Pore Space Partition by Symmetry-Matching Regulated Ligand Insertion and Dramatic Tuning on Carbon Dioxide Uptake

Multi-Stage Optimization of Pore Size and Shape in Pore-Space-Partitioned Metal-Organic Frameworks for Highly Selective and Sensitive Benzene Capture

Compared to exploratory development of new structure types, pushing the limits of isoreticular synthesis on a high-performance MOF platform may have higher probability of achieving targeted properties. Multi-modular MOF platforms could offer even more opportunities by expanding the scope of isoreticular chemistry. However, navigating isoreticular chemistry towards best properties on a multi-modular platform is challenging due to multiple interconnected pathways. Here on the multi-modular pacs (partitioned acs) platform, we demonstrate accessibility to a new regime of pore geometry using two independently adjustable modules (framework-forming module 1 and pore-partitioning module 2). A series of new pacs materials have been made. Benzene/cyclohexane selectivity is tuned, progressively, from 4.5 to 15.6 to 195.4 and to 482.5 by pushing the boundary of the pacs platform towards the smallest modules known so far. The exceptional stability of these materials in retaining both porosity and single crystallinity enables single-crystal diffraction studies of different crystal forms (as-synthesized, activated, guest-loaded) that help reveal the mechanistic aspects of adsorption in pacs materials.

Exploring the Fluorination and Hydroxylation of Pore-Space-Partitioned Metal-Organic Frameworks for C2H2/CH4 Separation

We report three novel pore-space-partitioned metal-organic frameworks (MOFs) functionalized with fluorine and hydroxyl groups using 2,3,5,6-tetrafluorobenzene-1,4-dicarboxylic acid (F4-BDC) and a new ligand 3,6-difluoro-2,5-dihydroxybenzene-1,4-dicarboxylic acid (F2(OH)2-BDC) as organic building blocks, with 1,3,5-tris(4-pyridyl)-2,4,6-triazine (TPT) as pore partition agent. With the polar fluorine and hydroxyl groups and the open metal sites being blocked by TPT, moderate molecule-framework interactions can be engineered. These three isoreticular microporous frameworks Mn-TPT-BDC-F4 (NCKU-21), Mn-TPT-BDC-F2(OH)2 (NCKU-22), and Mg-TPT-BDC-F2(OH)2 (NCKU-23) (NCKU=National Cheng Kung University) exhibit distinct single-component gas adsorption behaviors. Although NCKU-22 uptakes a much lower amount of C2H2 compared to NCKU-21 and -23, dynamic breakthrough experiments show that these three materials are all capable of efficient C2H2/CH4 separations. These MOFs possess moderate isosteric heat of adsorption for C2H2 (25.7-32.1 kJ mol-1), allowing easy regeneration and energy-efficient C2H2/CH4 separations.

Mechanochemical "Cage-on-MOF" Strategy for Enhancing Gas Adsorption and Separation through Aperture Matching

Post-modification of porous materials with molecular modulators has emerged as a well-established strategy for improving gas adsorption and separation. However, a notable challenge lies in maintaining porosity and the limited applicability of the current method. In this study, we employed the mechanochemical "Cage-on-MOF" strategy, utilizing porous coordination cages (PCCs) with intrinsic pores and apertures as surface modulators to improve the gas adsorption and separation properties of the parent MOFs. We demonstrated the fast and facile preparation of 28 distinct MOF@PCC composites by combining 7 MOFs with 4 PCCs with varying aperture sizes and exposed functional groups through a mechanochemical reaction in 5 mins. Only the combinations of PCCs and MOFs with closely matched aperture sizes exhibited enhanced gas adsorption and separation performance. Specifically, MOF-808@PCC-4 exhibited a significantly increased C2H2 uptake (+64 %) and a longer CO2/C2H2 separation retention time (+40 %). MIL-101@PCC-4 achieved a substantial C2H2 adsorption capacity of 6.11 mmol/g. This work not only highlights the broad applicability of the mechanochemical "Cage-on-MOF" strategy for the functionalization of a wide range of MOFs but also establishes potential design principles for the development of hybrid porous materials with enhanced gas adsorption and separation capabilities, along with promising applications in catalysis and intracellular delivery.

A Scalable Pore-space-partitioned Metal-organic Framework Powered by Polycatenation Strategy for Efficient Acetylene Purification

Efficient separation of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4) is a significant challenge in the petrochemical industry due to their similar physicochemical properties. Pore space partition (PSP) has shown promise in enhancing gas adsorption capacity and selectivity by reducing pore size and increasing the density of guest binding sites. Herein, we firstly employ the 2D→3D polycatenation strategy to construct a PSP metal-organic framework (MOF) Ni-dcpp-bpy, incorporating functional N/O sites to enhance C2H2 purification. The polycatenated framework with optimized pore size and regularity, exhibiting significant improvements over traditional PSP MOFs by resolving the critical contradiction of balancing C2H2 uptake (98.5 cm3 g-1 at 298 K, 100 kPa) and selectivity of C2H2/CO2 (3.4), C2H2/C2H4 (5.9), and C2H2/CH4 (96.4) in a MOF. Breakthrough experiments confirm high-purity C2H4 (>99.9 %) and high C2H2 productivity from binary and ternary mixtures. Notably, Ni-dcpp-bpy exhibits excellent water stability, scalability, and regenerability after 20 cycles for separating C2H2/CO2. Theoretical calculations verify that the strong binding of C2H2 is mainly attributed to the C-H⋅⋅⋅O/N interactions between host Ni-dcpp-bpy and guest C2H2 molecules. The polycatenation strategy not only improved industrial C2H2 purification efficiency but also enriched the design diversity of customized MOFs for other gas separation applications.

Topological Transformation and Dimensional Reduction in Multicomponent Metal-Organic Frameworks for Gas Separations

Multicomponent MOFs have offered a wide range of opportunities to harness new properties. However, the synthesis of multicomponent MOFs remains challenging. This work demonstrates the synthesis of a family of multicomponent MOFs by topological transformation from well-established multicomponent partitioned acs (pacs) structures. Such transformation is based on the new understanding on the self-assembly process of pacs MOFs. A key to this understanding is that pacs structures, topologically regarded as the introduction of a pore-partitioning ligand into MOF-235/MIL-88 type framework, are likely to be formed in a layer-pillar-layer fashion in practical reactions. As the π-π interaction between layers and other chemical interactions during the self-assembly process are recognized, the structural transformation can be modulated from 3D pacs structures to 2D interrupted pacs structures (denoted i-pacs). It is especially noteworthy that such dimensional reduction is first observed in metal-organic frameworks and the i-pacs MOFs contain four structural modules and up to five components, which have the highest complexity among 2D MOFs. Interestingly, the i-pacs MOFs have significantly enhanced performance for CO2/N2 separation in comparison with pacs MOFs.

