Zai-Ming Zhu

A Novel Carboxyethyltin Functionalized Sandwich-type Germanotungstate: Synthesis, Crystal Structure, Photosensitivity, and Application in Dye-Sensitized Solar Cells

A novel sandwich-type germanotungstate [C(NH2)3]10[Mn2{Sn(CH2)2COOH}2(B-α-GeW9O34)2]·8H2O (1) represents the first single crystalline polyoxometalate (POM) functionalized by open chain carboxyethyltin, which was designed and synthesized in aqueous solution and applied to a dye-sensitized solar cell (DSSC) for the first time. Its photosensitivity was explored through a fluorescence spectrum (FL), surface photovoltage spectrum (SPV), electrochemical method, and solid diffuse spectrum. 1 displays the primary features of sensitizers in DSSCs, and the efficiency of the solar cell is 0.22%. Delightedly, when 1 was employed to assemble a cosensitized solar cell configuration by preparing a 1-doped TiO2 electrode and additionally adsorbing N719 dyes, a considerably improved efficiency was achieved through increasing spectral absorption and accelerating electron transport, which is 19.4% higher than that of single N719 sensitization. This result opens up a new way to position different dyes on a single TiO2 film for cosensitization.

Enhanced Visible Photovoltaic Response of TiO2 Thin Film with an All-Inorganic Donor–Acceptor Type Polyoxometalate

In the field of material chemistry, it is of great significance to develop abundant and sustainable materials for solar energy harvesting and management. Herein, after evaluating the energy band characteristics of 13 kinds of polyoxometalates (POMs), the trisubstituted POM compound K6H4[α-SiW9O37Co3(H2O)3]·17H2O (SiW9Co3) was first studied due to its relatively smaller band gap (2.23 eV) and higher lowest unoccupied molecular orbital (LUMO) level (-0.63 V vs NHE). Additionally, the preliminary computational modeling indicated that SiW9Co3 exhibited the donor-acceptor (D-A) structure, in which the cobalt oxygen clusters and tungsten skeletons act as the electron donor and electron acceptor, respectively. By employing SiW9Co3 to modify the TiO2 film, the visible photovoltaic and photocurrent response were both enhanced, and the light-induced photocurrent at 420 nm was improved by 7.1 times. Moreover, the highly dispersive and small sized SiW9Co3 nanoclusters loading on TiO2 were successfully achieved by fabricating the nanocomposite film of {TiO2/SiW9Co3}3 with the layer-by-layer method, which can result in the photovoltaic performance enhancement of dye-sensitized solar cells (DSSCs), of which the overall power conversion efficiency was improved by 25.6% from 6.79% to 8.53% through the synergistic effect of POMs and Ru-complex.

A strategy for breaking the MOF template to obtain small-sized and highly dispersive polyoxometalate clusters loaded on solid films

A strategy was developed for the first time to fabricate highly dispersed and small-sized polyoxometalate nanoparticles loaded on a TiO2 film by using MIL-101 to prevent agglomeration, and calcination to break the metal–organic framework, which can result in performance improvement of quantum dot solar cells.

Two New Armtype Polyoxometalates Grafted on Titanium Dioxide Films: Towards Enhanced Photoelectrochemical Performance.

Two new carboxyethyltin-functionalized polyoxometalates (POMs) were successfully obtained and confirmed with physicochemical and spectroscopic methods including X-ray crystallography. The lowest unoccupied molecular orbitals of both compounds are higher in energy than that of TiO2 , and the optical band gaps of these compounds are smaller than that of TiO2 . Grafting them onto a TiO2 film created two kinds of novel photoanode materials that showed significantly enhanced photovoltaic and photocurrent responses, as well as improved photoelectrooxidation activities for methanol relative to that shown by a single TiO2 film. Further, P2 W15 -Co-SnR produced the largest photocurrent by exploring the photoelectric activities of a series of carboxyethyltin POM derivatives. This work provides new insight into the photoelectrochemical functionalization of POM-based organic-inorganic hybrids.

Two Keggin sandwich-type tungstophosphates modified by open-chain carboxyethyltin groups and transition metals

Two new polyoxometalates containing [PW9O34]9− (abbreviated as PW9) subunits, carboxyltin groups and transition metal ions, namely K10[Mn2{Sn(CH2)2COO}2[(B-α-PW9O34)2]·14H2O (1) and Na8K2 [Zn2{Sn(CH2)2COO}2[(B-α-PW9O34)2]·13H2O (2), were successfully assembled in aqueous solutions by a routine synthetic method, and fully characterized. They represent the first single crystal examples of open-chain carboxyethyltin group-modified Keggin sandwich-type tungstophosphates. Their important structural features are two open-chain carboxyethyltin moieties attached on the PW9 dimer, forming arm-type polyoxometalates. Furthermore, the fluorescence properties, electrocatalytic and oxidation catalytic activities were evaluated. More interestingly, the fluorescence quenching of 1/2-doped TiO2 was clearly observed, which means that the two compounds may be excellent components of photocatalytic materials.

