Search

A novel 3D porphyrin-based COF, with 2-fold interpenetrated stp topology and greatly enhanced electrocatalytic OER performance after post-metallization, was synthesized.

A novel fluorine-functionalized 2D covalent organic framework, with kgd topology and improved C2H2/CO2 separation over its fluorine-free counterpart, is reported.

As a highly promising candidate for hydrogen storage, crucial to vehicles powered by fuel cells, metal–organic frameworks (MOFs) have attracted the attention of chemists in recent decades. H2 uptak...

The unique structural advantage of metal-organic frameworks (MOFs) determines the great prospect and developability in gas adsorption and separation. Both ligand design and microporous engineering based on crystal structure are significant lever for coping with new application exploration and requirements. Focusing on the designable pore and modifiable frameworks of MOFs, this review discussed the recent advances in the field of gas adsorption and separation, and analyzed the host-guest interaction, structure-performance relations, and the adsorption/separation mechanism from ligand design, skeleton optimization, metal node regulation, and active sites construction. Based on the function-oriented perspective, we summarized the main research recently, and made an outlook based on the focus of microporous MOFs that require further attention in the structure design and industrial application.

A Co-doping core–shell shaped NiSe2 based catalyst (NixCo1−xSe2@NC) exhibits promising electrocatalytic activity for HER with a low overpotential of −143 mV at −10 mA cm−2, a small Tafel slope of 37.5 mV dec−1.

A Ni-MOF is used as a precursor to synthesize a NiSe2/NiS2@NC heterojunction with rich phase interfaces through a selenization/sulfurization process. Overpotentials of 188 mV and 211 mV are achieved in acidic and alkaline media at 10 mA cm−2.

Accurately controlling the distance between Fe atoms can enhance the electrocatalytic activity for carbon dioxide reduction and promote the C–C coupling process, thus promoting the production of ethanol.

We present a controlled fabrication of selective ultrathin metal–organic framework (MOF) nanosheets as preassembling platforms, yolk–shell structured with a few-layered N-doped carbon (NC) shell-en...

Molybdenum diselenide (MoSe2) has been considered as promising electrocatalysts for catalyzing the hydrogen evolution reaction (HER) due to its narrow band gap and appropriate adsorption free energy. However, its catalytic performance is still impeded by inferior electrical conductivity and insufficient active sites, thus leading to unsatisfactory HER performance. Herein, MoSe2@N-doped carbon (NC) hollow nanoflowers with interfacial Mo-N-C bonds were controllably fabricated through the in situ selenization of the self-polymerized Mo-polydopamine precursor. Benefiting from the unique hollow structure, NC protective layer, and intimate interfacial interaction, the optimal MoSe2@NC displays good HER performance with low overpotentials (175 and 183 mV) and long-term stability (up to 12 h at -10 mA cm-2) in 0.5 M H2SO4 and 1.0 M KOH solutions, respectively. The theoretical results show that Mo-N-C bonds at the interface of MoSe2@NC give rise to relatively low unoccupied eg orbital density of states and ideal H2 adsorption free energy. This work presented here highlights the critical role of interfacial chemical bonds in regulating the electronic structure of nanomaterials and further improving the HER performance.

Three novel porous transition-metal-organic frameworks (TM-OFs), formulated as [Co

Exposure to ammonia (NH

An unexpected in-situ hydrolysis reaction occurred during the solvothermal reaction of N,N′-bis(4-carboxy-2-methylphenyl)pyromellitic di-imide) and Ba(NO3)2, and a novel porous Ba-MOF, [H2N(CH3)​2]0.5[Ba1.5(L)(DMA)]·1.5DMA·1.5H2O (UPC-70, H3L = 2-(4-carboxy-2-methylphenyl)-1,3-dioxoisoindoline-5,6-dicarboxylic acid, DMA = N,N-dimethylacetamide), was obtained on the basis of the partial hydrolysate. The as-synthesized 3D network with 1D open channels of different sizes (24 A and 10 A) contains abundant open metal sites after removal of solvents, which is conducive to the preferential adsorption of CO2. The subsequent gas sorption measurement reveals the high separation selectivity of UPC-70 for CO2/CH4 (15) and CO2/N2 (32) at ambient conditions, and GCMC theoretical simulation provides good verification of the experimental results, indicating that UPC-70 is a potential candidate for CO2 capture from flue gas and natural gas.