Ligand Circuit Concept for Developing Gas Separation Materials from Pore-Space-Partitioned Metal-Organic Frameworks

Isoreticular chemistry is among the most powerful strategies for designing novel materials with optimizable pore geometry and properties. Of great significance to the further advance of isoreticular chemistry is the development of broadly applicable new concepts capable of guiding and systematizing the ligand-family expansion as well as establishing correlations between dissimilar and seemingly uncorrelated ligands for better predictive synthetic design and more insightful structure and property analysis. Here ligand circuit concept is proposed and its use has been demonstrated for the synthesis of a family of highly stable, high-performance pore-space-partitioned materials based on an acyclic ligand, trans, trans-muconic acid. This work represents a key step toward developing highly porous and highly stable pore-space-partitioned materials from acyclic ligands. The new materials exhibit excellent sorption properties such as high uptake capacity for CO2 (81.3 cm3 g-1) and C2H2 (165.4 cm3 g-1) by CPM-7.3a-NiV. CPM-7.3a-CoV shows C2H6-selective C2H6/C2H4 separation properties and its high uptakes for C2H4 (134.0 cm3 g-1) and C2H6 (148.0 cm3 g-1) at 1 bar and 298 K contribute to the separation potential of 1.35 mmol g-1. The multi-cycle breakthrough experiment confirms the promising separation performance for C2H2/CO2.

Metal-organic framework with pore contraction and modification by diethylammonium cations for record SO2/CO2 separation

A robust MOF with diethylammonium cations in its pores, enhances pore partitioning and modifies the environment, enabling selective and dense SO2 packing through hydrogen bonds. It achieves a reversible SO2 uptake with a high adsorption enthalpy and record IAST selectivity of 1182 for SO2/CO2 at 298 K and 1 bar.

Ultrastable Carboxyl-Functionalized Pore-Space-Partitioned Metal-Organic Frameworks for Gas Separation

Isoreticular chemistry, which enables property optimization by changing compositions without changing topology, is a powerful synthetic strategy. One of the biggest challenges facing isoreticular chemistry is to extend it to ligands with strongly coordinating substituent groups such as unbound -COOH, because competitive interactions between such groups and metal ions can derail isoreticular chemistry. It is even more challenging to have an isoreticular series of carboxyl-functionalized MOFs capable of encompassing chemically disparate metal ions. Here, with the simultaneous introduction of carboxyl functionalization and pore space partition, a family of carboxyl-functionalized materials is developed in diverse compositions from homometallic Cr3+ and Ni2+ to heterometallic Co2+/V3+, Ni2+/V3+, Co2+/In3+, Co2+/Ni2+. Cr-MOFs remain highly crystalline in boiling water. Unprecedentedly, one Cr-MOF can withstand the treatment cycle with 10m NaOH and 12m HCl, allowing reversible inter-conversion between unbound -COOH acid form and -COO- base form. These materials exhibit excellent sorption properties such as high uptake capacity for CO2 (100.2 cm3 g-1) and hydrocarbon gases (e.g., 142.1 cm3 g-1 for C2H2, 110.5 cm3 g-1 for C2H4) at 1 bar and 298K, high benzene/cyclohexane selectivity (up to ≈40), and promising separation performance for gas mixtures such as C2H2/CO2 and C2H2/C2H4.

Construction of Coordination Spaces with Narrow Pore Windows in Co-Based Metal-Organic Frameworks toward CO2/N2 Separation

Carbon emission reduction is an important measure to mitigate the greenhouse effect, which has become a hotspot in global climate change research. To contribute to this, here, we fabricated two Co-based metal-organic frameworks (Co-MOFs), namely, {[Co3(NTB)2(bib)]·(DMA)2·(H2O)4}n (DZU-211) and {[Co3(NTB)2(bmip)]·(DMA)2}n (DZU-212) (H3NTB = 4,4',4″-nitrilotribenzoic acid, bib = 1,4-bis(imidazol-1-yl)-butane, bmip = 1,3-bis(2-methyl-1H-imidazol-1-yl)propane) to realize efficient CO2/N2 separation by dividing coordination spaces into suitable pores with narrow windows. DZU-211 reveals a 3D open porous framework, while DZU-212 exhibits a 3D double-fold interpenetrated structure. The two MOFs both possess large coordination spaces and small open pore sizes, via the bib ligand insertion and framework interpenetration, respectively. Comparatively, DZU-211 reveals superior selective CO2 uptake properties due to its more suitable pore characteristics. Gas sorption experiments show that DZU-211 has a CO2 uptake of 52.6 cm3 g-1 with a high simulated CO2/N2 selectivity of 101.7 (298 K, 1 atm) and a moderate initial adsorption heat of 38.1 kJ mol-1. Moreover, dynamic breakthrough experiments confirm the potential application of DZU-211 as a CO2 separation material from postcombustion flue gases.

Spatially Confined π-Complexation within Pore-Space-Partitioned Metal-Organic Frameworks for Enhanced Light Hydrocarbon Separation and Purification

Ultramicroporous metal-organic frameworks (MOFs) are demonstrated to be advantageous for the separation and purification of light hydrocarbons such as C2H2, C2H4, and CH4. The introduction of transition metal sites with strong π-complexation affinity into MOFs is more effective than other adsorption sites for the selective adsorption of π-electron-rich unsaturated hydrocarbon gases from their mixtures. However, lower coordination numbers make it challenging to produce robust MOFs directly utilizing metal ions with π-coordination activity, such as Cu+, Ag+, and Pd2+. Herein, a series of novel π-complexing MOFs (SNNU-33s) with a pore size of 4.6 Å are precisely constructed by cleverly introducing symmetrically matched C3-type [Cu(pyz)3] (pyz = pyrazine) coordinated fragments into 1D hexagonal channels of MIL-88 prototype frameworks. Benifit from the spatial confinement combined with π-complex-active Cu+ of [Cu(pyz)3], pore-space-partitioned SNNU-33 MOFs all present excellent C2H2/CH4, C2H4/CH4, and CO2/CH4 separation ability. Notably, the optimized SNNU-33b adsorbent demonstrates top-level IAST selectivity values for C2H2/CH4 (597.4) and C2H4/CH4 (69.8), as well as excellent breakthrough performance. Theoretical calculations further reveal that such benchmark light hydrocarbon separation and purification ability is mainly ascribed to the extra-strong binding affinity between Cu+ and π-electron donor molecules via a spatially confined π-complexation process.

Ordered assembly of two different metal clusters with the same topological connectivity in one single coordination network

The introduction of heterogeneous components within one single coordination network leads to the multifunctionality of the final material. However, it is hard to precisely control the local distribution of these different components in such a coordination network, especially for different components with identical topological connectivity. In this study, we successfully achieved the ordered assembly of [Mn3(μ3-O)] nodes and [Mn6(μ3-O)2(CH3COO)3] nodes within one pacs coordination network. The resulting new structure (NPU-6) with heterogeneous metal nodes simultaneously inherits the advantages of both parent networks (good thermal stability and high pore volume). The significant effect of the reaction concentration of competing ligand CH3COO- on the mixed assembly of these two nodes in NPU-6 is revealed by a series of control experiments. This method is anticipated to offer a valuable reference for orderly assembling heterogeneous components in coordination networks.

