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.

Cooperative Immobilization of Transition-Metal Clusters into Kagome-Type Metal-Organic Framework for CH/CO Separation.

There has long been a pursuit for a metal-organic framework (MOF)-based adsorbent for various hydrocarbon separations. Herein, we utilized simple trimesic acid and 1,2,4-triazole, together with the heterometallic strategy to produce two quaternary MOFs with a kgm-type structure. The cooperative coordination allows the immobilization of metal clusters into the pore channels, creating an appropriate pore size and high density of open metal sites.

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.

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.

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

Trigonal planar M(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 M(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 MM pacs made from co-assembly between M single-deck trimer and M double-deck trimer.

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.

Multilevel-Regulated Metal-Organic Framework Platform Integrating Pore Space Partition and Open-Metal Sites for Enhanced CO Photoreduction to CO with Nearly 100% Selectivity.

Rational design and regulation of atomically precise photocatalysts are essential for constructing efficient photocatalytic systems tunable at both the atomic and molecular levels. Herein, we propose a platform-based strategy capable of integrating both pore space partition (PSP) and open-metal sites (OMSs) as foundational features for constructing high-performance photocatalysts. We demonstrate the first structural prototype obtained from this strategy: pore-partitioned NiTCPE- (TCPE = 1,1,2,2-tetra(4-carboxylphenyl)ethylene, = partitioned topology).

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.

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.

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 (partitioned net) platform allows us to introduce flexibility as well as to simultaneously impose high rigidity in a tunable module-specific fashion.

De-Linker-Enabled Exceptional Volumetric Acetylene Storage Capacity and Benchmark C H /C H and C H /CO Separations in Metal-Organic Frameworks.

An ideal adsorbent for separation requires optimizing both storage capacity and selectivity, but maximizing both or achieving a desired balance remain challenging. Herein, a de-linker strategy is proposed to address this issue for metal-organic frameworks (MOFs). Broadly speaking, the de-linker idea targets a class of materials that may be viewed as being intermediate between zeolites and MOFs.

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.

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 CO and small hydrocarbons such as CH. 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.

In Situ Synthesized Homochiral Spiroborate Ester Metal-Organic Framework with Mono-, Di-, and Trivalent Cations.

We report here a one-step method for synthesizing multi-component and in-situ-formed homochiral spiroborate-ester-based metal-organic framework CPM-B1. This unique material successfully integrates COF fragment spiroborate ester within the MOF and simultaneously incorporate homochirality and helicity. In addition, CPM-B1 is a rare example of framework materials that results from the cooperative assembly of three charge-complementary cations: +1 (lithium), +2 (cobalt), and +3 (boron).

Metal-Mediated Directional Capping of Rod-Packing Metal-Organic Frameworks.

Two new rod-packing metal-organic frameworks (RPMOF) are constructed by regulating the in situ formation of the capping agent. In CPM-s7, carboxylate linkers extend 1D manganese-oxide chains in four additional directions, forming 3D RPMOF. The substitution of Mn with a stronger Lewis acidic Co , leads to an acceleration of the hydrolysis-prone sulfonate linker, resulting in presence of sulfate ions to reduce two out of the four carboxylate-extending directions, and thus forming a new 2D rod-packing CPM-s8.

Simultaneous Control of Pore-Space Partition and Charge Distribution in Multi-Modular Metal-Organic Frameworks.

We report here a strategy for making anionic pacs type porous materials by combining pore space partition with charge reallocation. The method uses the first negatively charged pore partition ligand (2,5,8-tri-(4-pyridyl)-1,3,4,6,7,9-hexaazaphenalene, H-tph) that simultaneously enables pore partition and charge reallocation. Over two dozen anionic pacs materials have been made to demonstrate their excellent chemical stability and a high degree of tunability.

Atomically precise metal chalcogenide supertetrahedral clusters: frameworks to molecules, and structure to function.

Metal chalcogenide supertetrahedral clusters (MCSCs) are of significance for developing crystalline porous framework materials and atomically precise cluster chemistry. Early research interest focused on the synthetic and structural chemistry of MCSC-based porous semiconductor materials with different cluster sizes/compositions and their applications in adsorption-based separation and optoelectronics. More recently, focus has shifted to the cluster chemistry of MCSCs to establish atomically precise structure-composition-property relationships, which are critical for regulating the properties and expanding the applications of MCSCs.

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).

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

The development of effective propane (CH)-selective adsorbents for the purification of propylene (CH) from CH/CH 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 CH uptake capacity (up to 10.

Ultrahigh-Uptake Capacity-Enabled Gas Separation and Fruit Preservation by a New Single-Walled Nickel-Organic Framework.

High gas-uptake capacity is desirable for many reasons such as gas storage and sequestration. Moreover, ultrahigh capacity can enable a practical separation process by mitigating the selectivity factor that sometimes compromises separation efficiency. Herein, a single-walled nickel-organic framework with an exceptionally high gas capture capability is reported.

Selective Crystallization of Rare-Earth Ions into Cationic Metal-Organic Frameworks for Rare-Earth Separation.

For rare-earth separation, selective crystallization into metal-organic frameworks (MOFs) offers new opportunities. Especially important is the development of MOF platforms with high selectivity toward target ions. Here we report a MOF platform (CPM-66) with low-coordination-number environment for rare-earth ions.

Metal Chalcogenide Supertetrahedral Clusters: Synthetic Control over Assembly, Dispersibility, and Their Functional Applications.

ConspectusMetal chalcogenide supertetrahedral clusters (MCSCs) bear the closest structural resemblance to II-VI or I-III-VI semiconductor nanocrystals and can be considered as well-defined ultrasmall "quantum dots" (QDs). Compared to traditional colloidal QDs that are typically associated with size dispersity, irregular surface atomic structures, poorly defined core-ligand interfaces, and random defect/dopant sites, the nano- or subnano-sized MCSCs feature precise structural properties such as atomically uniform size, precise structure, and ordered dopant distribution, all of which offer ample opportunities for a broad and in-depth understanding of the correlation between the precise local structure and site- or size-dependent properties, which are critical to the exploitation of their functional applications. Our previous Account in 2005 provided a narrative on the efforts to expand the structural diversity of open-framework materials using different-sized and compositionally tunable clusters as building blocks with a primary objective of integrating the semiconducting properties with porosity in zeolite-type solids.