Eu(III) functionalized ZnMOF based efficient dual-emission sensor integrated with self-calibrating logic gate for intelligent detection of epinephrine.

The rapid detection of epinephrine (EPI) in serum holds immense importance in the early disease diagnosis and regular monitoring. On the basis of the coordination post-synthetic modification (PSM) strategy, a Eu3+ functionalized ZnMOF (Eu3+@ZnMOF) was fabricated by anchoring the Eu3+ ions within the microchannels of ZnMOF as secondary luminescent centers. Benefiting from two independent luminescent centers, the prepared Eu3+@ZnMOF shows great potential as a multi-signal self-calibrating luminescent sensor in visually and efficiently detecting serum EPI levels, with high reliability, fast response time, excellentrecycleability, and low detection limits of 17.8 ng/mL. Additionally, an intelligent sensing system was designed in accurately and reliably detecting serum EPI levels, based on the designed self-calibrating logic gates. Furthermore, the possible sensing mechanisms were elucidated through theoretical calculations as well as spectral overlaps. This work provides an effective and promising strategy for developing MOFs-based self-calibrating intelligent sensing platforms to detect bioactive molecules in bodily fluids.

Nanoporous {Co3}-Organic framework for efficiently seperating gases and catalyzing cycloaddition of epoxides with CO2 and Knoevenagel condensation.

Enhancing the catalysis of metal-organic frameworks (MOFs) by regulating inherent Lewis acid-base sites to realize the efficient seperation and chemical fixation of inert carbon dioxide (CO2) is crucial but challenging. Herein, the solvothermal self-assembly of Co2+, 5'-(4-carboxy-2-nitrophenyl)-2,2',2'',4',6'-pentanitro-[1,1':3',1''-terphenyl]-4,4''-dicarboxylic acid (H3TNBTB) and 4'-phenyl-4,2':6',4''-terpyridine (PTP) generated a highly robust cobalt-organic framework of {[Co3(TNBTB)2(PTP)]·7DMF·6H2O}n (NUC-82). In NUC-82, the tri-core clusters of {Co3} with linear shape are bridged by TNBTB3- to form two-dimensional structure in ac plane, which is further linked by PTP to generate a three-dimensional framework with two kinds of solvent-accessible channels: rhombic-like (ca. 11.57 × 10.76 Å) along a axis and rectangular-like (ca. 7.32 × 11.56 Å) along b axis. Furthermore, it is worth emphasizing that the confined pore environments are characterized by plentiful Lewis acid-base sites of tricobalt clusters, grafted nitro groups and free pyridinyl, high specific surface area and solvent-free nano-caged windows. Activated NUC-82a owns the ultra-high ethylene (C2H2) separation performance over the mixture of C2H2/CH4 and CO2/CH4 with the selectivity of 223.1 and 44.7. Thanks to the great Lewis-acid sites as well as the large pore volume, activated NUC-82a displays the high catalytic performace on the cycloaddition of CO2 with epoxides under wield condtions such as amibient pressure. Furthermore, because of the rich Lewis base sites, NUC-82a can efficiently catalyze Knoevenagel condensation of aldehydes and malononitrile. In the above organic reactions, NUC-82a not only shows the high catalytic activity, but also exhibits the high selectivity, satifactory recyclability and easy-to-separate heterogeneity, confirming that NUC-82a is a promising catalyst. Hence, this work provides in-depth insight into the construction of multifunctional MOFs by modifying the traditional ligands with as many Lewis acid-base active sites as possible.

Robust Fluorine-Functionalized {Ln5}-Organic Frameworks for Excellent Catalytic Performance on Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation.