Advancing Pore-Space-Partitioned Metal-Organic Frameworks with Isoreticular Cluster Concept

Trigonal planar M3(O/OH) trimers are among the most important clusters in inorganic chemistry and are the foundational features of multiple high-impact MOF platforms. Here we introduce a concept called isoreticular cluster series and demonstrate that M3(O/OH), as the first member of a supertrimer series, can be combined with a higher hierarchical member (double-deck trimer here) to advance isoreticular chemistry. We report here an isoreticular series of pore-space-partitioned MOFs called M3M6 pacs made from co-assembly between M3 single-deck trimer and M3x2 double-deck trimer. Important factors were identified on this multi-modular MOF platform to guide optimization of each module, which enables the phase selection of M3M6 pacs by overcoming the formation of previously-always-observed same-cluster phases. The new pacs materials exhibit high surface area and high uptake capacity for CO2 and small hydrocarbons, as well as selective adsorption properties relevant to separation of industrially important mixtures such as C2H2/CO2 and C2H2/C2H4. Furthermore, new M3M6 pacs materials show electrocatalytic properties with high activity.

Tailorable Multi-Modular Pore-Space-Partitioned Vanadium Metal-Organic Frameworks for Gas Separation

Currently, few porous vanadium metal-organic frameworks (V-MOFs) are known and even fewer are obtainable as single crystals, resulting in limited information on their structures and properties. Here this work demonstrates remarkable promise of V-MOFs by presenting an extensible family of V-MOFs with tailorable pore geometry and properties. The synthesis leverages inter-modular synergy on a tri-modular pore-partitioned platform. New V-MOFs show a broad range of structural features and sorption properties suitable for gas storage and separation applications for C2H2/CO2, C2H6/C2H4, and C3H8/C3H6. The c/a ratio of the hexagonal cell, a measure of pore shape, is tunable from 0.612 to 1.258. Other tunable properties include pore size from 5.0 to 10.9 Å and surface area from 820 to 2964 m2 g-1. With C2H2/CO2 selectivity from 3.3 to 11 and high uptake capacity for C2H2 from 65.2 to 182 cm3 g-1 (298K, 1 bar), an efficient separation is confirmed by breakthrough experiments. The near-record high uptake for C2H6 (166.8 cm3 g-1) contributes to the promise for C2H6-selective separation of C2H6/C2H4. The multi-module pore expansion enables transition from C3H6-selective to more desirable C3H8-selective separation with extraordinarily high C3H8 uptake (254.9 cm3 g-1) and high separation potential (1.25 mmol g-1) for C3H8/C3H6 (50:50 v/v) mixture.

Isoreticular Contraction of Cage-like Metal-Organic Frameworks with Optimized Pore Space for Enhanced C2H2/CO2 and C2H2/C2H4 Separations

The C2H2 separation from CO2 and C2H4 is of great importance yet highly challenging in the petrochemical industry, owing to their similar physical and chemical properties. Herein, the pore nanospace engineering of cage-like mixed-ligand MFOF-1 has been accomplished via contracting the size of the pyridine- and carboxylic acid-functionalized linkers and introducing a fluoride- and sulfate-bridging cobalt cluster, based on a reticular chemistry strategy. Compared with the prototypical MFOF-1, the constructed FJUT-1 with the same topology presents significantly improved C2H2 adsorption capacity, and selective C2H2 separation performance due to the reduced cage cavity size, functionalized pore surface, and appropriate pore volume. The introduction of fluoride- and sulfate-bridging cubane-type tetranuclear cobalt clusters bestows FJUT-1 with exceptional chemical stability under harsh conditions while providing multiple potential C2H2 binding sites, thus rendering the adequate ability for practical C2H2 separation application as confirmed by the dynamic breakthrough experiments under dry and humid conditions. Additionally, the distinct binding mechanism is suggested by theoretical calculations in which the multiple supramolecular interactions involving C-H···O, C-H···F, and other van der Waals forces play a critical role in the selective C2H2 separation.

Bimetallic CPM-37(Ni,Fe) metal-organic framework: enhanced porosity, stability and tunable composition

A newly synthesized series of bimetallic CPM-37(Ni,Fe) metal-organic frameworks with different iron content (Ni/Fe ≈ 2, 1, 0.5, named CPM-37(Ni2Fe), CPM-37(NiFe) and CPM-37(NiFe2)) demonstrated high N2-based specific SBET surface areas of 2039, 1955, and 2378 m2 g-1 for CPM-37(Ni2Fe), CPM-37(NiFe), and CPM-37(NiFe2), having much higher values compared to the monometallic CPM-37(Ni) and CPM-37(Fe) with 87 and 368 m2 g-1 only. It is rationalized that the mixed-metal nature of the materials increases the structural robustness due to the better charge balance at the coordination bonded cluster, which opens interesting application-oriented possibilities for mixed-metal CPM-37 and other less-stable MOFs. In this work, the CPM-37-derived α,β-Ni(OH)2, γ-NiO(OH), and, plausibly, γ-FeO(OH) phases obtained via decomposition in the alkaline medium demonstrated a potent electrocatalytic activity in the oxygen evolution reaction (OER). The ratio Ni : Fe ≈ 2 from CPM-37(Ni2Fe) showed the best OER activity with a small overpotential of 290 mV at 50 mA cm-2, low Tafel slope of 39 mV dec-1, and more stable OER performance compared to RuO2 after 20 h chronopotentiometry at 50 mA cm-2.

Microporous Coordination Polymers for Efficient Recovery of Chloromethane from Organic Silicon Industrial Exhaust Gas

Removal and recovery of methyl chloride (CH3Cl) from exhaust gas of organic silicon industry is highly important from the perspective of environment and economy. For the first time, a tailor-made microporous coordination polymer (Mn-BDC-TPA) was synthesized and applied to the efficient capture and recovery of CH3Cl from related gas mixtures. The high adsorption capacity of CH3Cl (163.4 cm3/g) and high adsorption selectivity of CH3Cl over other impurity gases (1965 for N2, 65 for CH4, and 16 for C2H6) were achieved at 298 K and 100 kPa due to the dual-cage pore system and larger polarizability of CH3Cl. Dynamic breakthrough experiments demonstrate the excellent CH3Cl recovery performance (capacity of >98 cm3/g and purity of >95%) in one adsorption-desorption cycle from the CH3Cl-involved binary, ternary, or quaternary gas mixture.

