method to realize the simple preparation of cluster solid solution.

Anchoring heterometallic cluster on P-doped carbon nitride for efficient photocatalytic nitrogen fixation in water and air ambient

Light-driven nitrogen fixation to produce ammonia is a green and economical technology of nitrogen reduction but is still quite challenging, especially in an air atmosphere without any sacrificial reagents.Herein, we demonstrate efficient photocatalytic nitrogen fixation using water and air directly by loading lanthanide–transition metal(4f–3d) cluster NdCo_(3) on two-dimensional P-doped graphitic carbon nitrides(PCN) material surface. Benefiting from the increase in the number of nitrogen vacancies(NVs) and highly matched band gap structure and excellent hole trapping ability of clusters, the NdCo_(3)/PCN photocatalyst exhibits efficient nitrogen reduction activity with 371(in air) and 825 μmol h^(-1)g^(-1)(in pure nitrogen)without any sacrificial reagents. The introduction of potassium sulfate inhibits hydrogen production and promotes nitrogen reduction activation. This work suggests that anchoring precisely structured clusters on 2D materials may enhance photocatalytic nitrogen reduction under normal temperature and pressure.

基于电荷转移的分子基铁电和磁电材料

电荷转移行为在分子基材料的自旋双稳态、价态互变等诸多体系中一直发挥着关键作用,基于分子基化合物中电荷转移构筑铁电和磁电材料是近年来新发展的研究方向,并吸引化学、材料及物理研究者们的广泛关注.相对于传统的铁电和磁电材料发生机制,电荷转移引发或诱导的分子铁电和磁电材料,在加快器件运行速度的同时,可以实现局域磁矩的调控,因而通过外场调控有望实现磁电耦合.本文就基于电荷转移引发或诱导的分子基铁电和磁电材料研究体系进行分类,并进行系统性论述.此外,还提出个人观点,对当前领域的发展前景进行展望,希望能够为相关领域的研究者提供一些启示或参考.

Synthesis,structures and photoluminescence of uranyl polyoxometalate clusters based on trilacunary[TeW_(9)O_(33)]^(8-)

Synthesis of uranyl polyoxometalate clusters attract more attention but remain great challenging.Herein,two uranyl polyoxometalate inorganic clusters of{Na_(6)(NH_(4))_(19)[(TeW_(9)O_(33))_(4)[TeO_(2)(OH)](UO_(2))4(H_(2)O)_(2)]·50H_(2)O}n(1,Te-U_(4))and(NH_(4))18{Na@[(TeW_(9)O_(32)OH)(TeW_(9)O_(33))_(2)[TeO(OH)][W_(3)O_(12)(μ_(3)-OH)](UO_(2))_(6)(μ_(2)-OH)_(2)H_(2)O]}·75H_(2)O(2,Te-U6)were prepared using trilacunary[α-B-TeW_(9)O_(33)]8-as inorganic ligands.Structural analysis showed that compound 1 is a one-dimensional chain structure formed by tetrameric aggregates of[(α-B-TeW_(9)O_(33))_(4)(TeO_(2)(OH))(UO_(2))_(4)(H_(2)O)2]25-as nodes and Na+ions as linkers.The anionic tetrameric aggregates in 1 is made of two sandwich-type dimers of[(TeW_(9)O_(33))_(2)(UO_(2))_(2)H_(2)O]12-bridged by a[TeO_(2)(OH)]-unit.Compound 2 is a triangular trimeric architecture templated by Na+ion.The solid-state luminescence emission spectra of compounds 1 and 2 show the characteristic peaks of uranyl ions.Compound 1 with one-dimensional chain structure exhibited a higher photoluminescence quantum yields(PLQY)than that of 2,due to the more rigidity of 1 reducing the nonradiative transitions.

