High-performance piezoelectric materials are desirable for piezoelectric sensing applications. In this paper, piezoelectric α-BiB3O6 (BIBO) crystals were explored for high temperature sensing. Dielectric, piezoelectric and electromechanical properties were evaluated by using the impedance method, from which the piezoelectric charge coefficients were determined to be d14 = 10.9, d16 = 13.9, d21 = 16.7, d22 = 40.0, d23 = 2.5, d25 = 4.3, d34 = 18.7 and d36 = 13.0 pC/N, with corresponding piezoelectric voltage coefficients g14 = 122, g16 = 144, g21 = 225, g22 = 538, g23 = 34, g25 = 58, g34 = 165 and g36 = 121 × 10−3 V m N−1 at room temperature (RT). Of particular significance is that the receiving sensitivity of BIBO crystals was found to be 47.2 pm2 N−1, nearly one order of magnitude higher than that of LiNbO3 crystals. Moreover, the BIBO crystals were found to possess a high mechanical quality factor Qm (13000 at RT and >1000 at 600 °C), low dielectric loss (<0.1% at RT and 15% at 600 °C and 1 kHz), high electrical resistivity (∼2.5 × 108 Ω cm at 600 °C) and high temperature stability of piezoelectric coefficients (variations <±10%). All these properties demonstrate that BIBO crystals are promising for piezoelectric sensing over a broad temperature range.

New rare-earth calcium oxyborate crystals TmCa4O(BO3)3 (TmCOB) were grown by using the Czochralski pulling method, and the mechanical and thermal properties were investigated. In addition, the dielectric, elastic and piezoelectric performance was evaluated by impedance measurement, where the piezoelectric charge coefficients were determined to be on the order of d11 = 1.7, d12 = 3.8, d13 = −4.2, d15 = −0.92, d24 = 4.9, d26 = 7.8, d31 = −0.75, d32 = −2.4, d33 = 2.2 and d35 = −5.2 pC N−1. The temperature-dependent electrical resistivity and electro-elastic properties were studied from room temperature to 900 °C, where a high electrical resistivity of ~6 × 107 Ω cm and a low dielectric loss of ~21% were achieved at 900 °C, with high thermal stability of electromechanical coupling factors and piezoelectric coefficients over the temperature range of 20–900 °C. All of these properties demonstrate that TmCOB crystals are an attractive candidate for high-temperature sensor fabrications.

Four new coordination polymers, namely [Co(H2O2abtc)(bibp)]n (1), {[Mn1.5(Oabtc)(H2O)2]·(H2bmib)0.5·H2O}n (2), {[Cd1.5(O2abtc)]·(H2bmib)0.5·2H2O}n (3), and {[Cd(nip)(bibp)]·0.5H2O}n (4),were constructed under solvothermal conditions in the presence of two bis(imidazole) bridging linkers (bimb = 1,4-bis(2-methylimidazol-1-ylmethyl)benzene, bibp = 4,4′-bis(imidazol-1-yl)biphenyl). The unstable azo ligand of 3,3′,5,5′-azobenzenetetracarboxylic acid (H4abtc) could be oxidized and resulted in three oxidized derivatives of H4Oabtc (one N atom was oxidized), H4O2abtc (two N atoms were oxidized), and H2nip (one H4abtc was oxidized to two 5-nitroisophthalic acids). Their structures were determined by single-crystal X-ray diffraction and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Complex 1 exhibited an interestingly 2D + 2D → 3D parallel entangled network based on 4-connected (44·62)-sql sheets. Complex 2 was found to be a {Mn3(COO)6} trinuclear SBU based 2D (3,6)-connected (43)2(46·66·83)-kgd sheet. While complex 3 displays a {Cd3(COO)8} trinuclear SBUs based 3D (4,8)-connected (46)2(412·612·84)-flu network. Complex 4 can be regard as a {Cd2(COO)2} binuclear SBUs based 6-connected (44·611)-6T8 framework. In addition, the magnetic property of complexes 1, 2 and the luminescence properties of complexes 3, 4 were investigated.

Four mixed-ligand coordination networks, namely, {[Cu(pta)(1,4-bimb)0.5(H2O)0.5]·H2O}n (1), {[Co(pta) (4,4′-bimbp) (H2O)]·H2O}n (2),{[Cd(pta)(1,4-bidb)0.5]·2H2O}n (3), and {[Zn(pta)(1,3-bimb)0.5]·1.5H2O}n (4), were obtained under the solvothermal reactions in the presence of bis(imidazole) linkers (H2pta = 6-(4-pyridyl)-terephthalic acid, 1,4-bidb = 1,4-bis(imidazol-1-yl)-2,5-dimethyl benzene, 1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, 1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, and 4,4′-bimbp = 4,4′-bis(imidazol-1-ylmethyl)biphenyl). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complex 1 displays a novel (3,4,4)-connected topology with the Schläfli symbol of (4.82)2(42.82.102)(8.104.12). Complex 2 features a 2D (3,5)-connected (42.67.8)(42.6)-3,5L2 sheet. Complexes 3 and 4 both exhibit a 3-fold 3D → 3D parallel entangled (3,4)-connected net with the Schläfli symbols of (4.6.8)(4.62.63)-fsc-3,4-C2/c and (4.6.8)(4.62.83)-3,4T1 for 3 and 4, respectively. Moreover, the solid state luminescence and the luminescent lifetime of 3 and 4 have been investigated.