Finely Tuning Metal Ion Valences of [Fe3-xMx(μ3-OH)(Carboxyl)6(pyridyl)2] Cluster-Based ant-MOFs for Highly Improved CO2 Capture Performances

Solvothermal reactions of different trinuclear precursors and 5-(pyridin-4-yl)isophthalic acid (H2L) successfully led to four anionic ant topological MOFs as Fe3-xMx(μ3-OH)(CH3COO)2(L)2·(DMA+)·DMF [M = Mn(II), Fe(II), Co(II), x = 0, 1, 2 and 3], namely, NJTU-Bai79 [NJTU-Bai = Nanjing Tech University Bai's group, Mn3(μ3-OH)], NJTU-Bai80 [Fe2Mn(μ3-OH)], NJTU-Bai81 [Fe3(μ3-OH)], and NJTU-Bai82 [Fe2Co(μ3-OH)], which possess the narrow pores (2.5-6.0 Å). NJTU-Bai80-82 is able to be tuned to the neutral derivatives [NJTU-Bai80-82(-ox), ox = oxidized] with M2+ ions oxidized to M3+ ones in the air and the OH- ions coordinated on M3+ ions. Very interestingly, selective CO2/N2 adsorptions of NJTU-Bai80-82(-ox) are significantly enhanced with the CO2 adsorption uptakes more than about 6 times that of NJTU-Bai79. GCMC simulations further revealed that neutral NJTU-Bai80-82(-ox) supplies more open frameworks around the -CH3 groups at separate spaces to the CO2 gas molecules with relatively more pores available to them after the removal of counterions. For the first time, finely tuning metal ion valences of metal clusters of ionic MOFs and making them from electrostatic to neutral were adopted for greatly improving their CO2 capture properties, and it would provide another promising strategy for the exploration of high-performance CO2 capture materials.

Pore Space Partition Synthetic Strategy in Imine-linked Multivariate Covalent Organic Frameworks

Partitioning the pores of covalent organic frameworks (COFs) is an attractive strategy for introducing microporosity and achieving new functionality, but it is technically challenging to achieve. Herein, we report a simple strategy for partitioning the micropores/mesopores of multivariate COFs. Our approach relies on the predesign and synthesis of multicomponent COFs through imine condensation reactions with aldehyde groups anchored in the COF pores, followed by inserting additional symmetric building blocks (with C2 or C3 symmetries) as pore partition agents. This approach allowed tetragonal or hexagonal pores to be partitioned into two or three smaller micropores, respectively. The synthesized library of pore-partitioned COFs was then applied for the capture of iodine pollutants (i.e., I2 and CH3I). This rich inventory allowed deep exploration of the relationships between the COF adsorbent composition, pore architecture, and adsorption capacity for I2 and CH3I capture under wide-ranging conditions. Notably, one of our developed pore-partitioned COFs (COF 3-2P) exhibited greatly enhanced dynamic I2 and CH3I adsorption performances compared to its parent COF (COF 3) in breakthrough tests, setting a new benchmark for COF-based adsorbents. Results present an effective design strategy toward functional COFs with tunable pore environments, functions, and properties.

Substituent Engineering in Pore-Space-Partitioned Metal-Organic Frameworks for CO2 Selective Adsorption and Fixation

Comprehensive understanding of substituent groups located on the pore surface of metal-organic frameworks (which we call substituent engineering herein) can help to promote gas adsorption and catalytic performance through ligand functionalization. In this work, pore-space-partitioned metal-organic frameworks (PSP MOFs) were selected as a platform to evaluate the effect of organic functional groups on CO2 adsorption, separation, and catalytic conversion. Twelve partitioned acs metal-organic frameworks (pacs-MOFs, named SNNU-25-Rn here) containing different functional groups were synthesized, which can be classified into electron-donor groups (-OH, -NH2, -CH3, and -OCH3) and electron-acceptor groups (-NO2, -F, -Cl, and -Br). The experimental results showed that SNNU-25-Rn with electron donors usually perform better than those with electron acceptors for the comprehensive utilization of CO2. The CO2 uptake of the 12 SNNU-25-Rn MOFs ranged from 30.9 to 183.6 cm3 g-1 at 273 K and 1 bar, depending on the organic functional groups. In particular, SNNU-25-OH showed the highest CO2 adsorption, SNNU-25-CH3 had the highest IAST of CO2/CH4 (36.1), and SNNU-25-(OH)2 showed the best catalytic activity for the CO2 cycloaddition reaction. The -OH functionalized MOFs with excellent performance may be attributed to the Lewis acid-base and hydrogen-bonding interactions between -OH groups and the CO2 molecules. This work modulated the effect of the microenvironment of MOFs on CO2 adsorption, separation, and catalysis in terms of substituents, providing valuable information for the precise design of porous MOFs with a comprehensive utilization of CO2.

Optimizing Sieving Effect for CO2 Capture from Humid Air Using an Adaptive Ultramicroporous Framework

Excessive CO2 in the air can not only lead to serious climate problems but also cause serious damage to humans in confined spaces. Here, a novel metal-organic framework (FJI-H38) with adaptive ultramicropores and multiple active sites is prepared. It can sieve CO2 from air with the very high adsorption capacity/selectivity but the lowest adsorption enthalpy among the reported physical adsorbents. Such excellent adsorption performances can be retained even at high humidity. Mechanistic studies show that the polar ultramicropore is very suitable for molecular sieving of CO2 from N2 , and the distinguishable adsorption sites for H2 O and CO2 enable them to be co-adsorbed. Notably, the adsorbed-CO2 -driven pore shrinkage can further promote CO2 capture while the adsorbed-H2 O-induced phase transitions in turn inhibit H2 O adsorption. Moreover, FJI-H38 has excellent stability and recyclability and can be synthesized on a large scale, making it a practical trace CO2 adsorbent. This will provide a new strategy for developing practical adsorbents for CO2 capture from the air.

Multi-Modular Design of Stable Pore-Space-Partitioned Metal-Organic Frameworks for Gas Separation Applications

Pore space partition (PSP) is an effective materials design method for developing high-performance small-pore materials for storage and separation of gas molecules. The continued success of PSP depends on broad availability and judicious choice of pore-partition ligands and better understanding of each structural module on stability and sorption properties. Here, by using substructural bioisosteric strategy (sub-BIS), a dramatic expansion of pore-partitioned materials is targeted by using ditopic dipyridyl ligands with non-aromatic cores or extenders, as well as by expanding heterometallic clusters to uncommon nickel-vanadium and nickel-indium clusters rarely known before in porous materials. The dual-module iterative refinement of pore-partition ligands and trimers leads to remarkable enhancement of chemical stability and porosity. Here a family of 23 pore-partitioned materials synthesized from five pore-partition ligands and seven types of trimeric clusters is reported. New materials with such compositionally and structurally diverse framework modules reveal key factors that dictate stability, porosity, and gas separation properties. Among these, materials based on heterometallic vanadium-nickel trimeric clusters give rise to the highest long-term hydrolytic stability and remarkable uptake capacity for CO2 , C2 H2 /C2 H4 /C2 H6 , and C3 H6 /C3 H8 hydrocarbon gases. The breakthrough experiment shows the potential application of new materials for separating gas mixtures such as C2 H2 /CO2 .