The evolution of cost-effective hydrogen evolution reaction (HER) electrocatalysts is of great significance for the development of clean energy. Exploring effective synthesis strategies to optimize the performance of non-noble metal electrocatalysts has always attracted our attention. Herein, ultrathin coordination polymers were used as precursors to controllably synthesize two-dimensional (2D) ultrathin dual-phase transition metal selenide (TMSs)/carbon–nitrogen (CN) composites (CoSe2–NiSe2/CN) by a two-step method (first a low temperature hydrothermal method for selenization, and then high temperature calcination selenization). Benefiting from its large specific surface area (49 m2 g−1), abundant catalytically active sites and synergistic effects, CoSe2–NiSe2/CN can significantly enhance the HER catalytic activity and exhibits good electrocatalytic activity with an overpotential of 150 mV at −10 mA cm−2, and a small Tafel slope of 42 mV dec−1 in an acidic electrolyte for the HER. This work provides a new strategy for optimizing the HER catalytic activity of TMSs by preparing 2D ultrathin dual-phase TMS composite materials.

The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with T

Iron, N-codoped carbon materials (Fe-N-C) are promising electrocatalysts toward oxygen reduction reactions due to their high atom utilization efficiency and intrinsic activity. Nanostructuring of the Fe-N-C materials, such as introducing porosity into the carbon structure, would be conducive to further increasing the exposure of active sites as well as improving the mass transfer. Herein, we explore the potential of iron complex-functionalized micelles of mesoporous SiO

Solid-state transformations in metal-organic framework (MOF) systems are important phenomena and have led to the creation of new MOF structures. Solid-state transformations from interpenetrated to non-interpenetrated networks involving rearrangement of secondary building units (SBUs) in a single-crystal-to-single-crystal (SCSC) fashion have not been explored to date. Herein, we report the sequential, thermally stimulated solid-state transformations in a barium-organic framework ( UPC-600 ). The two-fold interpenetrated framework of UPC-600 is converted at 373 K to UPC-601 , a non-interpenetrated framework. This proceeds in a SCSC fashion and involves the rearrangement of two proximate rod-shaped SBUs in different nets to generate a new rod-shaped SBU. At 473 K, a continuous solid-state transformation involving a second rearrangement occurred, UPC-601 converted to UPC-602 by the rearrangement of the 1D rod-shaped SBU to a 2D layer SBU. This is the first example of such a thermally-driven stepwise transformation involving simultaneous cleavage and regeneration of multiple bonds. This result will enable detailed studies of solid-state transformations, and encourages a deep understanding of the role of solid-state transformations in the synthesis of MOF materials.

The design of MOFs with functionalized groups as well as suitable pore space plays a momentous part in gas adsorption and separation. Herein, a new Zn-MOF (Zn4(BTB-NH2)3·xsolvent, UPC-98, H3BTB-NH2...