Four new coordination polymers (CPs), {[H2N(CH3)2]2[Ln2(BPT)(ox)2]}n (Ln = Er for 1, Yb for 2, and Sm for 3; H2ox = oxalic acid) and {[Gd(HDCP)(H2O)]·H2O}n (4), have been constructed from Ln ions and two aromatic tetracarboxylate acids (H4BPT = 3,3′,5,5′-biphenyltetracarboxylic acid, H4DPT = 4,5-di(4′-carboxylphenyl)phthalic acid) under solvothermal reactions through the linker extension strategy. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Complexes 1–3 are isomorphous and exhibit an unprecedented (6,8)-connected 3D architecture with a point symbol of (33·410·57·62·76)(33·46·56)2, which is built up from right- and left-handed [Ln(ox)]n helixes. Complex 4 shows a 3D (4,8)-connected flu net with (412·612·84)(46)2 topology based on 1D [Gd(COO)2]n ladder chains. Moreover, their luminescence properties have been investigated.

A series of 2D and 3D transition coordination polymers (CPs), {[M(bcpb)(1,4-bmib)0.5]·xH2O}n (M = Co (1), Cu (2), Ni (3), x = 1 for 1, 0 for 2 and 3), {[Co(bcpb)(4,4′-bibp)0.5(H2O)1.5]·1.5H2O}n (4), [Cu(bcpb)(4,4′-bibp)0.5(H2O)]n (5), {[Ni(bcpb)(4,4′-bimbp)(H2O)]·2.5H2O}n (6), [Co(bcpb)(4,4′-bimbp)]n (7), [Mn(pip)(MeOH)(H2O)]n (8), {[Ni(pip)(4,4′-bibp)0.5(H2O)]·2H2O}n (9), and {[Cu(pip)(4,4′-bimbp)]·4H2O}n (10), were synthesized under hydrothermal conditions in the presence of two trifunctional pyridinedicarboxylates and different (bis)imidazole bridging linkers (H2bcpb = 3,5-bis(4-carboxyphenyl)pyridine, H2pip = 5-(4-pyridyl)isophthalic acid, 1,4-bmib = 1,4-bis(2-methylimidazol-1-ylmethyl)benzene), 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl, 4,4′-bimbp = 4,4′-bis(imidazol-1-ylmethyl)biphenyl). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Single crystal X-ray diffraction analyses reveal that complexes 1–3 are isomorphic and show complicated 3D (3,5)-coordinated amd networks, which could be viewed as two interpenetrated ths nets. Complex 4 is a binodal (3,4)-connected 3D framework with the Schläfli symbol of (4·72)(4·75·84). Complex 5 exhibits an intriguing 3D 2-fold interpenetrated network with the (3,4)-connected dmc net. Complex 6 is a 2D (3,5)-connected gek1 net with right- and left-handed [Ni(4,4′-bibp)]n helical chains arranged alternately. The 3D framework of 7 is defined as a 2-fold interpenetrated (3,5)-connected gra topology. Complex 8 displays a 2D 3-connected 63-hcb network. Complex 9 can be regarded as a (3,4)-coordinated crs-d network with a point symbol of (62·8)(63·8·102), which contains two interpenetrated 3-coordinated 103srs subnets linked by 2-coordinated 4,4′-bibp. Complex 10 is a binodal (3,5)-connected 3D framework with point Schläfli symbol of (4·6·8)(4·64·85). To the best of our knowledge, the 3D CPs with (3,4)-connected (4·72)(4·75·84) for 4, and (3,5)-connected (4·6·8)(4·64·85) for 10 have never been documented up to now. Moreover, the magnetic properties of 4 have been investigated.

The solvothermal reactions of terphenyl-2,5,2′,5′-tetracarboxylic acid (H4tptc) and transition metal cations (NiII, MnII) afford five novel coordination polymers (CPs) in the presence of four bis(imidazole) bridging ligands (1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, 1,4-bmib = 1,4-bis(2-methylimidazol-1-ylmethyl)benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl, 4,4′-bimbp = 4,4′-bis(imidazol-1-ylmethyl)biphenyl), namely, [M(tptc)0.5(1,3-bimb)(H2O)]n (M = Ni for 1, Mn for 2), {[Ni(tptc)0.5(1,4-bmib)]·0.25H2O}n (3), {[Ni(tptc)0.5(4,4′-bibp)2(H2O)]·2H2O}n (4) and {[Ni(tptc)0.5(4,4′-bimbp)1.5(H2O)]·H2O}n (5). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complexes 1 and 2 are isomorphous and exhibit a 3D (3,4)-connected tfi framework with the point Schläfli symbol of (4·62)(4·66·83). Complex 3 shows an unprecedented 3D (4,4)-connected framework with the point Schläfli symbol of (4·64·82)2(42·84). Complex 4 displays a novel 2D self-catenating 5-connected network with the Schläfli symbol of (46·64) based on three interpenetrating 44-sql subnets. Complex 5 features a 2D 3-connected 63-hcb network built from interesting chains with loops. To the best of our knowledge, the 3D (4,4)-connected (4·64·82)2(42·84) host-framework of 3 and 2D self-catenating 5-connected (46·64) network of 4 have never been documented to date. Moreover, the UV-Visible absorption spectra of complexes 1–5 have been investigated.