Lanthanide-organic frameworks (LnOFs) are a class of promising catalysts on a large number of organic reactions because of the higher coordination number of Ln3+ ions, inspired by which exploratory preparation of cluster-based LnOFs was carried out by us. Herein, the exquisite combination of spindly [Ln5(µ3-OH)6(CO2)6(H2O)6] clusters (abbreviated as {Ln5}) and fluorine-functionalized tetratopic ligand of 2',3'-difluoro-[p-terphenyl]-3,3″,5,5″-tetracarboxylic acid (F-H4PTTA) engendered two highly robust isomorphic nanoporous frameworks of {[Ln5(FPTTA)2(µ3-OH)6(H2O)6](NO3)}n (NUC-61, Ln = Ho and Dy). NUC-61 compounds are rarely reported {Ln5}-based 3D frameworks with nano-caged voids (19 Å × 17 Å), which are shaped by twelve [Ln5(µ3-OH)6(COO)8] clusters and eight completely deprotonated F-PTTA4- ligands. Activated NUC-61a compounds are characterized by plentiful coexisted Lewis acid-base sites of open LnIII sites, capped µ3-OH, and -F. Judged by the ideal adsorbed solution theory (IAST), activated NUC-61Ho-a had a high CO2/CH4 adsorptive selectivity with the value of 12.7 (CO2/CH4 = 50/50) and 9.1 (CO2/CH4 = 5/95) at 298 K, which could lead to high-purity CH4 (≥99.9996%). Furthermore, catalytic experiments exhibited that NUC-61Ho-a, as a representative, could efficiently catalyze the cycloaddition reactions of CO2 with epoxides as well as the Knoevenagel condensation reactions of aldehydes and malononitrile. This work proves that the {Ln5}-based skeletons of NUC-61 with chemical stability, heterogeneity, and recyclability are an excellent acid-base bifunctional catalyst for some organic reactions.

θ-[Mo8O26]4--based multifunctional hybrid material for high catalytic performance on the cycloaddition of CO2, esterification and knoevenagel condensation.

Developing materials with excellent properties has become the norm in the field of basic research, prompting us to explore highly robust hybrid materials based on electron-rich POMs and electron-deficient MOFs. Herein, a θ-[Mo8O26]4--based hybrid material of [Cu2(BPPP)2]{θ-[Mo8O26]} (NUC-62) with excellent physicochemical stability was self-assembled under acidic solvothermal conditions from Na2MoO4 and CuCl2 in the presence of a designed chelated ligand of 1,3-bis(3-(2-pyridyl)pyrazol-1-yl)propane (BPPP), which has sufficient coordination sites, spatial self-regulation and great deformation ability. In NUC-62, each of two tetra-coordinated CuII ions and two BPPP are unified into one dinuclear unit serving as the cation, which is interactively linked to θ-[Mo8O26]4- anions via rich hydrogen bonds of C-H⋯O. Because of the unsaturated Lewis acidic CuII sites, NUC-62 exhibits high catalytic performance on the cycloaddition reactions of CO2 with epoxides under mild conditions with a high turnover number and turnover frequency. Furthermore, NUC-62, as a recyclable heterogeneous catalyst, shows high catalytic activity for the esterification of aromatic acid under refluxing, which is much better than the inorganic acid catalyst of H2SO4 in terms of turnover number and turnover frequency. Moreover, because of open metal sites and rich terminal oxygen atoms, NUC-62 shows high catalytic activity for Knoevenagel condensation reactions of aldehydes and malononitrile. Hence, this study lays the groundwork for constructing heterometallic cluster-based microporous MOFs with excellent Lewis acidic catalysis and chemical stability. Therefore, this study lays a foundation for the construction of functional polyoxometalate complexes.

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.

A highly robust cluster-based indium(III)-organic framework with efficient catalytic activity in cycloaddition of CO2 and Knoevenagel condensation.

