Pore Surface Engineering with Controlled Loadings of Functional Groups via Click Chemistry in Highly Stable Metal–Organic Frameworks

Synthesis of cobalt-, nickel-, copper-, and zinc-based, water-stable, pillared metal-organic frameworks

The performance of metal-organic frameworks (MOFs) in humid or aqueous environments is a topic of great significance for a variety of applications ranging from adsorption separations to gas storage. While a number of water-stable MOFs have emerged recently in the literature, the majority of MOFs are known to have poor water stability compared to zeolites and activated carbons, and there is therefore a critical need to perform systematic water-stability studies and characterize MOFs comprehensively after water exposure. Using these studies we can isolate the specific factors governing the structural stability of MOFs and direct the future synthesis efforts toward the construction of new, water-stable MOFs. In this work, we have extended our previous work on the systematic water-stability studies of MOFs and synthesized new, cobalt-, nickel-, copper-, and zinc-based, water-stable, pillared MOFs by incorporating structural factors such as ligand sterics and catenation into the framework. Stability is assessed by using water vapor adsorption isotherms along with powder X-ray diffraction patterns and results from BET modeling of N2 adsorption isotherms before and after water exposure. As expected, our study demonstrates that unlike the parent DMOF structures (based on Co, Ni, Cu, and Zn metals), which all collapse under 60% relative humidity (RH), their corresponding tetramethyl-functionalized variations (DMOF-TM) are remarkably stable, even when adsorbing more than 20 mmol of H2O/g of MOF at 80% RH. This behavior is due to steric factors provided by the methyl groups grafted on the BDC (benzenedicarboxylic acid) ligand, as shown previously for the Zn-based DMOF-TM. Moreover, 4,4',4″,4‴-benzene-1,2,4,5-tetrayltetrabenzoic acid based, pillared MOFs (based on Co and Zn metals) are also found to be stable after 90% RH exposure, even when the basicity of the bipyridyl-based pillar ligand is low. This is due to the presence of catenation in their frameworks, similar to MOF-508 (Zn-BDC-BPY), which has also been reported to be stable after exposure to 90% RH.

Enhanced uptake and selectivity of CO(2) adsorption in a hydrostable metal-organic frameworks via incorporating methylol and methyl groups

A new methylol and methyl functionalized metal-organic frameworks (MOFs) QI-Cu has been designed and synthesized. As a variant of NOTT-101, this material exhibits excellent CO2 uptake capacities at ambient temperature and pressure, as well as high CH4 uptake capacities. The CO2 uptake for QI-Cu is high, up to 4.56 mmol g(-1) at 1 bar and 293 K, which is top-ranked among MOFs for CO2 adsorption and significantly larger than the nonfunctionalized NOTT-101 of 3.93 mmol g(-1). The enhanced isosteric heat values of CO2 and CH4 adsorption were also obtained for this linker functionalized MOFs. From the single-component adsorption isotherms, multicomponent adsorption was predicted using the ideal adsorbed solution theory (IAST). QI-Cu shows an improvement in adsorptive selectivity of CO2 over CH4 and N2 below 1 bar. The incorporation of methylol and methyl groups also greatly improves the hydrostability of the whole framework.

Imparting biomolecules to a metal-organic framework material by controlled DNA tetrahedron encapsulation

Recently, the incorporation of biomolecules in Metal-organic frameworks (MOFs) attracts many attentions because of controlling the functions, properties and stability of trapped molecules. Although there are few reports on protein/MOFs composites and their applications, none of DNA/MOFs composite is reported, as far as we know. Here, we report a new composite material which is self-assembled from 3D DNA (guest) and pre-synthesized MOFs (host) by electrostatic interactions and hydrophilic interactions in a well-dispersed fashion. Its biophysical characterization is well analyzed by fluorescence spectroscopy, quartz crystal microbalance (QCM) and transmission electron microscopy (TEM). This new composite material keeps 3D DNA nanostructure more stable than only 3D DNA nanostructure in DI water at room temperature, and stores amounts of genetic information. It will make DNA as a guest for MOFs and MOFs become a new platform for the development of DNA nanotechnology.

Alkylamine-tethered stable metal-organic framework for CO(2) capture from flue gas

Different alkylamine molecules were post-synthetically tethered to the unsaturated Cr(III) centers in the metal-organic framework MIL-101. The resultant metal-organic frameworks show almost no N2 adsorption with significantly enhanced CO2 capture under ambient conditions as a result of the interaction between amine groups and CO2 molecules. Given the extraordinary stability, high CO2 uptake, ultrahigh CO2 /N2 selectivity, and mild regeneration energy, MIL-101-diethylenetriamine holds exceptional promise for post-combustion CO2 capture and CO2 /N2 separation.

A porous sodalite-type MOF based on tetrazolcarboxylate ligands and [Cu4Cl]7+ squares with open metal sites for gas sorption

A porous sodalite-type metal-organic framework based on tetrazolcarboxylate ligands and [Cu4Cl](7+) squares was successfully synthesized, which exhibited permanent porosity and high adsorption abilities of H2, CO2 and organic chemical pollutants.