Five coordination polymers (CPs), namely {[Ni1.5(BPT)(1,4-bib)2(H2O)]·(1,4-bib)0.5·2H2O}n (1), {[Co2(BPT)(1,3-bimb)(μ3-OH)]·H2O}n (2), {[Zn(HBPT)(1,3-bimb)]·H2O}n (3), {[Co2(BPT)(H2BPT)(4,4′-bibp)2]·2H2O}n (4), and [Mn2.5(BPT)(4,4′-bibp)2.5(SO4)(H2O)]n (5) (H3BPT = biphenyl-3,4′,5-tricarboxylic acid, 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene, 1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, and 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl), were synthesized under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complex 1 exhibits unprecedented 2D + 2D → 3D parallel entangled networks consisting of trilayer (3,4,6)-connected (44·54·66·8)(5·64·8)2(52·62) sheets. Complex 2 displays a 3D (3,10)-connected 3,10T9 net based on tetranuclear {Co4(μ3-OH)2} clusters with the Schläfli symbol (418·624·83)(43)2. Complex 3 shows an interesting 1D tube-like chain consisting of Zn2(1,3-bimb)2 loops. Complex 4 affords a 2D (44·62)-sql net constructed from {Co2} dinuclear units. Complex 5 displays a 3D 6-connected (412·63)-pcu net consisting of α-Po primitive cubic nets based on {Mn5(SO4)2} clusters. Moreover, magnetic studies indicate that complexes 2, 4 and 5 show antiferromagnetic properties.

Solvothermal reactions of the semirigid 3,5-bi(4-carboxyphenoxy)benzoic acid (H3BCP) and transitional metal cations with the help of three ancillary bridging imidazole linkers afforded six coordination polymers, namely, [Co(HBCP)(1,4-bib)0.5]n (1), {[Mn1.5(BCP)(1,4-bib)0.5(μ2-H2O)(H2O)2]·(1,4-bib)0.5}n (2), {[Mn0.5(1,4-bib)(H2O)]·(H2BCP)}n (3), {[Fe(BCP)0.5(HCOO)0.5(4,4′-bibp)0.5]·2H2O}n (4), [Ni2.5(HBCP)(BCP)(4,4′-bibp)2(μ2-H2O)(H2O)2]n (5), and [Ni(HBCP)(1,4-bidb)1.5(H2O)2]n (6), (1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene, 1,4-bidb = 1,4-bis(1-imidazol-yl)-2,5-dimethyl benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl). Their structures and properties were determined by single-crystal and powder X-ray diffraction analyses, IR spectra, elemental analyses, thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS). Complex 1 displays unusual 2D + 2D→2D parallel entangled networks consisting of (3,4)-connected 3,4L83 sheets. Complex 2 exhibits an interesting 2-fold interpenetrated framework with a trinodal (4,4,6)-connected (3·4·5·62·7)2(3·6·74)2(32·42·52·62·76·9) topology. The host network of complex 3 is a 2D 4-connected (44·62)-sql sheet. Complex 4 affords unprecedented 3D (4,6,6)-coordinated framework with point symbol of (45·6)(48·67)(49·63·83)2, in which the 1D helix water chains occupy the void channels. Complex 5 can be regarded as a novel self-penetrating (4,4,4,5)-coordinated framework with point symbol of (4·54·6)2(4·65·7·83)2(5·6·7·83)2(52·83·92), which contains two interpenetrated (3,4,4,5)-coordinated (4·54·6)2(4·65·7·83)2(5·6·7)2(52·83·92) subnets linked by μ2-H2O. Complex 6 shows a 1D ladder chain, which are further assembled into a 3D supramolecular structure via O–H⋯O and π⋯π interactions. Moreover, magnetic studies indicate that both complex 2 and 4 show antiferromagnetic properties.

Six 4,5-di(4′-carboxylphenyl)phthalic acid (H4DCP) based coordination polymers (CPs), namely {[Ni(1,4-bib)(HDCP)2(H2O)2]0.5[Ni(1,4-bib)(H2O)4]·2H2O}n (1), [Ni(H2DCP)(1,4-bidb)2(H2O)]n (2), [Co2(DCP)(1,3-bib)]n (3), {[Co2(DCP)(1,4-bidb)2]·2H2O}n (4), [Co(H2DCP)(4,4′-bibp)]n (5), and [Co2(DCP)(4,4′-bibp)2]n (6), were synthesized under hydrothermal conditions in the presence of bis(imidazole) bridging linkers (1,3-bib = 1,3-bis(imidazol-1-yl)benzene, 1,4-bib = 1,4-bis(imidazol-1-yl)benzene, 1,4-bidb = 1,4-bis(imidazol-1-yl)-2,5-dimethyl benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl). Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Single crystal X-ray diffraction analysis reveals that complex 1 is a cocrystal consisting of two independent chains. Complex 2 exhibits a traditional 2-fold 66-dia parallel entangled network. Complex 3 displays a novel 3D binodal (5,7)-connected net based on binuclear {Co2} units with the Schläfli symbol (3·44·54·6)(32·48·58·63). Complex 4 shows a 2-fold binodal (4,4)-connected bbf net with the point symbol (64·86)(66)2. Complex 5 affords a 2D (44·62)-sql net constructed from {Co2} dinuclear units. Complex 6 displays a novel (3,8)-connected architecture with the Schläfli point symbol (42·5)2(44·510·68·74·82) based on {Co4(COO)6} SBUs. Magnetic studies indicate complexes 3 and 6 exhibit weak ferromagnetic and antiferromagnetic properties, respectively.

Solvothermal reactions of one semirigid tricarboxylic acid and transition metal cations in the absence or presence of 1,4-bis(1H-imidazol-4-yl)benzene (1,4-bib) afford four coordination polymers, namely, [Cd(Hbcb)]n (1), and [M(Hbcb)(1,4-bib)]n (M = Cd (2), Mn (3), Fe (4)) (H3bcb = 3,5-bis((4′-carboxylbenzyl)oxy)benzoic acid). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Structural analysis revealed that complex 1 exhibits an intriguing [Cd(COO)2]n tube-like chain based 3D framework with unprecedented 6-connected (48·67) topology. Complexes 2–4 show isomorphism and show new 3D (3,5)-connected frameworks with the point Schläfli symbol of (4·6·8)(4·64·85) based on the [M(COO)]n chain. Moreover, the photoluminescence properties of 1 and 2 have been investigated in the solid state at room temperature.