Facile preparation of cost-effective and durable porous carbon-supported non-precious-metal/nitrogen electrocatalysts for oxygen reduction reaction (ORR) is extremely important for promoting the commercialized applications of such catalysts. In this work, the FeCl3-containing porphyrinato iron-based covalent porous polymer (FeCl3·FePor-CPP) was fabricated in-situ onto porous corncob biomass supports via a simple one-pot method. Subsequent thermal-reduction pyrolysis at 700 °C–900 °C with CO2 gas as an activating agent resulted in Fe2O3-decorated and N-doped graphitic carbon composite Fe2O3@NCb NC = N-doped graphene analog; bio-C = the corncob-derived hierarchically porous graphitic biomass carbon framework). The derived α-Fe2O3 and γ-Fe2O3 nanocrystals (5–10 nm particle diameter) were all immobilized on the N-doped bio-C micro/nanofibers. Notably, the Fe2O3@NC&bio-C obtained at the pyrolysis temperature of 800 °C (Fe2O3@NC&bio-C-800), exhibited unusual ORR catalytic efficiency via a 4-electron pathway with the onset and half-wave potentials of 0.96 V and 0.85 V vs. RHE, respectively. In addition, Fe2O3@NC&bio-C-800 also exhibited a high and stable limiting current density of -6.0 mA cm−2, remarkably stability (larger than 91% retention after 10000s), and good methanol tolerance. The present work represents one of the best results for iron-based biomass material ORR catalysts reported to date. The high ORR activity is attributed to the uniformly distributed α-Fe2O3 and γ-Fe2O3 nanoparticles on the N-enriched carbon matrix with a large specific surface area of 772.6 m2 g−1. This facilitates favor faster electron movement and better adsorption of oxygen molecules on the surface of the catalyst. Nevertheless, comparative studies on the structure and ORR catalytic activity of Fe2O3@NC&bio-C-800 with Fe2O3@bio-C-800 and NC&bio-C-800 clearly highlight the synergistic effect of the coexisting Fe2O3 nanocrystals, NC, and bio-C on the ORR performance.

Facile design of economic-effective hydrogen evolution reaction (HER) catalysts with non-noble materials are promising for the production of renewable chemical fuels. Two-dimensional (2D) ultrathin transition metal dichalcogenides (TMDs) materials with large specific surface area and abundant catalytic active sites can significantly enhance their catalytic activities. Herein, we design and synthesize an atomically thin Ni-Se-S based hybrid nanosheet (NiSe1.2S0.8) via a simple solvothermal method, the thickness of NiSe1.2S0.8 nanosheets is only about 1.1 nm. Benefiting from the ultrathin nanostructure and rich defects, the optimal NiSe1.2S0.8 exhibits good electrocatalytic activity with the overpotential of 144 mV at −10 mA·cm−2, a small Tafel slope of 59 mV·dec−1, and outstanding catalytic stability in acid electrolyte for HER. The theoretical results show that hybrid electrocatalyst by S incorporation possesses the optimal adsorption free energy of hydrogen (ΔGH*). This study provides a simple method to synthesize a highperformance multicomponent electrocatalysts with the ultrathin nanostructures and abundant defects.

Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) promises a practical way to produce high-purity C2H2 required for industrial applications. However, challenges exist in the pore environment engineering of porous materials to recognize two molecules due to their similar molecular sizes and physical properties. Herein, we report a strategy to optimize pore environments of multivariate metal-organic frameworks (MOFs) for efficient C2H2/CO2 separation by tuning metal components, functionalized linkers, and terminal ligands. The optimized material UPC-200(Al)-F-BIM, constructed from Al3+ clusters, fluorine-functionalized organic linkers, and benzimidazole terminal ligands, demonstrated the highest separation efficiency (C2H2/CO2 uptake ratio of 2.6) and highest C2H2 productivity among UPC-200 systems. Experimental and computational studies revealed the contribution of small pore size and polar functional groups on the C2H2/CO2 selectivity and indicated the practical C2H2/CO2 separation of UPC-200(Al)-F-BIM.