The efficient catalytic performance displayed by MOFs is decided by an appropriate charge/radius ratio of defect metal sites, large enough solvent-accessible channels and Lewis base sites capable of polarizing substrate molecules. Herein, the solvothermal self-assembly led to a highly robust nanochannel-based framework of {[In4(CPDD)2(µ3-OH)2(DMF)(H2O)2]·2DMF·5H2O}n (NUC-66) with a 56.8% void volume, which is a combination of a tetranuclear cluster [In4(µ3-OH)2(COO)10(DMF)(H2O)2] (abbreviated as {In4}) and a conjugated tetracyclic pentacarboxylic acid ligand of 4,4'-(4-(4-carboxyphenyl)pyridine-2,6-diyl)diisophthalic acid (H5CPDD). To the best of our knowledge, NUC-66 is a rarely reported {In4}-based 3D framework with embedded hierarchical triangular-microporous (2.9 Å) and hexagonal-nanoporous (12.0 Å) channels, which are shaped by six rows of {In4} clusters. After solvent exchange and vacuum drying, the surface of nanochannels in desolvated NUC-66a is modified by unsaturated In3+ ions, Npyridine atoms and µ3-OH groups, all of which display polarization ability towards polar molecules due to their Lewis acidity or basicity. The catalytic experiments performed showed that NUC-66a had high catalytic activity in the cycloaddition reactions of epoxides with CO2 under mild conditions, which should be ascribed to its structural advantages including nanoscale channels, rich bifunctional active sites, large surface areas and chemical stability. Moreover, NUC-66a, as a heterogeneous catalyst, could greatly accelerate the Knoevenagel condensation reactions of aldehydes and malononitrile. Hence, this work confirms that the development of rigid nanoporous cluster-based MOFs built on metal ions with a high charge and large radius ratio will be more likely to realize practical applications, such as catalysis, adsorption and separation of gas, etc.

Eu(III)-Functionalized MOF-Based Dual-Emission Ratiometric Sensor Integrated with Logic Gate Operation for Efficient Detection of Hippuric Acid in Urine and Serum.

With the introduction of Eu3+ ions as the secondary fluorescent signal reporter and sensing active sites, a dual-emission ratiometric sensor of Eu3+@NiMOF (Eu3+ functional NiMOF) for hippuric acid (HA) detection in urine and serum was fabricated via the postsynthetic encapsulating strategy. Based on the two emission signals at 441 nm (turn-on) and 628 nm (turn-off), the produced Eu3+@NiMOF ratiometric sensor provided enhanced sensitivity, higher selectivity, and 9.7 times lower limits of detection (LOD) for the detection of HA (2.38 µM, 0.42 µg·mL-1) than that of the pristine NiMOF. Considering the high sensitivity and visualization results, further exploration of intelligent applications in the HA sensing process was carried out by constructing a tandem combinational logic gate to improve the practicability and convenience with the help of a smartphone. This work provides a promising approach for developing MOF-based ratiometric sensors to detect biomarkers.

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.

Fluorine-Functionalized NbO-Type {Cu2}-Organic Framework: Enhanced Catalytic Performance on the Cycloaddition Reaction of CO2 with Epoxides and Deacetalization-Knoevenagel Condensation.

The high catalytic activity of metal-organic frameworks (MOFs) can be realized by increasing their effective active sites, which prompts us to perform the functionalization on selected linkers by introducing a strong Lewis basic group of fluorine. Herein, the exquisite combination of paddle-wheel [Cu2(CO2)4(H2O)] clusters and meticulously designed fluorine-funtionalized tetratopic 2',3'-difluoro-[p-terphenyl]-3,3″,5,5″-tetracarboxylic acid (F-H4ptta) engenders one peculiar nanocaged {Cu2}-organic framework of {[Cu2(F-ptta)(H2O)2]·5DMF·2H2O}n (NUC-54), which features two types of nanocaged voids (9.8 Å × 17.2 Å and 10.1 Å × 12.4 Å) shaped by 12 paddle-wheel [Cu2(COO)4H2O)2] secondary building units, leaving a calculated solvent-accessible void volume of 60.6%. Because of the introduction of plentifully Lewis base sites of fluorine groups, activated NUC-54a exhibits excellent catalytic performance on the cycloaddition reaction of CO2 with various epoxides under mild conditions. Moreover, to expand the catalytic scope, the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile were performed using the heterogenous catalyst of NUC-54a. Also, NUC-54a features high recyclability and catalytic stability with excellent catalytic performance in subsequent catalytic tests. Therefore, this work not only puts forward a new solution for developing high-efficiency heterogeneous catalysts, but also enriches the functionalization strategies for nanoporous MOFs.