A novel-type 3D polyoxomolybdate–organic framework, {[Cu3(H3tpb)2(tpb)(Mo4O12)]·4H2O}n (1, H3tpb = 1,3,5-tri(1H-pyrazol-3-yl)benzene), was prepared and characterized by elemental analysis, IR spectroscopy, and luminescence analysis. Single-crystal X-ray diffraction analysis reveals that novel neutral triple helix {Mo4O12}n chains are encased in bowl-like 2D [Cu3(H3tpb)2(tpb)]n intervals via bond interactions between terminal oxygen atoms and cations of Cu(I), leaving an unprecedented (3,3,5,8)-connected (3·4·68)3(36·46·86·96·104)(43)2(63) topology. Moreover, compound 1 exhibits remarkable photocatalytic activities for decomposition of methylene orange (MO), methylene red (MR), methylene blue (MB), methylene violet (MV), and rhodamine B (RhB) under UV light.

A series of novel multidimensional transition metal–organic frameworks (MOFs), [Cu(Hbcpb)2]n (1), [Co(bcpb)]n (2), [Co(Hbcpb)2(1,4-bib)]n (3), {[M(bcpb)(1,4-bimb)]·xH2O}n (M = Co (4), Cu (5), Ni (6), x = 1 for 5, 2 for 4 and 6), [Co(bcpb)(4,4′-bibp)]n (7), {[Co(bcpb)(4,4′-bibp)]·2H2O}n (8), and [Ni2(bcpb)2(4,4′-bimbp)2]n (9), were synthesized under hydrothermal conditions in the presence of N-donor ancillary ligands [H2bcpb = 3,5-bis(3-carboxyphenyl)pyridine, 1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene, 1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl, 4,4′-bimbp = 4,4′-bis(imidazol-1-ylmethyl)biphenyl]. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. By adjusting the reaction pH, the H2bcpb ligand is partially deprotonated to give the Hbcpb– form in 1 and 3, and completely deprotonated to afford the bcpb2– form in 2 and 4–9. Complex 1 exhibits a two-dimensional (2D) (3,6)-connected kgd topology with the Schläfli symbol of (43)2(46·66·83). The three-dimensional (3D) framework of 2 is defined as a (4,4)-connected pts topology with the Schläfli symbol of (42·84). Complex 3 displays a (4,6)-connected pcu topology with the Schläfli symbol of (412·63) built from 44 2D nets with the help of 1,4-bib. Complexes 4–6 are isomorphism and show a 3D (3,5)-connected mbm framework with the Point Schläfli symbol of (4·62)(4·66·83). The supramolecular isomers of 7 and 8, resulted from the different pH in the reaction, exhibit (3,5)-connected (42·67·8)(42·6) 3,5-L2 and (4,6)-connected (44·610·8)(44·62) fsc topology, respectively. Complex 9 can be regard as an unprecedented (3,5)-connected 3D 3,5-T1 frameworks with the point Schläfli symbol of (42·65·83)(42·6). The results revealed that the crystal architectures and the coordination modes of H2bcpb are attributed to the factors, including metal cations, pH, and the N-donor ancillary ligands.

Solvothermal reactions of two trigonal-planar ligands and lanthanide metal cations of LnIII afford four new coordination polymers (CPs), {[LnNa0.33H0.67(PBPP)2]·2H2O}n (Ln = Pr for 1, Gd for 2, Ce for 3) and {[Sm(TATB)(H2O)]}n (4) (H2PBPP = 4-phenyl-2,6-bis(4′-carboxyphenyl)pyridine, H3TATB = 4,4′,4′′-s-triazine-2,4,6-tribenzoic acid). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complexes 1–3 are isomorphous and exhibit an unprecedented (4,6,6)-connected 3D architecture, which is built up from lanthanide-oxide chains. Complex 4 shows a 3D (6,6)-connected net with (44.67.84)6(48.67) topology, in which TATB3− is extremely unsymmetrical due to three metal-oxide chains in the directions of [101], [101] and [110]. Moreover, their luminescent properties have been investigated.

Water adsorption and decomposition on stoichiometrically perfect and oxygen vacancy containing ZnGa2O4 (100), (110), and (111) surfaces were investigated through periodic density functional theory (DFT) calculations. The results demonstrated that water adsorption and decomposition are surface-structure-sensitive processes. On a stoichiometrically perfect surface, the most stable molecular adsorption that could take place involved the generation of hydrogen bonds. For dissociative adsorption, the adsorption energy of the (111) surface was more than 4 times the energies of the other two surfaces, indicating it to be the best surface for water decomposition. A detailed comparison of these three surfaces showed that the primary reason for this observation was the special electronic state of the (111) surface. When water dissociated on the (111) surface, the special Ga3c-4s and 4p hybridization states at the Fermi level had an obvious downshift to the lower energies. This large energy gain greatly promoted the dissociation of water. Because the generation of O3c vacancy defects on the (100) and (110) surfaces could increase the stability of the dissociative adsorption states with few changes to the energy barrier, this type of defect would make the decomposition of water molecules more favorable. However, for the (111) surface, the generation of vacancy defects could decrease the stability of the dissociative adsorption states and significantly increase their energy barriers. Therefore, the decomposition of water molecules on the oxygen vacancy defective (111) surface would be less favorable than the perfect (111) surface. These findings on the decomposition of H2O on the ZnGa2O4 surfaces can be used toward the synthesis of water-splitting catalysts.

