Nanocage-Based Tb³⁺-Organic Framework for Efficiently Catalyzing the Cycloaddition Reaction of CO₂ with Epoxides and Knoevenagel Condensation

The catalytic performance of metal–organic framework (MOF)-based catalysts can be enhanced by increasing their catalytic sites, which prompts us to explore the multicore cluster-based skeletons by using designed functional ligands. Herein, the exquisite combination of [Tb4(μ2–OH)2(CO2)8] cluster and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H5BDCP) ligand generated a highly robust nanoporous framework of {[Tb4(BDCP)2(μ2–OH)2]·3DMF·5H2O}n (NUC-58), in which each four {Tb4} clusters are woven together to generate an elliptical nanocage (aperature ca. 12.4 Å). As far as we know, NUC-58 is an excellent nanocage-cluster-based {Tb4}-organic framework with the outstanding confined pore environments of a large specific surface area, high porosity, and plentiful coexisting Lewis acid–base sites of Tb3+, μ2–OH and Npyridine atoms. Performed experiments exhibited that NUC-58 owns a better catalytic performance for the cycloaddition reactions under mild conditions with a high turnover number and turnover frequency. Furthermore, NUC-58, as an eminent heterogeneous catalyst, can enormously boost the Knoevenagel condensation reactions. Thus, this work opens a path for the precise design of polynuclear metal cluster-based MOFs with excellent catalysis, stability, and regenerative behavior

Robust Heterometallic Tb^III/Mn^II–Organic Framework for CO₂/CH₄ Separation and I₂ Adsorption

The exquisite combination of heterometallic [TbIIIMnII(CO2)3(H2O)2] clusters with the hexacarboxylate ligand of H6TDP generates one water-stable 3D heterometallic TbIII/MnII-organic framework material {TbMn­(HTDP)­(H2O)2]·5DMF·4H2O}n (NUC-3; H6TDP = 2,4,6-tri­(2′,4′-dicarboxyphenyl)­pyridine), which consists of functionalized noninterspersed opening nanochannels shaped by six rows of [TbIIIMnII(CO2)3(H2O)2] clusters. Based on the single-component sorption measurements, activated NUC-3 framework exhibits effective CO2/CH4 separation associated with high uptake and moderate adsorption enthalpy of CO2. Dynamic breakthrough experiments reveal that NUC-3 could be competent for the separation of CO2/CH4 (50:50, v:v) mixture. Moreover, the kinetic and equilibrium experiments of iodine adsorption indicate that NUC-3 possess excellent adsorption capacity for iodine molecules in cyclohexane solution. The excellent structural stability and functional internal surface makes NUC-3 a prospective adsorbent for practical CO2/CH4 separation and adsorption elimination of iodine molecules, opening up the insight of heterometallic MOFs for pratical application

Highly Robust {In₂}–Organic Framework for Efficiently Catalyzing CO₂ Cycloaddition and Knoevenagel Condensation

To improve the catalytic performance of metal–organic frameworks (MOFs), creating higher defects is now considered as the most effective strategy, which can not only optimize the Lewis acidity of metal ions but also create more pore space to enhance diffusion and mass transfer in the channels. Herein, the exquisite combination of scarcely reported [In2(CO2)5(H2O)2(DMF)2] clusters and 2,6-bis­(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)­pyridine (H5BDCP) under solvothermal conditions generated a highly robust nanoporous framework of {[In2(BDCP)­(DMF)2(H2O)2]­(NO3)}n (NUC-65) with nanocaged voids (14.1 Å) and rectangular nanochannels (15.94 Å × 11.77 Å) along the a axis. It is worth mentioning that an In(1) ion displays extremely low tetra-coordination modes after the thermal removal of its associated four solvent molecules of H2O and DMF. Activated {[In2(BDCP)]­(Br)}n (NUC-65Br), as a defective material because of its extremely unsaturated metal centers, could be generated by bromine ion exchange, solvent exchange, and vacuum drying. Catalytic experiments proved that the conversion of epichlorohydrin with 1 atm CO2 into 4-(chloromethyl)-1,3-dioxolan-2-one catalyzed by 0.11 mol % NUC-65Br could reach 99% at 65 °C within 24 h. Moreover, with the aid of 5 mol % cocatalyst n-Bu4NBr, heterogeneous NUC-65Br owns excellent universal catalytic performance in most epoxides under mild conditions. In addition, NUC-65Br, as a heterogeneous catalyst, exhibits higher activity and better selectivity for Knoevenagel condensation of aldehydes and malononitrile. Hence, this work offers a fresh insight into the design of structure defect cationic metal–organic frameworks, which can be better applied to various fields because of their promoted performance

