Quan-Guo Zhai

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

Metal-organic frameworks (MOFs) with the highest CO(2) uptake capacity are usually those equipped with open metal sites. Here we seek alternative strategies and mechanisms for developing high-performance CO(2) adsorbents. We demonstrate that through a ligand insertion pore space partition strategy, we can create crystalline porous materials (CPMs) with superior CO(2) uptake capacity. Specifically, a new material, CPM-33b-Ni without any open metal sites, exhibits the CO(2) uptake capacity comparable to MOF-74 with the same metal (Ni) at 298 K and 1 bar.

Systematic and Dramatic Tuning on Gas Sorption Performance in Heterometallic Metal-Organic Frameworks

Despite their having much greater potential for compositional and structural diversity, heterometallic metal-organic frameworks (MOFs) reported so far have lagged far behind their homometallic counterparts in terms of CO2 uptake performance. Now the power of heterometallic MOFs is in full display, as shown by a series of new materials (denoted CPM-200s) with superior CO2 uptake capacity (up to 207.6 cm(3)/g at 273 K and 1 bar), close to the all-time record set by MOF-74-Mg. The isosteric heat of adsorption can also be tuned from -16.4 kJ/mol for CPM-200-Sc/Mg to -79.6 kJ/mol for CPM-200-V/Mg. The latter value is the highest reported for MOFs with Lewis acid sites. Some members of the CPM-200s family consist of combinations of metal ions (e.g., Mg/Ga, Mg/Fe, Mg/V, Mg/Sc) that have never been shown to coexist in any known crystalline porous materials. Such previously unseen combinations become reality through a cooperative crystallization process, which leads to the most intimate form of integration between even highly dissimilar metals, such as Mg(2+) and V(3+). The synergistic effects of heterometals bestow CPM-200s with the highest CO2 uptake capacity among known heterometallic MOFs and place them in striking distance of the all-time CO2 uptake record.

Cooperative Crystallization of Heterometallic Indium-Chromium Metal-Organic Polyhedra and Their Fast Proton Conductivity.

Metal-organic polyhedra (MOPs) or frameworks (MOFs) based on Cr(3+) are notoriously difficult to synthesize, especially as crystals large enough to be suitable for characterization of the structure or properties. It is now shown that the co-existence of In(3+) and Cr(3+) induces a rapid crystal growth of large single crystals of heterometallic In-Cr-MOPs with the [M8L12] (M=In/Cr, L=dinegative 4,5-imidazole-dicarboxylate) cubane-like structure. With a high concentration of protons from 12 carboxyl groups decorating every edge of the cube and an extensive H-bonded network between cubes and surrounding H2O molecules, the newly synthesized In-Cr-MOPs exhibit an exceptionally high proton conductivity (up to 5.8×10(-2) S cm(-1) at 22.5 °C and 98% relative humidity, single crystal).

An ultra-tunable platform for molecular engineering of high-performance crystalline porous materials

Metal-organic frameworks are a class of crystalline porous materials with potential applications in catalysis, gas separation and storage, and so on. Of great importance is the development of innovative synthetic strategies to optimize porosity, composition and functionality to target specific applications. Here we show a platform for the development of metal-organic materials and control of their gas sorption properties. This platform can accommodate a large variety of organic ligands and homo- or hetero-metallic clusters, which allows for extraordinary tunability in gas sorption properties. Even without any strong binding sites, most members of this platform exhibit high gas uptake capacity. The high capacity is accomplished with an isosteric heat of adsorption as low as 20 kJ mol−1 for carbon dioxide, which could bring a distinct economic advantage because of the significantly reduced energy consumption for activation and regeneration of adsorbents.

Synthesis, Crystal Structures, and Photoluminescent Properties of the Cu(I)/X/α,ω-Bis(benzotriazole)alkane Hybrid Family (X = Cl, Br, I, and CN)

This work focused on a systematic investigation of the influences of the spacer length of the flexible alpha,omega-bis(benzotriazole)alkane ligands and counteranions on the overall molecular architectures of hybrid structures that include Cu(I). Using the self-assembly of CuX (X = Cl, Br, I, or CN) with the five structurally related flexible organic ligands (L1-L5) under hydro(solvo)thermal conditions, we have synthesized and characterized 10 structurally unique materials of the Cu(I)/X/alpha,omega-bis(benzotriazole)alkane organic-inorganic hybrid family, {[CuCl](2)(L1)}(n) (1), {[CuBr](L2)}(n) (2), {[CuCl](2)(L3)}(n) (3), {[CuI](2)(L4)}(n) (4), {[CuBr](2)(L4)}(n) (5), {[CuBr](3)(L5)}(n) (6), {[CuCN](2)(L1)}(n) (7), {[CuCl](4)(L2)}(n) (8), {[CuBr](4)(L2)}(n) (9), and {[CuCl](2)(L4)}(n) (10), by means of elemental analyses, X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and photoluminescence measurements. Single-crystal X-ray analyses showed that the inorganic subunits in these compounds were {Cu(2)X(2)} binuclear clusters (1 and 2), {Cu(4)X(4)} cubane clusters (4, 5, and 10), {CuX}(n) single chains (3 and 7), a {Cu(3)X(3)}(n) ladderlike chain (6), and unprecedented {Cu(8)X(8)}(n) ribbons (8 and 9). The increasing dimensionality from 1-D (1-4) to 2-D (5 and 6) to 3-D (7-10) indicates that the spacer length and isomerism of the bis(benzotriazole)alkane ligands play an essential role in the formation of the framework of the Cu(I) hybrid materials. The influence of counteranions and pi-pi stacking interactions on the formation and dimensionality of these hybrid coordination polymers has also been explored. In addition, all the complexes exhibit high thermal stability and strong fluorescence properties in the solid state at ambient temperature.