In general, the presence of shared edges of polyhedra for high-valence low-coordinated small cations is rarely seen except under extreme conditions such as high pressure. However, the ambient-pressure synthesis of KZnB3O6 built of edge-sharing BO4 tetrahedra is contrary to this. By investigating the molecular dynamics, lattice dynamics, and electronic properties via density functional theory, we studied the origin of the phase stability of the edge-sharing (es) and “corner-sharing (cs)” KZnB3O6. Lattice dynamics results show that there are no phonon anomalies that could lead to the instability of es-KZnB3O6, which is consistent with molecular dynamics analysis. For “cs-KZnB3O6”, a soft mode at the G point in the phonon dispersion is identified that reflects the dynamic instability with respect to small distortions. Eigenvector analysis of the soft mode of “cs-KZnB3O6” indicates that the instability comes from the linkage of ZnO5 polyhedra rather than BOx polyhedra. Electronic property calculation indicates that the edge-sharing BO4 polyhedra connected by the longest B–O σ bonds provide a solid framework for es-KZnB3O6. In the case of “cs-KZnB3O6”, the overlong Zn–O bond possesses the smallest covalent nature and the least orbital overlap among the bonds in a ZnO5 polyhedron, and these two features of the electronic structure reduce the stability of “cs-KZnB3O6” compared to es-KZnB3O6. The electronic property calculation further confirms the results obtained from lattice dynamics analysis.

An understanding of the interaction between Zn2GeO4 and the CO2 molecule is vital for developing its role in the photocatalytic reduction of CO2. In this study, we present the structure and energetics of CO2 adsorbed onto the stoichiometric perfectly and the oxygen vacancy defect of Zn2GeO4 (010) and (001) surfaces using density functional theory slab calculations. The major finding is that the surface structure of the Zn2GeO4 is important for CO2 adsorption and activation, i.e., the interaction of CO2 with Zn2GeO4 surfaces is structure-dependent. The ability of CO2 adsorption on (001) is higher than that of CO2 adsorption on (010). For the (010) surface, the active sites O2c···Ge3c and Ge3c–O3c interact with the CO2 molecule leading to a bidentate carbonate species. The presence of Ge3c–O2c···Ge3c bonds on the (001) surface strengthens the interaction of CO2 with the (001) surface, and results in a bridged carbonate-like species. Furthermore, a comparison of the calculated adsorption energies of CO2 adsorption on perfect and defective Zn2GeO4 (010) and (001) surfaces shows that CO2 has the strongest adsorption near a surface oxygen vacancy site, with an adsorption energy −1.05 to −2.17 eV, stronger than adsorption of CO2 on perfect Zn2GeO4 surfaces (Eads = −0.91 to −1.12 eV) or adsorption of CO2 on a surface oxygen defect site (Eads = −0.24 to −0.95 eV). Additionally, for the defective Zn2GeO4 surfaces, the oxygen vacancies are the active sites. CO2 that adsorbs directly at the Vo site can be dissociated into CO and O and the Vo defect can be healed by the oxygen atom released during the dissociation process. On further analysis of the dissociative adsorption mechanism of CO2 on the surface oxygen defect site, we concluded that dissociative adsorption of CO2 favors the stepwise dissociation mechanism and the dissociation process can be described as CO2 + Vo → CO2δ−/Vo → COadsorbed + Osurface. This result has an important implication for understanding the photoreduction of CO2 by using Zn2GeO4 nanoribbons.

We have employed DFT calculations to carry out an accurate analysis of the effect of N- and NH-doping on the visible photocatalytic activity in the cubic In2O3. In the substitutional N-doped In2O3, the 2p impurity states of N induce a red shift in the optical absorption, while in the interstitial N-doping the red shift is dominantly caused by the localized π antibonding states of NO. When a H atom is accompanied by a N impurity in the lattice, the H atom acts as a charge donor and compensates the hole state created by N-doping, thus the energy level of the impurity states is reduced. As a result, the mixing of impurity states and the valence band is enhanced. At the same nitrogen dopant concentration, NH-codoping yields a larger band gap narrowing, especially for the interstitial NH-codoping. The theoretical calculations presented in this work explain well the previous experimental results of the enhanced visible photocatalytic activity in NH-codoped cubic In2O3.

First-principles calculations of the electronic, optical properties and lattice dynamics of tantalum oxynitride are performed with the density functional theory plane-wave pseudopotential method. The analysis of the electronic structure shows a covalent nature in Ta−N bonds and Ta−O bonds. The hybridization of anion 2p and Ta 5d states results in enhanced dispersion of the valence band, raising the top of the valence band and leading to the visible-light response in TaON. It has a high dielectric constant, and the anisotropy is displayed obviously in the lower energy region. Our calculation indicated that TaON has excellent dielectric properties along [010] direction. Various optical properties, including the reflectivity, absorption coefficient, refractive index, and the energy-loss spectrum are derived from the complex dielectric function. We also present phonon dispersion relation, zone-center optical mode frequency, density of phonon states, and some thermodynamic properties. The experimental IR modes (Bu at 808 cm−1 and Au at 863 cm−1) are reproduced well and assigned to a combination of stretching and bending vibrations for the Ta−N bond and Ta−O bond. The thermodynamic properties of TaON, such as heat capacity and Debye temperature, which were important parameters for the measurement of crystal physical properties, were first given for reference. Our investigations provide useful information for the potential application of this material.

Two different mechanisms for improving photo-catalytic activity in different types of F-doped ZnWO4 are tentatively proposed, based on density function theory calculations. When the lattice O atom is substituted by one F atom, our calculations show that a reduced W5+ center adjacent to the doped F atom will act as a trap for the photo-induced electron, and will thus result in a reduction of electron–hole recombination and improvement of the photo-catalytic activity. For the interstitial F-doped model, partial F 2p states mixing with O 2p states localize above the top of the valence band and act as the frontier orbital level. Electronic transitions from these localized states induce a red shift of about 54 nm of the optical absorption edge. This work shows that F-doped ZnWO4 will be a promising photo-catalyst with favorable photo-catalytic activity in the UV region.Graphical AbstractDFT calculations are used to investigate the origin of the improved photo-activity of monoclinic ZnWO4 induced by the substituted and interstitial F-doping. Two possible mechanisms are tentatively put forward according to the F-doping types.