Robust Heterometallic Tb^III/Mn^II–Organic Framework for CO₂/CH₄ Separation and I₂ Adsorption

The exquisite combination of heterometallic [TbIIIMnII(CO2)3(H2O)2] clusters with the hexacarboxylate ligand of H6TDP generates one water-stable 3D heterometallic TbIII/MnII-organic framework material {TbMn­(HTDP)­(H2O)2]·5DMF·4H2O}n (NUC-3; H6TDP = 2,4,6-tri­(2′,4′-dicarboxyphenyl)­pyridine), which consists of functionalized noninterspersed opening nanochannels shaped by six rows of [TbIIIMnII(CO2)3(H2O)2] clusters. Based on the single-component sorption measurements, activated NUC-3 framework exhibits effective CO2/CH4 separation associated with high uptake and moderate adsorption enthalpy of CO2. Dynamic breakthrough experiments reveal that NUC-3 could be competent for the separation of CO2/CH4 (50:50, v:v) mixture. Moreover, the kinetic and equilibrium experiments of iodine adsorption indicate that NUC-3 possess excellent adsorption capacity for iodine molecules in cyclohexane solution. The excellent structural stability and functional internal surface makes NUC-3 a prospective adsorbent for practical CO2/CH4 separation and adsorption elimination of iodine molecules, opening up the insight of heterometallic MOFs for pratical application

Heterometallic YbCo–Organic Framework for Efficiently Catalyzing Cycloaddition of CO₂ with Epoxides and Knoevenagel Condensation

Due to the excellent catalytic performance of Co-MOFs and Ln-MOFs on the chemical fixation of CO2, the self-assembly of microporous heterometallic compounds with the aid of designed functional ligands is carried out in our group. Herein, the solvothermal self-assembly of Co2+, Yb3+, and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H5BDCP) generated a rarely reported {CoYb}n-chain-based framework of {[CoYb(BDCP)(H2O)]·3DMF·3H2O}n (NUC-70) with quasi-nanoporous channels (aperture ca. 11.4 Å) shaped by six rows of {CoYb(CO2)5(H2O)}n nodes. To the best of our knowledge, this is a rare 3d-4f heterometallic chain of {CoYb(CO2)5(H2O)}n with a staggered arrangement of Co2+ and Yb3+. After removing the associated water molecules, NUC-70a possesses the excellent characteristics of a large specific surface area, unsaturated open metal sites of Co2+ and Yb3+ as Lewis acid sites, and high heat/water-resistant physicochemical properties. Catalytic experiments showed that NUC-70a possessed a high catalytic activity on the cycloaddition reactions of epoxides with CO2 under mild conditions. Furthermore, the experiments performed confirmed that the Knoevenagel condensation reactions of aldehydes and malononitrile could be efficiently catalyzed by NUC-70a. This work illustrates that characteristic ligand design plays a key role in the self-assembly of MOFs with specific functions

Robust Nitro-Functionalized {Zn₃}‑Organic Framework for Excellent Catalytic Performance on Cycloaddition Reaction of CO₂ with Epoxides and Knoevenagel Condensation

Adjusting the Lewis acid–base sites in MOF-based catalysts to meet the demand for catalytic CO2 chemical fixation is a huge challenge. Herein, a highly robust rectilinear {Zn3}-based metal–organic framework of {[Zn3(TNTNB)2(4,4′-bip)(H2O)2]·5DMF·9H2O}n (NUC-80) was generalized from the solvothermal condition (H3TNTNB = 1,3,5-tri(3-nitro-4-carboxyphenyl)-2,4,6-trinitrobenzene, 4,4′-bip = 4,4′-bipyridine). Activated NUC-80a not only owns the large void volume (58%) and two kinds of solvent-accessible channels: rhombic-like (ca. 14.24 × 14.57 Å) along a axis and rectangular-like (ca. 11.72 × 14.48 Å) along b axis, but also is functionalized by rich metal sites and plentiful nitro groups on its inner surface. Performed catalytic experiments confirmed that NUC-80a could efficiently catalyze the cycloaddition reaction of CO2 with epoxides and Knoevenagel condensations of aldehydes and malononitrile under mild conditions with a high turnover frequency (TOF). Hence, this work provides a nitro-functionalized metal cluster-based nanoporous metal–organic framework with a wide range of potential applications such as catalysis, gas adsorption, and separation

Brain regions that showed significant alterations in fALFF before and after HD-tDCS.