A new boat-like tungstoarsenate functionalized by carboxyethyltin and its catalytic properties

A new polyoxometalate (POM) estertin derivative, {C(NH2)3}Na10K7[(W4O16){Sn(CH2)2COO}4(B-α-AsW9O33)2]·25H2O (1), has been synthesized from K14[As2W19O67(H2O)]·nH2O ({As2W19}) and Cl3SnCH2CH2COOCH3, which exhibits an unusual boat-like structural feature: four [Sn(CH2)2COO]2+ groups surround a center W4O16 cluster and link two [AsW9O33]9− subunits. 1 shows efficient oxidation catalytic activity and can be applied for mimicking enzyme catalysis.

Synthesis, spectroscopic properties and crystal structure of organophosphoryl polyoxotungstate α-[Bu4N]3H[PhCH2P(O)]2SiW11O39

Reaction of the monovacant heteropolyanions α-[SiW11O39]8− with PhCH2PO(OH)2 leads to the formation of the organophosphoryl derivative α-[Bu4N]3H[PhCH2P(O)]2SiW11O39 (1). Single-crystal X-ray diffraction analysis shows that the crystal is monoclinic with space group P21 /n and the unit cell parameters: a = 14.386 (3) Å, b = 27.015 (5) Å, c = 25.480 (5) Å, α = 90°, β = 91.44 (3)°, γ = 90°, V = 9899 (3) Å3. Z = 4, D c = 2.467 g cm−1, λ (Mo-Kα) = 0.071073 nm, R 1 = 0.0638, wR 2 = 0.1364. The hybrid anion consists of an α-[SiW11O39]8− framework on which two equivalent organophosphoryl groups are grafted through P−O−W bridges; each of the two PhCH2P(O) groups are connected to two terminal oxygen atoms belonging to a triad and a diad, respectively.

Hydrothermal syntheses, crystal structures, and thermal stability of two new 3D open-framework metal(II) phosphonates

This article reports the hydrothermal synthesis and characterization of two new phosphonate compounds NaCo[O3PCH(OH)CO2] (1) and NaMn[O3PCH(OH)CO2] (2) based on 2-hydroxyphosphonoacetic acid (H3L). Their structures have been characterized by single-crystal X-ray diffraction as well as with elemental analysis, infrared spectroscopy and thermogravimetric analysis. The two isomorphous compounds crystalline in the orthorhombic, space group Pbca: Crystal data for 1: a = 10.1827(8) Å, b = 9.6673(8) Å, c = 10.7853(9) Å, V = 1061.70(15) Å3, Z = 8, R 1 = 0.0252, wR 2 = 0.0577; Crystal data for 2: a = 10.4309(18) Å, b = 9.7913(17) Å, c = 10.9012(19) Å, V = 1113.4(3) Å3, Z = 8, R 1 = 0.0194, wR 2 = 0.0536. In the two compounds, the metal atoms are octahedrally coordinated; all oxygen atoms from the H3L ligand are involved in coordination. The overall structures can be described as a 3D open framework with channels running along the a axis and the charge-compensating Na+ cations being located at the intersections of these channels.

Synthesis and characterization of organophosphoryl polyoxotungstates [RP(O)]2Xn+W11O39(8−n)− (Xn+ = P5+, Si4+, Ge4+, Ga3+)

In the presence of n-Bu4NBr acting as phase-transfer reagent, n-Bu4N+ salts of organophosphoryl polyoxotungstate derivatives [RP(O)]2Xn+W11O39(8−n)− [R = PhCH2CH2P(O), X = P, Si; R = C6H11P(O); X = Ge, Ga] have been prepared and characterized by elemental analysis, i.r., 31P- and 183W-n.m.r. spectroscopy. According to the elemental analysis and spectroscopic data, the hybrid anions consist of an α-[XW11O39] framework on which are grafted two equivalent organophosphoryl groups through P—O—W bridges; these new species still retain the Keggin structure. The six-line 183W spectrum indicates that hybrid anions possess Cs symmetry in MeCN.

Extended visible photosensitivity of carboxyethyltin functionalized polyoxometalates with common organic dyes enabling enhanced photoelectric performance

A kind of broad spectral responsive photoelectrode has been assembled from open-chain carboxyethyltin functionalized Dawson sandwich-type polyoxometalates (POMs) [{Sn(CH2)2COO}2M2(P2W15O56)2]16− (SnR-M-P2W15, M = Mn, Co, Cu and Zn) and organic dyes such as rhodamine B (RhB) and methylene blue (MB) through the layer-by-layer (LBL) self-assembly method. SnR-M-P2W15 shows strong adsorption towards RhB and MB. The adsorption capacity of SnR-Co-P2W15 towards RhB and MB reached 217.36 and 288.76 mg g−1 in 10 min, respectively. Compared to Keggin sandwich-type open-chain carboxyethyltin–POM and closed-ring carboxyethyltin–POM derivatives such as [Zn2{Sn(CH2)2COO}2[(PW9O34)2]10− (SnR-Zn-PW9) and [K3{Sn(CH2)2COO}2(PW9O34)2]11− (SnR-PW9), and the parent POMs [M4(H2O)2(P2W15O56)2]16− (M-P2W15, M = Mn, Co, Cu and Zn), SnR-M-P2W15-based photoelectrodes showed significantly enhanced photocurrent owing to their greater visible light harvesting. Also, the photoelectric performances of LBL multilayer films can be adjusted by controlling the number of deposited layers, adsorbed dye types and incorporated transition metal ions in the POMs.