Stepwise construction of multi-component metal-organic frameworks

Multi-component metal-organic frameworks (MC-MOFs) are crystalline porous materials containing multiple organic ligands or mixed metals, which manifest new properties beyond the linear combination of the single component. However, the traditional one-pot synthesis method for MOFs is not always applicable for synthesizing MC-MOFs due to the competitive coordination of multiple ligands and metals. Therefore, the stepwise construction of MC-MOFs has been explored, which enables more precise control of the heterogeneity within the ordered MC-MOFs. This review provides a summary of the synthesis strategies, namely, ligand exchange, coordinative modification, covalent modification, ligand metalation, cluster metalation, and use of mixed-metal precursors, for the stepwise construction of MC-MOFs. Furthermore, we discuss the applications of MC-MOFs with ordered arrangements of multiple functionalities, focusing on gas adsorption and separation, water remediation, heterogeneous catalysis, luminescence, and chemical sensing.

Metal-organic framework-based nanomaterials for CO2 storage: A review

The increasing recognition of the impact of CO2 emissions as a global concern, directly linked to the rise in global temperature, has raised significant attention. Carbon capture and storage, particularly in association with adsorbents, has occurred as a pivotal approach to address this pressing issue. Large surface area, high porosity, and abundant adsorption sites make metal-organic frameworks (MOFs) promising contenders for CO2 uptake. This review commences by discussing recent advancements in MOFs with diverse adsorption sites, encompassing open metal sites and Lewis basic centers. Next, diverse strategies aimed at enhancing CO2 adsorption capabilities are presented, including pore size manipulation, post-synthetic modifications, and composite formation. Finally, the extant challenges and anticipated prospects pertaining to the development of MOF-based nanomaterials for CO2 storage are described.

Pore Space Partitioning MIL-88(Co): Developing Robust Adsorbents for CO2/CH4 Separation Featured with High CO2 Adsorption and Rapid Desorption

Metal-organic frameworks (MOFs) have attracted significant attention as sorbents for gas separation and purification. Ideally, an industrially potential adsorbent should combine exceptional gas uptake, excellent stability, and a lower regeneration energy; however, it remains a great challenge. Here, by utilizing the pore space partition (PSP) strategy, we develop three isostructural MOF materials (Co-BDC-TPB, Co-DCBDC-TPB, and Co-DOBDC-TPB) based on pristine MIL-88(Co). The three pore-space-partitioned crystalline microporous MOFs have triangular bipyramid cages and segmented one-dimensional channels, and among them, Co-DOBDC-TPB exhibits the highest CO2 uptake capacity (4.35 mmol g-1) and good CO2/N2 (29.7) and CO2/CH4 (6.2) selectivity. The selectivity-capacity synergy endows it with excellent CO2/N2 and CO2/CH4 separation performance. Moreover, Co-DOBDC-TPB can complete desorption within 10 min. The satisfactory CO2 adsorption ability can be attributed to both microporous aperture arising from PSP and modification of the pore surface by the polar hydroxy group, which enhances the interaction between Co-DOBDC-TPB and CO2 molecules significantly. The exceptional regeneration property may be due to its lower CO2 isosteric heat of adsorption (23.6 kJ/mol). The developed pore-space-partitioned MIL-88(Co) material Co-DOBDC-TPB may have potential application to flue gas and natural gas purification.

Cyclobutanedicarboxylate Metal-Organic Frameworks as a Platform for Dramatic Amplification of Pore Partition Effect

Ultrafine tuning of MOF structures at subangstrom or picometer levels can help improve separation selectivity for gases with subtle differences. However, for MOFs with a large enough pore size, the effect from ultrafine tuning on sorption can be muted. Here we show an integrative strategy that couples extreme pore compression with ultrafine pore tuning. This strategy is made possible by unique combination of two features of the partitioned acs (pacs) platform: multimodular framework and exceptional tolerance toward isoreticular replacement. Specifically, we use one module (ligand 1, L1) to shrink the pore size to an extreme minimum on pacs. A compression ratio of about 30% was achieved (based on the unit cell c/a ratio) from prototypical 1,4-benzenedicarboxylate-pacs to trans-1,3-cyclobutanedicarboxylate-pacs. This is followed by using another module (ligand 2, L2) for ultrafine pore tuning (<3% compression). This L1-L2 strategy increases the C2H2/CO2 selectivity from 2.6 to 20.8 and gives rise to an excellent experimental breakthrough performance. As the shortest cyclic dicarboxylate that mimics p-benzene-based moieties using a bioisosteric (BIS) strategy on pacs, trans-1,3-cyclobutanedicarboxylate offers new opportunities in MOF chemistry.

Simultaneous Control of Flexibility and Rigidity in Pore-Space-Partitioned Metal-Organic Frameworks

Flexi-MOFs are typically limited to low-connected (<9) frameworks. Here we report a platform-wide approach capable of creating a family of high-connected materials (collectively called CPM-220) that integrate exceptional framework flexibility with high rigidity. We show that the multi-module nature of the pore-space-partitioned pacs (partitioned acs net) platform allows us to introduce flexibility as well as to simultaneously impose high rigidity in a tunable module-specific fashion. The inter-modular synergy has remarkable macro-morphological and sub-nanometer structural impacts. A prominent manifestation at both length scales is the retention of X-ray-quality single crystallinity despite huge hexagonal c-axial contraction (≈ 30%) and harsh sample treatment such as degassing and sorption cycles. CPM-220 sets multiple precedents and benchmarks on the pacs platform in both structural and sorption properties. They possess exceptionally high benzene/cyclohexane selectivity, unusual C₃H₆ and C₃H₈ isotherms, and promising separation performance for small gas molecules such as C₂H₂/CO₂.

Solvent-free Synthesis of Multi-Module Pore-Space-Partitioned Metal-Organic Frameworks for Gas Separation

Multi-module design of framework materials with multiple distinct building blocks has attracted much attention because such materials are more amenable to compositional and geometrical tuning and thus offer more opportunities for property optimization. Few examples are known that use environmentally friendly and cost-effective solvent-free method to synthesize such materials. Here, we report the use of solvent-free method (also modulator-free) to synthesize a series of multi-module MOFs with high stability and separation property for C₂ H₂ /CO₂ . The synthesis only requires simple mixing of reactants and short reaction time (2 h). Highly porous and stable materials can be made without any post-synthetic activation. The success of solvent-free synthesis of multi-module MOFs reflects the synergy between different modules, resulting in stable pore-partitioned materials, despite the fact that other competitive crystallization pathways with simpler framework compositions also exist.