Nitrogen defects and their effect on the ferromagnetism (FM) in Cr-doped GaN have been systematically investigated by first-principles. Four considered configurations including one N vacancy (VN), single substitutional Cr, double substitutional Cr, and complex of Cr–VN are all ferromagnetic. The lowest energy arrangements for double Cr-doped (or Cr–VN) GaN occur at the nearest Cr–Cr (or Cr–VN) distance. One Cr contributes 84.3% of the total magnetic moment (2.533 μB), while one Cr–Cr pair leads to 5.998 μB moment (more than twice moment of one Cr) by the strong d–d spin coupling, which is mediated by two Cr 3d states antiferromagnetically coupling with the “commonly shared” N 2p states, and driven by a double exchange mechanism. The VN can enhance the FM by adding about 1 μB to the Cr moment but reduce the FM spin exchange interaction between the nearest Cr–Cr pairs, so experimentally, high-performance samples may be synthesized by controlling N pressure.Nitrogen defects and their effect on the ferromagnetism in Cr-doped GaN were investigated by first-principles. Given are the PDOS of Ga36N36 with one Cr–Cr pair and one complex of Cr–VN.

First-principles calculations of the electronic, optical, and lattice dynamic properties of c-BC2N, w-BC2N, cp-BC2N, z-BC2N, and t-BC2N were performed with the density functional theory (DFT) plane-wave pseudopotential method. It is found that the difference in electronic structures and optical properties is arising from the different numbers and species of chemical bonds in the five phases. The vibration analysis shows three main frequency regions arising from different relative movements among the B, C, and N atoms for the five phases. The calculation demonstrates that z-BC2N and t-BC2N have more vibration states and own much higher vibration frequencies. The experimental Raman peak, well reproduced in z-BC2N and t-BC2N, has been assigned to be the serious relative translational movements of C atoms (C1 and C3 for z-BC2N; C2 and C3 for t-BC2N) along the z direction with the other atoms moving slightly. Though the five phases may not display excellent heat capacities in room temperature (about 30 J/mol/K), the high Debye temperatures, reaching about 1700 K, may lead to some research and application interests in the thermodynamic aspect.

DFT calculations are used to investigate the origin of the experimentally observed changes in the visible photoactivity of cubic and rhombic In2O3 induced by N doping. Two possible mechanisms for the red shift in N-doped In2O3 are tentatively put forward, according to the doping types. For substitutional N-doping models, our results show that, in both polymorphs, partial N 2p states mix with O 2p states and localized lie above the top of the valence band, acting as the frontier orbital level. Electronic transitions from these localized states induce a red shift to the visible region of the optical absorption edge. For interstitial N-doping models, NO π-antibonding states localized in the gap contribute to the impurity levels. The electronic transition from these states may well explain the mechanism of the red shift in interstitial N-doped In2O3. The calculated optical properties for all N-doped In2O3 show a significant visible light absorption at about 400−600 nm, which corresponds to the experimental result. This present work shows that N-doped In2O3 will be a promising photocatalyst with favorable photocatalytic activity in the visible region.

We present a detailed investigation on the optical properties, including dielectric function, reflectivity, absorption, refractive index, and electron energy-loss spectrum, of the high-pressure phase SnO2 in the rutile, pyrite, fluorite, and cotunnite structures by using the density functional theory (DFT) plane-wave pseudopotential method. The results indicate that with the increasing of pressure the band gaps become larger, the density of states are broader, so the curves of optical properties have a little blue shift. Except that the fluorite phase has some metallic properties, the other three phases exhibit excellent dielectric behavior. Interestingly, the fluorite and cotunnite SnO2 phases always have some special characteristics, such as higher plasma frequency, which need further fundamental and application research.

A 120 ns replica-exchange molecular dynamics simulation in explicit solvent is performed to probe the conformational transitions in 5′-GGGCGCAAGCCU-3′ RNA GCAA tetraloop. The ample structural transition information of the loop is detected on the basis of extensive clustering analysis. The resultant loop structural transition map nicely agrees with the recent ultrafast fluorescence measurement, which confirms the dynamical properties of this tetraloop. Moreover, a new transition pattern that was not disclosed previously is predicted. Meanwhile, the folding free energy landscapes were characterized: the global folding dynamics is coupled mainly with the stem rather than the loop part.

We performed density functional calculations on the electronic properties of P-doped spinel silicon carbon nitride. When Si is replaced by C at the tetrahedral sites of P-doped c-Si3N4, the band gap can be adjusted, and an insulator-to-metal transition is predicted to occur at the C-to-Si ratio of 0.27. Finally, some possible examinations and potential applications for the large band-gap reduction are discussed.We performed density functional calculations to predict the insulator-to-metal transition by replacing Si by C at the tetrahedral sites of P-doped c-Si3N4.

Structural, electronic, and optical properties of various N-doped SnO2 were investigated using first-principles calculations. The calculated formation energies show that both the substitutional and the interstitial N atoms are preferentially occupied in anion sites, while the N defect formation energies in the O-rich conditions are much lower than that in the Sn-rich ones. The electronic structures demonstrate that three mechanisms are possible with regard to the red-shift of photoluminescence. The first is that the band gap width reduces because of N2p repulsing O2p states and raising up the top of valence band (EV) with N substituting for Sn; the second is that some N2p gap states are induced by N substituting for O resulting in the band gap reducing; and the third is N2p states lowering the bottom of the conduction band (EC) leading to the reduction of band gap by introducing a interstitial N. On the basis of the calculated formation energy and experimental results, the red-shift phenomenon should not be the transition from band to band but the band to gap states. The red-shift mechanism should be N2p gap states to band transition.