Nanoporous {Y2}-Organic Frameworks for Excellent Catalytic Performance on the Cycloaddition Reaction of Epoxides with CO2 and Deacetalization-Knoevenagel Condensation.

Stable metal-organic frameworks containing periodically arranged nanosized pores and active Lewis acid-base active sites are considered as ideal candidates for efficient heterogeneous catalysis. Herein, the exquisite combination of [Y2(CO2)7(H2O)2] cluster (abbreviated as {Y2}) and multifunctional linker of 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (H6TDP) led to a nanoporous framework of {[Y2(TDP)(H2O)2]·5H2O·4DMF}n (NUC-53, NUC = North University of China), which is a rarely reported binuclear three-dimensional (3D) framework with hierarchical tetragonal-microporous (0.78 nm) and octagonal-nanoporous (1.75 nm) channels. The inner walls of these channels are aligned by {Y2} clusters and plentifully coexisted Lewis acid-base sites of YIII ions and Npyridine atoms. Furthermore, NUC-53 has a quite large void volume of ∼65.2%, which is significantly higher than most documented 3D rare-earth-based MOFs. The performed catalytic experiments exhibited that activated NUC-53 showed a high catalytic activity on the cycloaddition reactions of CO2 with styrene oxide under mild conditions with excellent turnover number (TON: 1980) and turnover frequency (TOF: 495 h-1). Moreover, the deacetalization-Knoevenagel condensation reactions of benzaldehyde dimethyl acetal and malononitrile could be efficiently prompted by the heterogeneous catalyst of NUC-53. These findings not only pave the way for the construction of nanoporous MOF based on rare-earth clusters with a variety of catalytic activities but also provide some new insights into the catalytic mechanism.

Nanochannel-based {BaZn}-organic framework for catalytic activity on the cycloaddition reaction of epoxides with CO2 and deacetalization-Knoevenagel condensation.

Herein, the rare combination of BaII (5s) and ZnII (3d) in the presence of the structure-oriented TDP6- ligand generated the nanochannel-based hybrid material {[(CH3)2NH2]2[BaZn(TDP)(H2O)]·DMF·5H2O}n (NUC-51, H6TDP = 2,4,6-tri(2,4-dicarboxyphenyl)pyridine), which possesses excellent physicochemical characteristics such as nanoscopic channels, high porosity, large specific surface area, and high heat/water-resistance. To the best of our knowledge, this is the first 3D [BaIIZnII(CO2)6(H2O)]-based nano-porous host framework, whose activated state possesses the coexistence of Lewis acid-base sites including 4-coordinated Zn2+ ions, 7-coordinated Ba2+ ions, uncoordinated carboxyl oxygen atoms, and Npyridine atoms. Catalytic experiments exhibited that activated NUC-51a possesses a high catalytic activity on the cycloaddition reactions of epoxides with CO2 at 55 °C, which can be ascribed to its structural advantages of nanoscale channels and rich bifunctional active sites. Moreover, NUC-51a could significantly accelerate the deacetalization-Knoevenagel condensation reaction in DMSO solvent at 70 °C.

Luminescent binuclear Zinc(II) organic framework as bifunctional water-stable chemosensor for efficient detection of antibiotics and Cr(VI) anions in water.

To achieve the ultrastable LMOFs with predominant luminescent sensing performances, the aromatic π-electron mixed ligands strategy was introduced, and the ternary LMOF of {[Zn2(HDDB)(bib)1.5]·3H2O}n (1), was fabricated based on 3,5-di(2',4'-dicarboxylphenyl)benozoic acid (H5DDB) and the N-donor of meta-bis(imidazol-1-yl)benzene (bib) under mixed solvothermal condition. LMOF 1 features the first reported 3D 3,4,4-c {62.83.10}{62.8}2{63.82.10}2 framework with 21.2 % porosity as well as high thermal and chemical stability. Further luminescent sensing showed that LMOF 1 as a bifunctional chemosensor possessing predominant detectability for sensitive detect the hexavalent chromates and nitroimidazoles/nitrofurans antibiotics in water through strong luminescent quenching effects, with excellent reusability as well as trace detection limits. Moreover, luminescent quenching mechanisms were further investigated from electron transfer and energy transfer viewpoints.