(P pre-HD-tDCS in the fALFF values and the blue color denotes post-HD-tDCS < pre-HD-tDCS. The T-value bars are shown at the bottom. The brain regions with significant increases in fALFF include Temporal Inf R, Fusiform L, Occipital Sup L, Calcarine R, Angular R. However, Insula R, Precuneus R, Thalamus L, and Parietal Sup R decreased significantly. fALFF, fractional amplitude of low-frequency fluctuation; HD-tDCS, high-definition transcranial direct current stimulation.</p

The results of the neuropsychological assessment pre-post intervention in both MCI groups.

The results of the neuropsychological assessment pre-post intervention in both MCI groups.</p

Ancillary Ligands Dependent Structural Diversity of A Series of Metal–Organic Frameworks Based on 3,5-Bis(3-carboxyphenyl)pyridine

A series of novel multidimensional transition metal–organic frameworks (MOFs), [Cu­(Hbcpb)₂]_<i>n</i> (<b>1</b>), [Co­(bcpb)]_<i>n</i> (<b>2</b>), [Co­(Hbcpb)₂(1,4-bib)]<i>n</i> (<b>3</b>), {[M­(bcpb)­(1,4-bimb)]·xH₂O}<i>n</i> (<i>M</i> = Co (<b>4</b>), Cu (<b>5</b>), Ni (<b>6</b>), <i>x</i> = 1 for <b>5</b>, 2 for <b>4</b> and <b>6</b>), [Co­(bcpb)­(4,4′-bibp)]_<i>n</i> (7), {[Co­(bcpb)­(4,4′-bibp)]·2H₂O}_<i>n</i> (<b>8</b>), and [Ni₂(bcpb)₂(4,4′-bimbp)₂]_<i>n</i> (<b>9</b>), 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 <b>1</b> and <b>3</b>, and completely deprotonated to afford the bcpb^2– form in <b>2</b> and <b>4</b>–<b>9</b>. Complex <b>1</b> 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 <b>2</b> is defined as a (4,4)-connected pts topology with the Schläfli symbol of (4²·8⁴). Complex <b>3</b> 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 <b>4</b>–<b>6</b> 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 <b>7</b> and <b>8</b>, 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 <b>9</b> 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

Ancillary Ligands Dependent Structural Diversity of A Series of Metal–Organic Frameworks Based on 3,5-Bis(3-carboxyphenyl)pyridine

A series of novel multidimensional transition metal–organic frameworks (MOFs), [Cu­(Hbcpb)₂]_<i>n</i> (<b>1</b>), [Co­(bcpb)]_<i>n</i> (<b>2</b>), [Co­(Hbcpb)₂(1,4-bib)]<i>n</i> (<b>3</b>), {[M­(bcpb)­(1,4-bimb)]·xH₂O}<i>n</i> (<i>M</i> = Co (<b>4</b>), Cu (<b>5</b>), Ni (<b>6</b>), <i>x</i> = 1 for <b>5</b>, 2 for <b>4</b> and <b>6</b>), [Co­(bcpb)­(4,4′-bibp)]_<i>n</i> (7), {[Co­(bcpb)­(4,4′-bibp)]·2H₂O}_<i>n</i> (<b>8</b>), and [Ni₂(bcpb)₂(4,4′-bimbp)₂]_<i>n</i> (<b>9</b>), 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 <b>1</b> and <b>3</b>, and completely deprotonated to afford the bcpb^2– form in <b>2</b> and <b>4</b>–<b>9</b>. Complex <b>1</b> 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 <b>2</b> is defined as a (4,4)-connected pts topology with the Schläfli symbol of (4²·8⁴). Complex <b>3</b> 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 <b>4</b>–<b>6</b> 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 <b>7</b> and <b>8</b>, 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 <b>9</b> 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