Highly Stable Fe/Co-TPY-MIL-88(NH2) Metal-Organic Framework (MOF) in Enzymatic Cascade Reactions for Chemiluminescence-Based Detection of Extracellular Vesicles

Metal-Organic Frameworks (MOFs) can deliver many advantages when acting as enzyme mimics to assist with signal amplification in molecular detection: they have abundant active catalytic sites per unit volume of the material; their structures and elemental compositions are highly tunable, and their high specific surface area and porous property can assist with target separation and enrichment. In the present work, we have demonstrated that, by adding the pore partition agent, 2,4,6-tris(4-pyridyl)pyridine (TPY) during synthesis of the bimetallic Fe/Co-MIL-88(NH₂) MOF to block the open metal sites, a highly porous MOF of Fe/Co-TPY-MIL-88(NH₂) can be produced. This material also exhibits high stability in basic solutions and biofluids and possesses high peroxidase-mimicking activity, which can be utilized to produce long-lasting chemiluminescence (CL) from luminol and H₂O₂. Moreover, acting as the peroxidase-mimic, the Fe/Co-TPY-MIL-88(NH₂) MOF can form the enzymatic cascade with glucose oxidase (GOx) for biomarker detection. When applied to detect extracellular vesicles (EVs), the MOF material and GOx are brought to the proximity on the EVs through two surface proteins, which triggers the enzyme cascade to produce high CL from glucose and luminol. EVs within the concentration range of 5 × 10⁵ to 4 × 10⁷ particles/mL can be detected with an LOD of 1 × 10⁵ particles/mL, and the method can be used to analyze EV contents in human serum without sample preparation and EV purification. Overall, our work demonstrates that the high versatility and tunability of the MOF structures could bring in significant benefits to biosensing and enable ultrasensitive detection of biomarkers with judicious material designs.

Concurrent Enhancement of Acetylene Uptake Capacity and Selectivity by Progressive Core Expansion and Extra-Framework Anions in Pore-Space-Partitioned Metal-Organic Frameworks

A multi-stage core-expansion method is proposed here as one component of the integrative binding-site/extender/core-expansion (BEC) strategy. The conceptual deconstruction of the partitioning ligand into three editable parts draws our focus onto progressive core expansion and allows the optimization of both acetylene uptake and selectivity. The effectiveness of this strategy is shown through a family of eight cationic pore-partitioned materials containing three different partitioning ligands and various counter anions. The optimized structure, Co₃ -cpt-tph-Cl (Hcpt=4-(p-carboxyphenyl)-1,2,4-triazole, H-tph=(2,5,8-tri-(4-pyridyl)-1,3,4,6,7,9-hexaazaphenalene) with the largest surface area and highest C₂ H₂ uptake capacity (200 cm³ /g at 298 K), also exhibits (desirably) the lowest CO₂ uptake and hence the highest C₂ H₂ /CO₂ selectivity. The successful boost in both C₂ H₂ capacity and IAST selectivity allows Co₃ -cpt-tph-Cl to rank among the best crystalline porous materials, ionic MOFs in particular, for C₂ H₂ uptake and C₂ H₂ /CO₂ experimental breakthrough separation.

Developing Water-Stable Pore-Partitioned Metal-Organic Frameworks with Multi-Level Symmetry for High-Performance Sorption Applications

A new perspective is proposed in the design of pore-space-partitioned MOFs that is focused on ligand symmetry properties sub-divided here into three hierarchical levels: 1) overall ligand, 2) ligand substructure such as backbone or core, and 3) the substituent groups. Different combinations of the above symmetry properties exist. Given the close correlation between nature of chemical moiety and its symmetry, such a unique perspective into ligand symmetry and sub-symmetry in MOF design translates into the influences on MOF properties. Five new MOFs have been prepared that exhibit excellent hydrothermal stability and high-performance adsorption properties with potential applications such as C₃ H₆ /C₂ H₄ and C₂ H₂ /CO₂ selective adsorption. The combination of high stability with high benzene/cyclohexane selectivity of ≈13.7 is also of particular interest.

Ligand-Functional Groups Induced Tuning MOFs' 2D into 1D Pore Channels for Pipeline Natural Gas Purification

The solvothermal reactions of CoCl₂  ⋅ 6H₂ O, 3,5-pyridinedicarboxylic acid (H₂ L) and isonicotinic acid (HL₁ )/3-amino isonicotinic acid (HL₂ )/3-chloro isonicotinic acid (HL₃ ) successfully led to three tfz-d topological pillar-layer [Co₄ (μ-F)₂ (COO)₆ (NC₅ H₄ )₄ ] cluster-based MOFs, namely, [Co₄ (μ-F)₂ (L)₂ (L₁ )₂  ⋅ 2DMA] ⋅ DMA ⋅ 2H₂ O (SNNU-Bai76, SNNU-Bai=Shaanxi Normal University Bai's group), [Co₄ (μ-F)₂ (L)₂ (L₂ )₂  ⋅ 2H₂ O] ⋅ 2DMA ⋅ 2H₂ O (SNNU-Bai77) and [Co₄ (μ-F)₂ (L)₂ (L₃ )₂  ⋅ 2H₂ O] ⋅ 2DMF ⋅ 2H₂ O (SNNU-Bai78). With the 2D pore channels in SNNU-Bai76 and SNNU-Bai77 being tuned to the 1D pore channel in SNNU-Bai78, C₃ H₈ and C₂ H₆ adsorption uptakes are apparently improved and the IAST selectivities of C₃ H₈ /CH₄ and C₂ H₆ /CH₄ almost remain, which indicate that SNNU-Bai78 may be one potential separation material for the pipeline natural gas purification. These were further confirmed by the breakthrough experiments for the simulated pipeline natural gas (C₃ H₈ /C₂ H₆ /CH₄  : 5/10/85 gas mixture) of three isostructural MOFs. Furthermore, GCMC simulations revealed that due to one of the pore channels blocked by Cl atoms in a couple of 3-chloro isonicotinic acid with the changed conformation as the pillar, the pore wall of the formed 1D pore channel in SNNU-Bai78 may interact with the adsorbed C₃ H₈ or C₂ H₆ molecule more strongly, for which more atoms of framework at the new adsorption site will interact with the adsorbed gas molecule by more intermolecular interactions. This was also evidenced by the increased binding energies, being consistent with the tuning of adsorption enthalpies for C₃ H₈ and C₂ H₆ gas molecules, and the reduced C₃ H₈ and C₂ H₆ gas diffusion coefficients in SNNU-Bai78. Very interestingly, this work is the first example of finely tuning the pore connectivity of MOFs toward strengthened host-guest interactions for the gas adsorption and separation.