In order to investigate the effects of the structure of branches on the TPA properties for multi-branched molecules, the TPA cross section is calculated by using ZINDO/SOS method. The investigated molecules have different branches (chomorfores based on stilbene, dithienothiophene and flourene) with nitrogen(N) as coupling center. The results show that the cooperative enhancement in multi-branched molecules depends on the structures of the branches and the structures of branches play an important role in the enhancement of the TPA cross section. The designed molecules with stilbene and dithienothiophene as branched possess relatively larger two-photon absorption cross sections.

The zircon-type tetragonal (t-) LaVO4 nanowires were controlled synthesized by a new approach, a microemulsion-mediated hydrothermal method, in which the aqueous cores of sodium dodecyl sulfate (SDS)/cyclohexane/n-hexanol/water microemulsion were used as constrained microreactors for a controlled growth of t-LaVO4 nanocrystals under hydrothermal conditions. The microemulsion exists stably just at room temperature and not under hydrothermal conditions, in addition, the as-obtained nanowires are much larger than the microemulsion droplets, so that the microemulsion does not simply act as a template, but rather directs crystal growth into nanowires presumably by interacting with the surface of the growing crystal. A series of experimental results indicated that several experimental parameters, such as the SDS concentration, the species and content of the cosurfactant play important roles in the morphological control of the t-LaVO4 nanocrystals. Possible formation mechanism of t-LaVO4 nanowires is also discussed.The zircon-type tetragonal (t-) LaVO4 nanowires were controlled synthesized by a microemulsion-mediated hydrothermal method, in which the aqueous cores of SDS/cyclohexane/n-hexanol/water microemulsion were used as constrained microreactors for a controlled growth of t-LaVO4 nanocrystals under hydrothermal conditions.

In this paper, one- and two-photon absorption properties as well as the transition nature of a series of donor-π-acceptor-type compounds with trivalent boron as an acceptor have been theoretically studied by using INDO/SDCI method. Our calculations indicate that the four o-methyl moieties on the two mesityl groups play an important part in protecting the trivalent boron from being attacked by oxygen in the air. The trivalent boron containing group can be an all-right electron-acceptor with some bulky groups attached to it. On the basis of geometry optimization and UV–vis spectra, the positions and strengths of two-photon absorption for these molecules were reported.

The solvothermal reactions of terphenyl-2,5,2′,5′-tetracarboxylic acid (H4tptc) and transition metal cations (NiII, MnII) afford five novel coordination polymers (CPs) in the presence of four bis(imidazole) bridging ligands (1,3-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, 1,4-bmib = 1,4-bis(2-methylimidazol-1-ylmethyl)benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl, 4,4′-bimbp = 4,4′-bis(imidazol-1-ylmethyl)biphenyl), namely, [M(tptc)0.5(1,3-bimb)(H2O)]n (M = Ni for 1, Mn for 2), {[Ni(tptc)0.5(1,4-bmib)]·0.25H2O}n (3), {[Ni(tptc)0.5(4,4′-bibp)2(H2O)]·2H2O}n (4) and {[Ni(tptc)0.5(4,4′-bimbp)1.5(H2O)]·H2O}n (5). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complexes 1 and 2 are isomorphous and exhibit a 3D (3,4)-connected tfi framework with the point Schläfli symbol of (4·62)(4·66·83). Complex 3 shows an unprecedented 3D (4,4)-connected framework with the point Schläfli symbol of (4·64·82)2(42·84). Complex 4 displays a novel 2D self-catenating 5-connected network with the Schläfli symbol of (46·64) based on three interpenetrating 44-sql subnets. Complex 5 features a 2D 3-connected 63-hcb network built from interesting chains with loops. To the best of our knowledge, the 3D (4,4)-connected (4·64·82)2(42·84) host-framework of 3 and 2D self-catenating 5-connected (46·64) network of 4 have never been documented to date. Moreover, the UV-Visible absorption spectra of complexes 1–5 have been investigated.

A novel-type 3D polyoxomolybdate–organic framework, {[Cu3(H3tpb)2(tpb)(Mo4O12)]·4H2O}n (1, H3tpb = 1,3,5-tri(1H-pyrazol-3-yl)benzene), was prepared and characterized by elemental analysis, IR spectroscopy, and luminescence analysis. Single-crystal X-ray diffraction analysis reveals that novel neutral triple helix {Mo4O12}n chains are encased in bowl-like 2D [Cu3(H3tpb)2(tpb)]n intervals via bond interactions between terminal oxygen atoms and cations of Cu(I), leaving an unprecedented (3,3,5,8)-connected (3·4·68)3(36·46·86·96·104)(43)2(63) topology. Moreover, compound 1 exhibits remarkable photocatalytic activities for decomposition of methylene orange (MO), methylene red (MR), methylene blue (MB), methylene violet (MV), and rhodamine B (RhB) under UV light.

We have employed DFT calculations to carry out an accurate analysis of the effect of N- and NH-doping on the visible photocatalytic activity in the cubic In2O3. In the substitutional N-doped In2O3, the 2p impurity states of N induce a red shift in the optical absorption, while in the interstitial N-doping the red shift is dominantly caused by the localized π antibonding states of NO. When a H atom is accompanied by a N impurity in the lattice, the H atom acts as a charge donor and compensates the hole state created by N-doping, thus the energy level of the impurity states is reduced. As a result, the mixing of impurity states and the valence band is enhanced. At the same nitrogen dopant concentration, NH-codoping yields a larger band gap narrowing, especially for the interstitial NH-codoping. The theoretical calculations presented in this work explain well the previous experimental results of the enhanced visible photocatalytic activity in NH-codoped cubic In2O3.