Metal–organic frameworks as heterogeneous photocatalysts: advantages and challenges

The use of metal organic frameworks as photocatalysts is critically reviewed and their main advantages and challenges are evaluated.

Recent advances in the design strategies for porphyrin-based coordination polymers

Strategies to construct the porphyrin-based coordination polymers are summarized based on utilization of metal nodes, porphyrin ligands, inorganic polyoxometalates and post-synthetic modification.

Substitution reactions in metal–organic frameworks and metal–organic polyhedra

This review summarizes the advances in the study of substitution reactions in metal–organic frameworks (MOFs) and metal–organic polyhedra (MOPs).

An ultrastable, flexible POM-based coordination polymer with redox properties

A new porous coordination polymer (1) has been prepared under hydrothermal conditions. The flexible framework of1shows dynamic behavior accompanied with the removal/adsorption of guest water molecules. Remarkably, crystals of1can remain intact even in 8 mol L⁻¹hydrochloric acid, dilute NaOH solution (pH = 12) and boiling water.

High CO2/N2 and CO2/CH4 selectivity in a chiral metal–organic framework with contracted pores and multiple functionalities

A MOF with contracted pores and multiple functionalities showing high selectivities on CO₂/N₂ and CO₂/CH₄ gas mixtures was constructed.

Luminescent metal–organic frameworks for chemical sensing and explosive detection

This review provides an update on the photoluminescence properties of LMOFs and their utility in chemical sensing and explosive detection.

A molecular porous zirconium–organic material exhibiting highly selective CO2 adsorption, high thermal stability, reversible hydration, facile ligand exchange and exclusive dimerization of phenylacetylene

A multi-functional molecular porous zirconium-organic material, CAUMOF-12, has been discovered.

Metal–organic frameworks with improved moisture stability based on a phosphonate monoester: effect of auxiliary N-donor ligands on framework dimensionality

A series of metal–organic frameworks (MOFs) with improved moisture stability based on a phosphonate monoester, featuring 1D chains, 2D layers and 3D networks, have been obtained in the presence of auxiliary N-donor ligands.

Nanomaterials for membrane fouling control: accomplishments and challenges

We report a review of recent research efforts on incorporating nanomaterials-including metal/metal oxide nanoparticles, carbon-based nanomaterials, and polymeric nanomaterials-into/onto membranes to improve membrane antifouling properties in biomedical or potentially medical-related applications. In general, nanomaterials can be incorporated into/onto a membrane by blending them into membrane fabricating materials or by attaching them to membrane surfaces via physical or chemical approaches. Overall, the fascinating, multifaceted properties (eg, high hydrophilicity, superparamagnetic properties, antibacterial properties, amenable functionality, strong hydration capability) of nanomaterials provide numerous novel strategies and unprecedented opportunities to fully mitigate membrane fouling. However, there are still challenges in achieving a broader adoption of nanomaterials in the membrane processes used for biomedical applications. Most of these challenges arise from the concerns over their long-term antifouling performance, hemocompatibility, and toxicity toward humans. Therefore, rigorous investigation is still needed before the adoption of some of these nanomaterials in biomedical applications, especially for those nanomaterials proposed to be used in the human body or in contact with living tissue/body fluids for a long period of time. Nevertheless, it is reasonable to predict that the service lifetime of membrane-based biomedical devices and implants will be prolonged significantly with the adoption of appropriate fouling control strategies.

Metal-organic frameworks based on previously unknown Zr8/Hf8 cubic clusters

The ongoing study of zirconium- and hafnium-porphyrinic metal-organic frameworks (MOFs) led to the discovery of isostructural MOFs based on Zr8 and Hf8 clusters, which are unknown in both cluster and MOF chemistry. The Zr8O6 cluster features an idealized Zr8 cube, in which each Zr atom resides on one vertex and each face of the cube is capped by one μ4-oxygen atom. On each edge of the cube, a carboxylate from a porphyrinic ligand bridges two Zr atoms to afford a 3D MOF with a very rare (4,12)-connected ftw topology, in which two types of polyhedral cages with diameters of ∼1.1 and ∼2.0 nm and a cage opening of ∼0.8 nm are found. The isostructural Zr- and Hf-MOFs exhibit high surface areas, gas uptakes, and catalytic selectivity for cyclohexane oxidation.

An exceptionally stable, porphyrinic Zr metal-organic framework exhibiting pH-dependent fluorescence

A reaction between a Zr(IV) salt and a porphyrinic tetracarboxylic acid leads to a metal-organic framework (MOF) with two types of open channels, representing a MOF featuring a (4,8)-connected sqc net. The MOF remains intact in both boiling water and aqueous solutions with pH ranging from 1 to 11, a remarkably extensive pH range that a MOF can sustain. Given its exceptional stability and pH-dependent fluorescent intensity, the MOF can potentially be applied in fluorescent pH sensing.