Optimization of Pore-Space-Partitioned Metal–Organic Frameworks Using the Bioisosteric Concept

Pore space partitioning (PSP) is methodically suited for dramatically increasing the density of guest binding sites, leading to the partitioned acs (pacs) platform capable of record-high uptake for CO₂ and small hydrocarbons such as C₂H_x. For gas separation, achieving high selectivity amid PSP-enabled high uptake offers an enticing prospect. Here we aim for high selectivity by introducing the bioisosteric (BIS) concept, a widely used drug design strategy, into the realm of pore-space-partitioned MOFs. New pacs materials have high C₂H₂/CO₂ selectivity of up to 29, high C₂H₂ uptake of up to 144 cm³/g (298 K, 1 atm), and high separation potential of up to 5.3 mmol/g, leading to excellent experimental breakthrough performance. These metrics, coupled with exceptional tunability, high stability, and low regeneration energy, demonstrate the broad potential of the BIS-PSP strategy.

Precise Introduction of Single Vanadium Site into Indium-Organic Framework for CO2 Capture and Photocatalytic Fixation

The capture and fixation of CO₂ under mild conditions is a cost-effective route to reduce greenhouse gases, but it is challenging because of the low conversion and selectivity issues. Metal-organic frameworks (MOFs) are promising in the fields of adsorption and catalysis because of their structural tunability and variability. However, the precise structural design of MOFs is always pursued and elusive. In this work, a metal-mixed MOF (SNNU-97-InV) was designed by precisely introducing single vanadium site into the isostructural In-MOF (SNNU-97-In). The single V sites clearly change the interactions between the MOF framework and CO₂ molecules, leading to a 71.3% improvement in the CO₂ adsorption capacity. At the same time, the enhanced light absorption enables SNNU-97-InV to efficiently convert CO₂ into cyclic carbonates (CCs) with epoxides under illumination. Controlled experiments showed that the promoted performance of SNNU-97-InV may be that the V═O site can more easily combine with CO₂ and convert them into an intermediate state under illumination, and the possible mechanism was thus speculated.

Two cationic iron-based crystalline porous materials for encapsulation and sustained release of 5-fluorouracil

Iron-based crystalline porous materials (CPMs) emerged as a new class of biodegradable and non-toxic materials of high interest for drug delivery systems (DDSs) due to their high loading capacity and controllable structures. This work constructed two kinds of Fe-CPM coordination polymers (CPM-83 and CPM-85) from typical oxo-centered trimers of the iron octahedra cluster [Fe₃O(RCOO)₃(TPT)] with two functional modules. The tri-topic pyridine ligand (TPT) occupied the open metal sites of the trinuclear cluster, precluding the attachment of neutralizing anions, leading to three-dimensional frameworks with a positive charge and higher stability. Moreover, the triazine ligand TPT divides the original columnar channel into small domains, improving the adsorption efficiency and maximizing the host-guest interaction. Hence, the suitable pore size and electrostatic force make the materials highly adsorption selective for the anticancer drug 5-fluorouracil (5-Fu). We show that Fe-CPM-83 and Fe-CPM-85 loaded with 5-Fu are efficient drug delivery vehicles with loading content as high as 60.5 (wt%) and 32.8 (wt%) within 2-5 h of loading time. Simultaneously, their sustained release kinetics can be up to 96 hours with a completely different pH-responsive controlled release. The released content is 77% or 85% for each complex, significantly prolonging the release process and decreasing the plasma concentration. The MTT assay was performed on mouse fibroblasts (L929) to demonstrate the satisfactory biocompatibility of the matrix. This work has momentous research significance and application value for developing novel drug-delivery materials.

Dinuclear Nickel-Oxygen Cluster-Based Metal-Organic Frameworks with Octahedral Cages for Efficient Xe/Kr Separation

Xe/Kr separation is industrially important but remains a daunting issue in chemical separations. Herein, a fluorinated metal-organic framework (MOF), [Ni₂(μ₂-O)(TFBPDC)(tpt)₂]_n (named JXNU-13-F), built from 3,3',5,5'-tetrakis(fluoro)biphenyl-4,4'-dicarboxylic (TFBPDC^2-) and 2,4,6-tri(4-pyridinyl)-1,3,5-triazine (tpt) ligands is provided. JXNU-13-F displays a three-dimensional (3D) framework constructed from distorted octahedral cages and an impressive Xe capacity of 144 cm³ g^-1 at 273 K and 1 bar, ranking among top MOFs. The high Xe uptake and moderate Xe/Kr adsorption selectivity endow JXNU-13-F with efficient Xe/Kr separation demonstrated by experimental column breakthrough tests. The comparative studies of gas adsorption between isostructural JXNU-13-F and JXNU-13 (the nonfluorinated analogue ([Ni₂(μ₂-O)(BPDC))(tpt)₂]_n with biphenyl-4,4'-dicarboxylic (BPDC^2-)) revealed that the F groups serve as the innocent groups during the Xe and Kr adsorption in JXNU-13-F. Thus, a combination of highly hydrophobic and π-electron-rich pore surfaces made of aromatic rings with strong interactions with the Xe atom possessing large polarizability and appropriate pore sizes that match well Xe having a large atom diameter has resulted in high Xe uptake and effective Xe/Kr separation characteristics of JXNU-13-F.

Modulation of Hierarchical Pores in Metal-Organic Frameworks for Improved Dye Adsorption and Electrocatalytic Performance

The hierarchical porous metal-organic framework (HP-MOF) has emerged as a hot topic in porous materials in consideration of their advantages in storage capacity and catalysis performance. Herein, we report the construction and property investigation of a series of HP-MOFs. A series of isoreticular microporous MOFs featuring the pacs topology network based on 2,4,6-tris(4-pyridyl)-1,3,5-triazine and different carboxylic acid ligands are found to be potential precursors to construct HP-MOFs. Through the decarboxylation of carboxylate ligands at high temperatures, a hierarchical porous structure could be obtained with the reservation of a crystalline framework. The formation of hierarchical pores is highly dependent on the structural and component nature (carboxylate ligands and metal centers) of the pristine MOF and the pyrolysis conditions (temperature and treatment time), indicating the highly tunable hierarchical pore characteristic of the HP-MOFs. By taking advantage of the increased pore volume and more exposed activation sites, the HP-MOFs reveal enhanced anionic dye adsorption capacity (800 mg·g^-1 for Congo red and 140 mg·g^-1 for methyl blue) and catalytic activity toward electrocatalytic oxygen reduction reaction (overpotential of 0.302 V at a current density of 10 mA·cm^-2, 51 mV lower than that of the pristine MOF).

A (3,8)-Connected Metal-Organic Framework with Bending Dicarboxylate Linkers for C2H2/CO2 Separation

Herein, by replacement of the linear terephthalate linker with the bending 2,5-thiophenedicarboxylate (tdc^2-) linker in the typical (3,9)-connected metal-organic framework, with a reduced 8-connected hydroxyl-centered trinuclear cluster, a new (3,8)-connected network, [Ni₃(μ₃-OH)(tdc)₃(tpp)] [DZU-1; tpp = 2,4,6-tris(4-pyridyl)pyridine], was synthesized. The modified pore environment enables DZU-1 to selectively adsorb C₂H₂ over CO₂ in an efficient manner.