A series of isostructural rare-earth metal–organic frameworks (RE-MOFs), namely {[RE(L-X)(H2O)]·2DMF}n (UPC-38, RE = Eu, Tb, X = H, F, Cl, NH2, CH3, OCH3; L = [1,1′:3′,1′′-terphenyl]-4,4′′,5′-tricarboxylic acid) have been successfully synthesized under solvothermal conditions. Single-crystal X-ray diffraction analysis shows that UPC-38 is an unprecedented three-dimensional (3D) (3,4,5)-czkf topological framework with one-dimensional (1D) chain secondary building units. Different functional groups can be attached to the ligand (L), and the effects of the different functional groups on the fluorescence intensity, emission wavelength and quantum yield of UPC-38 were systematically studied. It was found that the introduction of an amino group causes the emission wavelength to red shift significantly, while that of other groups causes slight effects on the emission wavelengths. UPC-38(Eu)-H and UPC-38(Tb)-H without modified functional groups in these twelve crystals exhibit the highest quantum yield ratios of 16.64% and 28.06%, respectively. Remarkably, by adjusting the ratio of Eu3+ to Tb3+ and the L-OCH33+ ligand with the strongest blue emission, a series of double-doped rare-earth metal–organic frameworks, UPC-38(EuxTb1−x)-OCH3 (0 ≤ x ≤ 1), are successfully acquired. The calculated CIE coordinates of UPC-38(Eu)-OCH3 and UPC-38(Tb)-OCH3 are (0.50, 0.28) and (0.23, 0.45), respectively. It is exciting that a white light emitting material, UPC-38(Eu0.34Tb0.66)-OCH3, can be successfully obtained through careful tuning of the Eu3+/Tb3+ ratio in the framework. The CIE coordinate is (0.335, 0.325), which is very close to the standardized value of (0.333, 0.333).

Two series of lanthanide-based metal–organic frameworks, namely {[Ln(BIPA-TC)0.5(DMA)2(NO3)]·DMA·H2O}n (1-Ln, Ln = Eu, Dy, Sm, Nd) and {[Ln2(BIPA-TC)1.5(DMA)3(H2O)2]·2DMA·2H2O}n (2-Ln, Ln = Eu, Dy, Sm, Nd), were successfully constructed via a solvent regulation strategy based on a π-electron rich tetra-carboxylate ligand (H4BIPA-TC). 1-Ln shows a 4-connected lvt topology with the point symbol of {42·84}, but 2-Ln displays a new 4,4,6-connected wxk1 topology with the point symbol of {43·83}4{46·66·83}2{86}. The solid-state luminescence property and the microporous nature of Eu-MOFs (1-Eu and 2-Eu) indicate that they can potentially be used as luminescent sensors. Fluorescence measurements indicate that Fe3+ exhibits the quenching effect for 1-Eu with the quenching efficiency of 93.1%. 2-Eu is the first MOF sensor for Mg2+ with the lowest detection limit of 1.53 × 10−10 mol L−1 and displays good recyclable capability. Simultaneously, in the presence of other metal ions (Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pd2+, Al3+, Cr3+and Fe3+), 2-Eu can maintain the selective sensing of Mg2+, indicating its potential for Mg2+ turn-on sensing.

A series of cobalt and metal-free phthalocyanine ambipolar semiconductors, MPc[β/α-O(4-CF3-Ph)4] (M = Co, 2H) (1–4), are synthesized and fabricated into self-assembled microstructures. The Co[Pc(β/α-OPhCF3)4] (1 and 3) molecules formed one-dimensional (1D) nanoribbons (400–300 nm) with a larger width of 1 relative to 3, whereas the H2Pc[β/α-O(4-CF3-Ph)4] (2 and 4) molecules self-assembled into wider microbelts (5–4 μm) with 2 larger than 4, showing the effect of the M center and the substituent positions of the Pc rings on the dimensions of the microstructures. An increased crystallinity is revealed in the order of 4 < 3 < 2 < 1, resulting in an increased conductivity in the same order. Towards NO2 and NH3, both positive and negative current changes are found among the sensors 1–4, with the lowest limit of detection (LOD) as low as 3 ppb for NO2 and 420 ppb for NH3 from 1, while a positive current response to H2S is obtained only from 1 with a LOD of 100 ppb, respectively, achieving the best results for the room-temperature detection of NO2, NH3 and H2S gases based on all of the solution-processed phthalocyanine-based sensors reported so far. Accordingly, the sensor responses are dominated by both M-analyst interaction (M = Co, 2H) and conductivity among the sensors 1–4. In particular, different sensor arrays consisting of the sensor of 1 combined with one of the other three sensors of 2–4 are established. NO2, NH3 and H2S gases at ppb levels can be accurately identified by the combination of two parameters, namely current change direction and sensitivity.