Investigation on the catalytic behavior of a novel thulium-organic framework with a planar tetranuclear {Tm4} cluster as the active center for chemical CO2 fixation.

Herein, the exquisite combination of coplanar [Tm4(CO2)10(µ3-OH)2(µ2-HCO2)(OH2)2] clusters ({Tm4}) and structure-oriented functional BDCP5- leads to the highly robust nanoporous {Tm4}-organic framework {(Me2NH2)[Tm4(BDCP)2(µ3-OH)2(µ2-HCO2)(H2O)2]·7DMF·5H2O}n (NUC-37, H5BDCP = 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine). To the best of our knowledge, NUC-37 is the first anionic {Ln4}-based three-dimensional framework with embedded hierarchical microporous and nanoporous channels, among which each larger one is shaped by six rows of coplanar {Tm4} clusters and characterized by plentiful coexisting Lewis acid-base sites on the inner wall including open TmIII sites, Npyridine atoms, µ3-OH and µ2-HCO2. Catalytic experimental studies exhibit that NUC-37 possesses highly selective catalytic activity on the cycloaddition of epoxides with CO2 as well as high recyclability under gentle conditions, which should be ascribed to its nanoscale channels, rich bifunctional active sites, and stable physicochemical properties. This work offers an effective means for synthesizing productive cluster-based Ln-MOF catalysts by employing structure-oriented ligands and controlling the solvothermal reaction conditions.

Nanochannel {InZn}-Organic Framework with a High Catalytic Performance on CO2 Chemical Fixation and Deacetalization-Knoevenagel Condensation.

The rare combination of InIII 5p and ZnII 3d in the presence of a structure-oriented TDP6- ligand led to a robust hybrid material of {(Me2NH2)[InZn(TDP)(OH2)]·4DMF·4H2O}n (NUC-42) with the interlaced hierarchical nanochannels (hexagonal and cylindrical) shaped by six rows of undocumented [InZn(CO2)6(OH2)] clusters, which represented the first 5p-3d nanochannel-based heterometallic metal-organic framework. With respect to the multifarious symbiotic Lewis acid-base and Brønsted acid sites in the high porous framework, the catalytic performance of activated NUC-42a upon CO2 cycloaddition with styrene oxide was evaluated under solvent-free conditions with 1 atm of CO2 pressure, which exhibited that the reaction could be well completed at ambient temperature within 48 h or at 60 °C within 4 h with high yield and selectivity. Moreover, because of the acidic function of metal sites and a central free pyridine in the TDP6- ligand, deacetalization-Knoevenagel condensation of acetals and malononitrile could be efficiently facilitated by an activated sample of NUC-42a under lukewarm conditions.

Template-Induced {Mn2}-Organic Framework with Lewis Acid-Base Canals as a Highly Efficient Heterogeneous Catalyst for Chemical Fixation of CO2 and Knoevenagel Condensation.

The target for the self-assembly of functional microporous metal-organic frameworks (MOFs) could be realized by employing ligand-directed and/or template-induced strategies, which prompted us to explore the synthetic technique of d10 secondary-building-unit-based nanoporous frameworks. Here, the exquisite combination of a paddle-wheel [Mn2(CO2)6(OH2)2] cluster and a TDP6- ligand contributes one robust honeycomb framework of {(Me2NH2)2[Mn2(TDP)(H2O)2]·3H2O·3DMF}n (NUC-31; DMF = N,N-dimethylformamide), whose activated state with the removal of associated aqueous molecules characterizes the outstanding physicochemical properties of nanochannels, penta- and tetracoordinated Mn2+ serving as highly open metal sites, rich Lewis base sites (rows of C═O groups and Npyridine atoms), and excellent thermal stability. Moreover, it is worth mentioning that Lewis acid-base sites on the inner surface of the channels in activated NUC-31 successfully form one unprecedented canal-shaped acid-base confined space with evenly distributed open metal sites of Mn2+ and Npyridine atoms as the canal bottom as well as two rows of C═O groups serving as dyke dams. Catalytic experiments displayed that activated NUC-31 could serve as an efficient heterogeneous catalyst for the chemical fixation of CO2 with epoxides into cyclic carbonates under mild conditions. Furthermore, NUC-31 could effectively catalyze the reaction Knoevenagel condensation, which should be ascribed to the synergistic polarization effect aroused from its plentiful Lewis base sites in the confined channel space. Hence, these results demonstrate that the employment of ligand-directed and template-dependent strategies could overcome the self-assembled barriers of functional microporous MOFs and achieve unexpected frameworks.