Lanthanide-oxo clusters for efficient catalytic reduction of carboxamides

The reduction of carboxamides into high value-added amines is a very interesting but great challenging topic.Herein we demonstrate that polynuclear lanthanide-oxo clusters Ln16(Ln=Eu and Gd)can be used as efficient catalyst to reduce primary and secondary carboxamides to amines with excellent yield of 71%-98%and broad substrates scope.The methodology can extend to the gram-scale synthesis of phenethylamine drug with 93%yield.Based on the isolation and characterization of catalytic intermediates,a catalytic mechanism involving multipath reaction is proposed.This work provides efficient lanthanide cluster catalysts for the reduction of carboxamides to amines.

Highly stable Eu-coordination polymer exhibiting the highest quantum yield

Lanthanide luminescent materials with high quantum yield and thermal stability are of key importance for their practical application.Here we report crystal structures and luminescent properties of[Eu(pfbz)_(2)(phen)Cl](1)and[Tb(pfbz)2(phen)Cl](2)(pfbz=Pentafluorobenzoate).Single-crystal analysis reveals that both 1 and 2 crystallize in a polar space group of Cmc21.Investigation on their luminescent properties indicates that the solid-state quantum yields of 1 and 2 are 97.7%and 90.7%,respectively,while their efficiency of the sensitization process is as high as 100%,revealing that polar structures are more favorable to obtain high quantum yields.Thermogravimetric analysis reveals that both 1 and 2 can be stable up to 240℃.More importantly,temperature-dependent luminescent spectra of 1 indicate its luminescent intensity at 612 nm only decreased by 5%from room temperature to 373 K,whereas at 373 K,its luminescent intensity remains almost constant for 36 h.Considering that1 represents the highest quantum yield among known Eu-coordination polymers and its performance as the LED material is better than that of commercially widely used luminescent materials of(Sr,Ca)Al Si N3:Eu(630 nm)and(Sr,Ca)Al Si N3:Eu(640 nm),the present work provides an excellent substitute for commercial LED materials.

Encapsulating a Ni（Ⅱ） molecular catalyst in photoactive metal–organic framework for highly efficient photoreduction of CO2

Photocatalytic reduction of CO2 to CO is a promising strategy for reducing atmospheric CO2 levels and storing solar radiation as chemical energy.Here,we demonstrate that a molecular catalyst[NiⅡ(bpet)(H2O)2]successfully encapsulated into a highly robust and visible-light responsive metal–organic framework(Ru-UiO-67)to fabricate composite catalysts for photocatalytic CO2 reduction.The composite Ni@Ru-UiO-67 photocatalysts show efficient visible-light-driven CO2 reduction to CO with a TON of 581 and a selectivity of 99% after 20-h illumination,because of the facile electron transfer from Ru-photosensitizer to Ni(Ⅱ)active sites in Ni@Ru-UiO-67 system.The mechanistic insights into photoreduction of CO2 have been studied based on thermodynamical,electrochemical,and spectroscopic investigation,together with density functional theory(DFT)calculations.This work shows that encapsulating molecular catalyst into photoactive MOF highlights opportunities for designing efficient,stable and recyclable photocatalysts.

Enhanced proton conductivity of Mo_(154)-based porous inorganic framework

The construction of inorganic porous frameworks from discrete polyoxometalate(POM)units is a major research challenge.Herein,a three-dimensional(3D)all-inorganic porous structure{Mo_(154)}_n that consists of classic Mo_(154)rings connected by Mo–O–Mo covalent bonds was synthesized.Interestingly,the proton conductivity of the 3D-{Mo_(154)}_n framework is 1.1×10^(-2)S cm^(-1)at 22℃and 100%relative humidity(RH),which is one of the highest proton conductivities reported thus far for POM-based conductive materials.Compared to the discrete{Mo_(154)}cluster and 1D-{Mo_(154)}_n,the enhanced conductivity of 3D-{Mo_(154)}_n suggests that assembling POM-based all-inorganic porous frameworks is a promising method for designing proton-conductive materials.