Two Zeolite-Type Frameworks in One Metal–Organic Framework with Zn24@Zn104 Cube-in-Sodalite Architecture†

Two in one: A metal-organic framework obtained from three different inorganic building blocks (tetrameric Zn(4) O, trimeric Zn(3) OH, and monomeric Zn) posseses a nested cage-in-cage and framework-in-framework architecture. 24 Zn(4) O tetramers and eight Zn monomers form a sodalite cage into which a cubic cage made from eight Zn(3) (OH) trimers is nestled. Eight monomeric Zn(2+) centers interconnect these two cages.

Framework Cationization by Preemptive Coordination of Open Metal Sites for Anion-Exchange Encapsulation of Nucleotides and Coenzymes.

Cationic frameworks can selectively trap anions through ion exchange, and have applications in ion chromatography and drug delivery. However, cationic frameworks are much rarer than anionic or neutral ones. Herein, we propose a concept, preemptive coordination (PC), for targeting positively charged metal-organic frameworks (P-MOFs). PC refers to proactive blocking of metal coordination sites to preclude their occupation by neutralizing ligands such as OH(-) . We use 20 MOFs to show that this PC concept is an effective approach for developing P-MOFs whose high stability, porosity, and anion-exchange capability allow immobilization of anionic nucleotides and coenzymes, in addition to charge- and size-selective capture or separation of organic dyes. The CO2 and C2 H2 uptake capacity of 117.9 cm(3)  g(-1) and 148.5 cm(3)  g(-1) , respectively, at 273 K and 1 atm, is exceptionally high among cationic framework materials.

Induction of trimeric [Mg3(OH)(CO2)6] in a porous framework by a desymmetrized tritopic ligand

The use of a desymmetrized tritopic ligand with both carboxyl and pyridyl functionalities leads to the first occurrence of the [Mg(3)(μ(3)-OH)(CO(2))(6)] trimer as the 3-D framework building block in a porous crystal that shows relatively high H(2) uptake (1.37% at 77 K and 1 atm).

(3,4)-Connected jph-type porous framework with Cu4I4clusters as jointing points of helices

A (3,4)-connected jph-type porous framework with Cu4I4clusters as jointing points of helices has been solvothermally synthesized and characterized; it shows alternating left- and right-handed helices structure, featuring an unprecedented non-interpenetrated jph network with high degree of porosity and large open channels.

Design of Pore Size and Functionality in Pillar-Layered Zn-Triazolate-Dicarboxylate Frameworks and Their High CO2/CH4 and C2 Hydrocarbons/CH4 Selectivity.

In the design of new materials, those with rare and exceptional compositional and structural features are often highly valued and sought after. On the other hand, materials with common and more accessible modes can often provide richer and unsurpassed compositional and structural variety that makes them a more suitable platform for systematically probing the composition-structure-property correlation. We focus here on one such class of materials, pillar-layered metal-organic frameworks (MOFs), because different pore size and shape as well as functionality can be controlled and adjusted by using pillars with different geometrical and chemical features. Our approach takes advantage of the readily accessible layered Zn-1,2,4-triazolate motif and diverse dicarboxylate ligands with variable length and functional groups, to prepare seven Zn-triazolate-dicarboxylate pillar-layered MOFs. Six different gases (N2, H2, CO2, C2H2, C2H4, and CH4) were used to systematically examine the dependency of gas sorption properties on chemical and geometrical properties of those MOFs as well as their potential applications in gas storage and separation. All of these pillar-layered MOFs show not only remarkable CO2 uptake capacity, but also high CO2 over CH4 and C2 hydrocarbons over CH4 selectivity. An interesting observation is that the BDC ligand (BDC = benzenedicarboxylate) led to a material with the CO2 uptake outperforming all other metal-triazolate-dicarboxylate MOFs, even though most of them are decorated with amino groups, generally believed to be a key factor for high CO2 uptake. Overall, the data show that the exploration of the synergistic effect resulting from combined tuning of functional groups and pore size may be a promising strategy to develop materials with the optimum integration of geometrical and chemical factors for the highest possible gas adsorption capacity and separation performance.