V═O Functionalized {Tm2}-Organic Framework Designed by Postsynthesis Modification for Catalytic Chemical Fixation of CO2 and Oxidation of Mustard Gas.

In terms of recently documented references, the introduction of V═O units into porous MOF/COF frameworks can greatly improve their original performance and expand their application prospects due to a change in their electronegativity. In this work, by a cation-exchange strategy, a consummate combination of separate 4f [Tm2(CO2)8] SBUs and 3d [VIVO(H2O)2] units generated the functionalized porous metal-organic framework {(Me2NH2)2[VO(H2O)][Tm2(BDCP)2]·3DMF·3H2O}n (NUC-11), in which [Tm2(CO2)8] SBUs constitute the fundamental 3D host framework of {[Tm2](BDCP)2}n along with [VIVO(H2O)2] units being further docked on the inner wall of channels by covalent bonds. Significantly, NUC-11 represents the first example of V═O modified porous MOFs, in which uncoordinated carboxylic groups (-CO2H) further grasp the functional [VIVO(H2O)2] units on the initial basic skeleton along with the formation of covalent bonds as fixed ropes. Furthermore, activated samples of NUC-11 displayed a good catalytic performance for the chemical synthesis of carbonates from related epoxides and CO2 with high conversion rate. Moreover, by employing NUC-11 as a catalyst, a simulator of mustard gas, 2-chloroethyl ethyl sulfide, could be quickly and efficiently oxidized into low-toxicity products of oxidized sulfoxide (CEESO). Thus, this study offers a brand new view for the design and synthesis of functional-units-modified porous MOFs, which could be potentially applied as an excellent candidate in the growing field of efficient catalysis.

6s-3d {Ba3Zn4}-Organic Framework as an Effective Heterogeneous Catalyst for Chemical Fixation of CO2 and Knoevenagel Condensation Reaction.

The exquisite combination of Ba2+ and Zn2+ with the aid of 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (H6TDP) under the condition of solvothermal self-assembly generates one highly robust [Ba3Zn4(CO2)12(HCO2)2(OH2)2]-organic framework of {[Ba3Zn4(TDP)2(HCO2)2(OH2)2]·7DMF·4H2O}n (NUC-27), in which adjacent 2D layers are interlaced via hydrogen-bonding interactions to form a 3D skeleton with peapod-like channels and nano-caged voids. It is worth emphasizing that both Ba2+ and Zn2+ ions in NUC-27 display the extremely low coordination modes: hexa-coordinated [Ba(1)] and tetra-coordinated [Ba(2), Zn(1), and Zn(2)]. Furthermore, to the best our knowledge, NUC-27 is one scarcely reported 2D-based nanomaterial with an unprecedented Z-shaped hepta-nuclear heterometallic cluster of [Ba3Zn4(CO2)12(HCO2)2(OH2)2] as SBUs, which not only has plentiful low-coordinated open metal sites but also has the excellent physicochemical properties including omni-directional opening pores, ultrahigh porosity, larger specific surface area, and the coexistence of Lewis acid-base sites. Just as expected, thanks to its rich active metal sites and pyridine groups as strong Lewis acid-base roles, completely activated NUC-27 displays high catalytic efficiency on the chemical transformation of epoxides with CO2 into cyclic carbonates under mild conditions and effectively accelerates the reaction process of Knoevenagel condensation.

Robust Heterometallic CoIILaIII2-Organic Framework for the Highly Efficient Separation of Acetylene from Light Hydrocarbon Mixtures.