Four new coordination polymers, namely [Co(H2O2abtc)(bibp)]n (1), {[Mn1.5(Oabtc)(H2O)2]·(H2bmib)0.5·H2O}n (2), {[Cd1.5(O2abtc)]·(H2bmib)0.5·2H2O}n (3), and {[Cd(nip)(bibp)]·0.5H2O}n (4),were constructed under solvothermal conditions in the presence of two bis(imidazole) bridging linkers (bimb = 1,4-bis(2-methylimidazol-1-ylmethyl)benzene, bibp = 4,4′-bis(imidazol-1-yl)biphenyl). The unstable azo ligand of 3,3′,5,5′-azobenzenetetracarboxylic acid (H4abtc) could be oxidized and resulted in three oxidized derivatives of H4Oabtc (one N atom was oxidized), H4O2abtc (two N atoms were oxidized), and H2nip (one H4abtc was oxidized to two 5-nitroisophthalic acids). Their structures were determined by single-crystal X-ray diffraction and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Complex 1 exhibited an interestingly 2D + 2D → 3D parallel entangled network based on 4-connected (44·62)-sql sheets. Complex 2 was found to be a {Mn3(COO)6} trinuclear SBU based 2D (3,6)-connected (43)2(46·66·83)-kgd sheet. While complex 3 displays a {Cd3(COO)8} trinuclear SBUs based 3D (4,8)-connected (46)2(412·612·84)-flu network. Complex 4 can be regard as a {Cd2(COO)2} binuclear SBUs based 6-connected (44·611)-6T8 framework. In addition, the magnetic property of complexes 1, 2 and the luminescence properties of complexes 3, 4 were investigated.

High-performance piezoelectric materials are desirable for piezoelectric sensing applications. In this paper, piezoelectric α-BiB3O6 (BIBO) crystals were explored for high temperature sensing. Dielectric, piezoelectric and electromechanical properties were evaluated by using the impedance method, from which the piezoelectric charge coefficients were determined to be d14 = 10.9, d16 = 13.9, d21 = 16.7, d22 = 40.0, d23 = 2.5, d25 = 4.3, d34 = 18.7 and d36 = 13.0 pC/N, with corresponding piezoelectric voltage coefficients g14 = 122, g16 = 144, g21 = 225, g22 = 538, g23 = 34, g25 = 58, g34 = 165 and g36 = 121 × 10−3 V m N−1 at room temperature (RT). Of particular significance is that the receiving sensitivity of BIBO crystals was found to be 47.2 pm2 N−1, nearly one order of magnitude higher than that of LiNbO3 crystals. Moreover, the BIBO crystals were found to possess a high mechanical quality factor Qm (13000 at RT and >1000 at 600 °C), low dielectric loss (<0.1% at RT and 15% at 600 °C and 1 kHz), high electrical resistivity (∼2.5 × 108 Ω cm at 600 °C) and high temperature stability of piezoelectric coefficients (variations <±10%). All these properties demonstrate that BIBO crystals are promising for piezoelectric sensing over a broad temperature range.

Solvothermal reactions of the semirigid 3,5-bi(4-carboxyphenoxy)benzoic acid (H3BCP) and transitional metal cations with the help of three ancillary bridging imidazole linkers afforded six coordination polymers, namely, [Co(HBCP)(1,4-bib)0.5]n (1), {[Mn1.5(BCP)(1,4-bib)0.5(μ2-H2O)(H2O)2]·(1,4-bib)0.5}n (2), {[Mn0.5(1,4-bib)(H2O)]·(H2BCP)}n (3), {[Fe(BCP)0.5(HCOO)0.5(4,4′-bibp)0.5]·2H2O}n (4), [Ni2.5(HBCP)(BCP)(4,4′-bibp)2(μ2-H2O)(H2O)2]n (5), and [Ni(HBCP)(1,4-bidb)1.5(H2O)2]n (6), (1,4-bib = 1,4-bis(1H-imidazol-4-yl)benzene, 1,4-bidb = 1,4-bis(1-imidazol-yl)-2,5-dimethyl benzene, 4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl). Their structures and properties were determined by single-crystal and powder X-ray diffraction analyses, IR spectra, elemental analyses, thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS). Complex 1 displays unusual 2D + 2D→2D parallel entangled networks consisting of (3,4)-connected 3,4L83 sheets. Complex 2 exhibits an interesting 2-fold interpenetrated framework with a trinodal (4,4,6)-connected (3·4·5·62·7)2(3·6·74)2(32·42·52·62·76·9) topology. The host network of complex 3 is a 2D 4-connected (44·62)-sql sheet. Complex 4 affords unprecedented 3D (4,6,6)-coordinated framework with point symbol of (45·6)(48·67)(49·63·83)2, in which the 1D helix water chains occupy the void channels. Complex 5 can be regarded as a novel self-penetrating (4,4,4,5)-coordinated framework with point symbol of (4·54·6)2(4·65·7·83)2(5·6·7·83)2(52·83·92), which contains two interpenetrated (3,4,4,5)-coordinated (4·54·6)2(4·65·7·83)2(5·6·7)2(52·83·92) subnets linked by μ2-H2O. Complex 6 shows a 1D ladder chain, which are further assembled into a 3D supramolecular structure via O–H⋯O and π⋯π interactions. Moreover, magnetic studies indicate that both complex 2 and 4 show antiferromagnetic properties.