Synthesis, Structure and Highly Selective C3H8/CH4 and C2H6/CH4 Adsorptions of a (4,8)-c Ternary flu-Metal-organic Framework based upon both [Sc4O2(COO)8] and [Cu4OCl6] Clusters

A new ternary flu topological metal-organic framework based upon the torsional cubic 8-connected [Sc4O2(COO)8] cluster and the tetrahedral 4-connected [Cu4OCl6] cluster, namely, [Sc4O2(Cu4Cl6O)2(L)8•5H2O]•xGuest (SNNU-Bai69; SNNU-Bai = Shaanxi Normal University, Bai’s...

Pore-Space Partition through an Embedding Metal-Carboxylate Chain-Induced Topology Upgrade Strategy for the Separation of Acetylene/Ethylene

Ethylene (C₂H₄) is one of the most significant substances in the petrochemical industry; however, the capture of acetylene (C₂H₂) in about 1% from C₂H₂/C₂H₄ mixtures is a difficult task because of the similarity of their physical properties. With the aggravation of the energy crisis, using metal-organic framework (MOF) materials to purify C₂H₄ through adsorptive separation is a promising way to save energy and reduce emission. Pore-space partition (PSP) with the aim of enhancing the density of the binding sites and the strength of the host-guest interactions is an effective means to promote a solution for the challenging gas separation problems. Herein, we report a new embedding metal-carboxylate chain-induced topology upgrade strategy within a MOF to realize PSP and separation of C₂H₂/C₂H₄ mixtures. As a proof of concept, we construct a microporous MOF (NUM-12) utilizing the in situ insertion of cobalt terephthalic chains into a pretargeted ant-type framework during synthesis. Because of the attainment of an elaborately tuned aperture size and a specific pore environment through this strategy, NUM-12a (activated NUM-12) not only has a remarkable gas sorption capacity and strong interactions for C₂H₂ but also possesses an excellent purification performance for C₂H₂/C₂H₄ mixtures. Both experiments and simulation calculations clearly reveal that NUM-12 is a promising candidate for the separation of C₂H₂/C₂H₄, proving the feasibility of this new strategy for developing newly fashioned MOFs with adjustable structure and performance.

Symmetry-Guided Synthesis of N,N'-Bicarbazole and Porphyrin-Based Mixed-Ligand Metal-Organic Frameworks: Light Harvesting and Energy Transfer

In the past decades, many attempts have been made to mimic the energy transfer (EnT) in photosynthesis, a key process occurring in nature that is of fundamental significance in solar fuels and sustainable energy. Metal-organic frameworks (MOFs), an emerging class of porous crystalline materials self-assembled from organic linkers and metal or metal cluster nodes, offer an ideal platform for the exploration of directional EnT phenomena. However, placing energy donor and acceptor moieties within the same framework with an atomistic precision appears to be a major synthesis challenge. In this work, we report the design and synthesis of a highly porous and photoactive N,N'-bicarbazole- and porphyrin-based mixed-ligand MOF, namely, NPF-500-H₂TCPP (NPF = Nebraska porous framework; H₂TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin), where the secondary ligand H₂TCPP is incorporated precisely through the open metal sites of the equatorial plane of the octahedron cage resulting from the underlying (4,8) connected network of NPF-500. The efficient EnT process from N,N'-bicarbazole to porphyrin in NPF-500-H₂TCPP was captured by time-resolved spectroscopy and exemplified by photocatalytic oxidation of thioanisole. These results demonstrate not only the capability of NPF-500 as the scaffold to precisely arrange the donor-acceptor assembly for the EnT process but also the potential to directly utilize the EnT process for photocatalytic applications.

Pore-Space Partition and Optimization for Propane-Selective High-Performance Propane/Propylene Separation

The development of effective propane (C3H8)-selective adsorbents for the purification of propylene (C3H6) from C3H8/C3H6 mixture is a promising alternative to replace the energy-intensive cryogenic distillation. However, few materials possess the dual desirable features of propane selectivity and high uptake capacity. Here, we report a family of pore-space-partitioned crystalline porous materials (CPM) with remarkable C3H8 uptake capacity (up to 10.9 mmol/g) and the highly desirable yet uncommon C3H8 selectivity (up to 1.54 at 0.1 bar and 1.44 at 1 bar). The selectivity-capacity synergy endows them with record-performing C3H8/C3H6 separation potential (i.e., C3H6 recovered from the mixture). Moreover, these CPMs exhibit outstanding properties including high stability, low regeneration energy, and multimodular chemical and geometrical tunability within the same isoreticular framework. The high C3H8/C3H6 separation performance was further confirmed by the breakthrough experiments.

Ultrastable High-Connected Chromium Metal-Organic Frameworks

State-of-the-art MOFs are generally known for chemical stability at one end of the pH scale (i.e., pH < 0 or pH > 14). Herein, we report new Cr-MOFs capable of withstanding extreme pH conditions across approximately 16 pH units from pH < 0 to pH > 14, likely the largest observed pH range for MOFs. The integration of multiple stability-enhancing factors including nonlabile Cr³⁺, mixed Cr-N and Cr-O cross-links, and the highest possible connectivity by Cr₃O trimers enables extraordinary chemical stability confirmed by both PXRD and gas adsorption. Notably, the base stability is much higher than literature Cr-MOFs, thereby revitalizing Cr-MOF's viability in the pursuit for the most chemically stable MOFs. Among known cationic MOFs, the chemical stability of these new Cr-MOFs is unmatchable, to our knowledge. These Cr-MOFs can be developed into multiseries of isoreticular MOFs with a rich potential for functionalization, pore size, and pore geometry engineering and applications.

A Highly Selective Supramolecule Array Membrane Made of Zero-Dimensional Molecules for Gas Separation

We orderly assembled zero-dimensional 2-methylimidazole (mim) molecules into unprecedented supramolecule array membranes (SAMs) through solvent-free vapor processing, realizing the intermolecular spacing of mim at ca. 0.30 nm available as size-sieving channels for distinguishing the tiny difference between H2 (kinetic diameter: 0.289 nm) and CO2 (kinetic diameter: 0.33 nm). The highly oriented and dense membranes yield a separation factor above 3600 for equimolar H2 /CO2 mixtures, which is one order of magnitude higher than those of the state-of-the-art membranes defining 2017's upper bound for H2 /CO2 separation. These SAMs define a new benchmark for molecular sieve membranes and are of paramount importance to precombustion carbon capture. Given the range of supramolecules, we anticipate SAMs with variable intermolecular channels could be applied in diversified separations that are prevalent in chemical processes.