A highly robust heterometallic CoIILaIII2-organic framework (NUC-19) is synthesized and features 1D rectangle-like channels with a window size of 3.4 × 6.3 Å2 and a carboxyl-group-modified inner surface. NUC-19 exhibits significantly differential uptake for C2H2, C2H4, and CH4, and the ideal adsorbed solution theory selectivities of C2H2/C2H4 (1:99, v/v) and C2H2/CH4 (50:50, v/v) at room temperature can reach up to 4.0 and 79.7, respectively. Fixed-bed dynamic breakthrough experiments under simulated industrial conditions indicate that NUC-19 could efficiently trap C2H2 from mixed gases of C2H2/CH4 and C2H2/C2H4.

One Robust Microporous TmIII-Organic Framework for Highly Catalytic Activity on Chemical CO2 Fixation and Knoevenagel Condensation.

In terms of documented references, multifunctional MOFs with high catalytic performance could be constructed from the combination of metal cations and polycarboxyl-pyridine ligands, which could efficiently endow crystallized porous frameworks with the coexisting Lewis acid-base properties. Thus, by employing a ligand-directed synthetic strategy, the exquisite combination of wave-like inorganic chains of [Tm(CO2)3(OH2)]n and mononuclear units of [Tm(CO2)4(OH2)2] with the aid of the specially designed ligand of 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H5BDCP) generates one highly robust microporous framework of {(Me2NH2)[Tm3(BDCP)2)(H2O)3]·4DMF·H2O}n (simplified as NUC-25), which contains near-rectangular nanochannels and large solvent-residing voids. Furthermore, the activated state of NUC-25 with the removal of associated water molecules is a rarely reported bifunctional heterogeneous catalyst due to the coexistence of Lewis acid-base sites including 6-coordinated Tm3+ ions, uncoordinated carboxyl oxygen atoms, and Npyridine atoms. Just as expected, NUC-25 exhibits greatly high catalytic activity for the cycloaddition reaction of epoxides with CO2 into alkyl cyclic carbonates under bland solvent-free conditions, which should be ascribed to the polarity of nitrogen-containing pyridine heterocycles as Lewis base sites on the inner surface of nano-caged voids except for recognized Lewis acid sites of rare earth cations. Moreover, the excellent pore-size-dependent catalytic property for Knoevenagel condensation reactions confirms that NUC-25 can be viewed as a recyclable bifunctional heterogeneous catalyst. Therefore, these results strongly demonstrate that microporous MOFs assembled from pre-designed polycarboxyl-heterocyclic ligands display better catalytic performance not only for chemical CO2 fixation but also for Knoevenagel condensation reactions.

Nanochannel-based heterometallic {ZnIIHoIII}-organic framework with high catalytic activity for the chemical fixation of CO2.

The exquisite combination of ZnII and HoIII generated the highly robust [ZnHo(CO2)6(OH2)]-based heterometallic framework of {[ZnHo(TDP)(H2O)]·5H2O·3DMF} n (NUC-30, H6TDP = 2,4,6-tri(2',4'-dicarboxyphenyl)pyridine), which featured outstanding physicochemical properties, including honeycomb nanochannels, high porosity, large specific surface area, the coexistence of highly open Lewis acid-base sites, good thermal and chemical stability, and resistance to most organic solvents. Due to its extremely unsaturated metal tetra-coordinated Zn(ii) ions, hepta-coordinated Ho(iii) and high faveolate void volume (61.3%), the conversion rate of styrene oxide and CO2 into cyclic carbonates in the presence of 2 mol% activated NUC-30 and 5 mol% n-Bu4NBr reached 99% under the mild conditions of 1.0 MPa and 60 °C. Furthermore, the luminescence sensing experiments proved that NUC-30 could be used as a fast, sensitive and highly efficiency sensor for the detection of Fe3+ in aqueous solution. Therefore, these results prove that nanoporous MOFs assembled from pyridine-containing polycarboxylate ligands have wide applications, such as catalysis and as luminescent materials.