Eight new stable porous lanthanide metal-organic frameworks (Ln-OFs), namely, [Ln

The selective adsorption of APPT-Cd-MOF 1 for propyne, 2-butyne and phenylacetylene was confirmed by single-crystal analysis. In addition, the selective adsorption performance of Cd-MOF for C3H4/C3H6/C3H8 was investigated. The matching of the functionality and size/shape between porous materials and guest molecules clarified the specific recognition of 1 for linear alkyne molecules.

Molybdenum diselenide (MoSe

The evolution of cost-effective hydrogen evolution reaction (HER) electrocatalysts is of great significance for the development of clean energy. Exploring effective synthesis strategies to optimize the performance of non-noble metal electrocatalysts has always attracted our attention. Herein, ultrathin coordination polymers were used as precursors to controllably synthesize two-dimensional (2D) ultrathin dual-phase transition metal selenide (TMSs)/carbon-nitrogen (CN) composites (CoSe2-NiSe2/CN) by a two-step method (first a low temperature hydrothermal method for selenization, and then high temperature calcination selenization). Benefiting from its large specific surface area (49 m2 g-1), abundant catalytically active sites and synergistic effects, CoSe2-NiSe2/CN can significantly enhance the HER catalytic activity and exhibits good electrocatalytic activity with an overpotential of 150 mV at -10 mA cm-2, and a small Tafel slope of 42 mV dec-1 in an acidic electrolyte for the HER. This work provides a new strategy for optimizing the HER catalytic activity of TMSs by preparing 2D ultrathin dual-phase TMS composite materials.

Covalent organic frameworks (COFs), a fast-growing field in crystalline porous materials, have achieved tremendous success in structure development and application exploration over the past decade. The vast majority of COFs reported to date are designed according to the basic concept of reticular chemistry, which is rooted in the idea that building blocks are fully connected within the frameworks. We demonstrate here that sub-stoichiometric construction of 2D/3D COFs can be accomplished by the condensation of a hexagonal linker with 4-connected building units. It is worth noting that the partially connected frameworks were successfully reticulated for 3D COFs for the first time, representing the highest BET surface area among imine-linked 3D COFs to data. The unreacted benzaldehydes in COF frameworks can enhance C2H2 and CO2 adsorption capacity and selectivities between C2H2/CH4 and C2H2/CO2 for sub-stoichiometric 2D COFs, while the reserved benzaldehydes control the interpenetrated architectures for the 3D case, achieving a rare non-interpenetrated pts topology for 3D COFs. This work not only paves a new avenue to build new COFs and endows residual function groups with further applications but also prompts redetermination of reticular frameworks in highly connected and symmetrical COFs.

As a clean and promising hydrogen production process, the electrochemical hydrogen evolution reaction (HER) is particularly important. However, its electrocatalytic activity is usually limited by t...

Linker desymmetrization has been witnessed as a powerful design strategy for the discovery of highly connected metal-organic frameworks (MOFs) with unprecedented topologies. Herein, we introduce molecular pivot-hinge installation as a linker desymmetrization strategy to evolve the topology of highly connected rare-earth (RE) MOFs, where a pivot group is placed in the center of a linker similar to a hinge. By tuning the composition of pivot groups and steric hindrances of the substituents on various linker rotamers, MOFs with various topologies can be obtained. The combination of L-SO2 with C2v symmetry and 12-connected RE9 clusters leads to the formation of a fascinating (4,12)-c dfs new topology. Interestingly, when replacing L-SO2 with a tetrahedra linker L-O, the stacking behaviors of RE-organic layers switch from an eclipsed mode to a staggered stacking mode, leading to the discovery of an intriguing hjz topology. Additionally, the combination of the RE cluster and a linker [(L-(CH3 )6 )] with more bulky groups gives rise to a flu topology with a new 8-c inorganic cluster. The diversity of these RE-MOFs was further enhanced through post-synthetic installation of linkers with various functional groups. Functionalization of each linker with acidic and basic units in the mesoporous RE-based PCN-905-SO2 allows for efficient cascade catalytic transformation within the functionalized channels.

Two Co(II)-MOFs with different structures were successfully synthesized under the premise of designing two ligands containing alkynyl functional groups. Complexes 1 ([Co(TEPA)(TPT)2/3]·2DMF·H2O) and 2 ([Co(EPA)(TPT)]·1.5DMF·1.5H2O) show excellent luminescence properties. Meanwhile, as fluorescent sensors, complexes 1 and 2 exhibit selectivity and sensitivity for Fe3+ with the Ksv of 1.520 × 104 L/mol and 3.543 × 104 L/mol, which can rapidly detect nitroaromatic compounds in methanol and ethanol, especially for 2,4-NPH through fluorescence quenching with high quenching efficiency. In particular, the Ksv value of complexes 1 and 2 towards 2,4-NPH can reach up to 1.627 × 105 L/mol and 9.600 × 104 L/mol, demonstrating that complexes 1 and 2 are good candidates for the identification and detection of Fe3+ and nitroaromatic compounds.

Ethylene (C2H4) and propylene (C3H6) are important energy sources and raw materials in the chemical industry. Storage and separation of C2H4 and C3H6 are vital to their practical application. Metal–organic frameworks (MOFs) having adjustable structures and pore environments are promising candidates for C3H6/C2H4 separation. Herein, we obtained a Cu-based MOF synthesized by H3TTCA and pyrazine ligands. By adding different functional groups on the ligands within the MOFs, their pore environments are adjusted, and thus, the C3H6 storage capacity and C3H6/C2H4 separation efficiency are improved. Eventually, the fluoro- and methyl-functionalized iso-MOF-4 exhibits a better gas storage and C3H6/C2H4 separation performance compared with iso-MOF-1 (nonfunctionalized), iso-MOF-2 (fluoro-functionalized), and iso-MOF-3 (methyl-functionalized). A record-high C3H6 uptake of 293.6 ± 2.3 cm3 g–1 (273 K, 1 atm) is achieved using iso-MOF-4. Moreover, iso-MOF-4 shows excellent repeatability, and only 3.5% of C3H6 storage capacities decrease after nine cycles. Employing Grand Canonical Monte Carlo (GCMC) simulations, it is indicated that iso-MOF-4 preferentially adsorbs C3H6 rather than C2H4 at low pressure. Single-crystal X-ray diffraction on C3H6-adsorbed iso-MOF-4 crystals precisely demonstrates the adsorption positions and arrangement of C3H6 molecules in the framework, which is consistent with the theoretical simulations. Remarkably, gas sorption isotherms, molecular simulations, and breakthrough experiments comprehensively demonstrate that this unique MOF material exhibits highly efficient C3H6/C2H4 separation. Additionally, iso-MOF-4 also possesses efficient separation of C3H8/CH4 and C2H6/CH4, indicating its promising potential in storage/separation of light hydrocarbons in industry., Fine-tuning the pore environment through multifunctionalized ligand modification in an isoreticular Cu-MOF framework for optimal gas adsorption and separation is studied.

Pseudomorphic conversion of metal-organic frameworks (MOFs) enables the fabrication of nanomaterials with well-defined porosities and morphologies for enhanced performances. However, the commonly reported calcination strategy usually requires high temperature to pyrolyze MOF particles and often results in uncontrolled growth of nanomaterials. Herein, we report the controlled alkaline hydrolysis of MOFs to produce layered double hydroxide (LDH) while maintaining the porosity and morphology of MOF particles. The preformed trinuclear M3(μ3-OH) (M = Ni2+ and Co2+) clusters in MOFs were demonstrated to be critical for the pseudomorphic transformation process. An isotopic tracing experiment revealed that the 18O-labeled M3(μ3-18OH) participated in the structural assembly of LDH, which avoided the leaching of metal cations and the subsequent uncontrolled growth of hydroxides. The resulting LDHs maintain the spherical morphology of MOF templates and possess a hierarchical porous structure with high surface area (BET surface area up to 201 m2·g-1), which is suitable for supercapacitor applications. As supercapacitor electrodes, the optimized LDH with the Ni:Co molar ratio of 7:3 shows a high specific capacitance (1652 F·g-1 at 1 A·g-1) and decent cycling performance, retaining almost 100% after 2000 cycles. Furthermore, the hydrolysis method allows the recycling of organic ligands and large-scale synthesis of LDH materials.

The structural diversity of highly connected metal-organic frameworks (MOFs) has long been limited due to the scarcity of highly connected metal clusters and the corresponding available topology. Herein, we deliberately chose a series of tritopic linkers with multiple substituents to construct a series of highly connected rare-earth (RE) MOFs. The steric hindrance of these substituents can be systematically tuned to generate various linker rotamers with tunable configurations and symmetries. For example, the methyl-functionalized linker (L-CH3) with C2 v symmetry exhibits larger steric hindrance, forcing two peripheral phenyl rings perpendicular to the central one. The combination of C2 v linkers and 9-connected RE6 clusters leads to the formation of a new fascinating (3,9)-c sep topology. Unlike Zr-MOFs exhibiting Zr6 clusters in various linker configurations and corresponding different structures, the adaptable RE6 clusters can undergo metal insertion and rearrange into new RE9 clusters when connected to an unfunctionalized linker (L-H) with C1 symmetry, giving rise to a new (3,3,18)-c ytw topology. More interestingly, by judiciously combining the linkers with both small and bulky substituents through mixed-linker strategies, an RE9-based MOF with an engaging (3,3,12)-c flg topology could be obtained as a result of continuous steric hindrance control. In this case, the two mixed linkers adopt configurations with moderate steric hindrances. Molecular simulation demonstrates that the combination of substituents with various steric hindrances dictates the resulting MOF structures. This work provides insights into the discovery of unprecedented topologies through systematic and continuous steric tuning, which can further serve as a blueprint for the design and construction of highly complicated porous structures for sophisticated applications.

Three cadmium(II) metal-organic frameworks (MOFs) based on tetracarboxylate ligands, namely [Cd2(TTTA)(DMF)3]·2DMF (1), [Cd2(TB)(H2O)4]·3DMF·H2O (2) and [Cd(TEB)0.5]·2DMF·4H2O (3) have been designed and synthesized. Complex 1 is a 2-dimensional (2D) 3,4-connected network with 3,4L13 topology, complex 2 features a 3-dimensional (3D) 3,4-connected tfa topology with a 2-fold interpenetrating structure and complex 3 has a 3D 4-connected dia topology with a 4-fold interpenetrating structure. Interestingly, 2 exhibits permanent pores and selective adsorption of CO2 over CH4. In addition, 2 shows fluorescence sensing of Fe3+ ion and rapid detection of nitroaromatic compounds (NACs) through fluorescence quenching.

A 3D microporous MOF [Cu1.5(BTB-NH2)(H2O)2]·6DMA·5H2O (UPC-99) of the (2,3,4-c)-net novel topology type was successfully constructed by the amino-functionalized ligand and Cu(II) ions via a solvothermal method. Due to the presence of two channels with open Cu(II) sites and –NH2 groups, UPC-99 exhibits a high adsorption selectivity of 15.3 for CO2/CH4 at 1 bar and 273 K. Remarkably, UPC-99 exhibits a significant adsorption difference in C3H6 and C3H8 relative to CH4 and shows a high separation selectivity for C3 light hydrocarbons relative to CH4 (496.7 for C3H6/CH4 and 410.5 for C3H8/CH4 at 273 K, 1 bar) by single-component gas sorption and selectivity calculations in IAST methods. Moreover, the presence of open Lewis acidic Cu(II) sites in the channels allows UPC-99 to exhibit excellent catalytic performance in the catalytic cycloaddition reactions of CO2 with epoxides.