Understanding the molecular details of CO(2)-sorbent interactions is critical for the design of better carbon-capture systems. Here we report crystallographic resolution of CO(2) molecules and their binding domains in a metal-organic framework functionalized with amine groups. Accompanying computational studies that modeled the gas sorption isotherms, high heat of adsorption, and CO(2) lattice positions showed high agreement on all three fronts. The modeling apportioned specific binding interactions for each CO(2) molecule, including substantial cooperative binding effects among the guest molecules. The validation of the capacity of such simulations to accurately model molecular-scale binding bodes well for the theory-aided development of amine-based CO(2) sorbents. The analysis shows that the combination of appropriate pore size, strongly interacting amine functional groups, and the cooperative binding of CO(2) guest molecules is responsible for the low-pressure binding and large uptake of CO(2) in this sorbent material.

A hydrophobic CO 2 physisorbent Most materials for carbon dioxide (CO 2 ) capture of fossil fuel combustion, such as amines, rely on strong chemisorption interactions that are highly selective but can incur a large energy penalty to release CO 2 . Lin et al . show that a zinc-based metal organic framework material can physisorb CO 2 and incurs a lower regeneration penalty. Its binding site at the center of the pores precludes the formation of hydrogen-bonding networks between water molecules. This durable material can preferentially adsorb CO2 at 40% relative humidity and maintains its performance under flue gas conditions of 150°C. —PDS

A metal organic framework with amine-lined pores gives high values for surface area and heat of adsorption with CO(2) gas.

A new porous metal-organic framework (MOF), barium tetraethyl-1,3,6,8-pyrenetetraphosphonate (CALF-25), which contains a new phosphonate monoester ligand, was synthesized through a hydrothermal method. The MOF is a three-dimensional structure containing 4.6 Å × 3.9 Å rectangular one-dimensional pores lined with the ethyl ester groups from the ligand. The presence of the ethyl ester groups makes the pores hydrophobic in nature, as determined by the low heats of adsorption of CH(4), CO(2), and H(2)O (14.5, 23.9, and 45 kJ mol(-1), respectively) despite the polar and acidic barium phosphonate ester backbone. The ethyl ester groups within the pores also protect CALF-25 from decomposition by water vapor, with crystallinity and porosity being retained after exposure to harsh humid conditions (90% relative humidity at 353 K). The use of phosphonate esters as linkers for the construction of MOFs provides a method to protect hydrolytically susceptible coordination backbones through kinetic blocking.

Synthetic porous materials, that is, carbon materials, inorganic solids, and coordination polymers (or metal-organic frameworks, MOFs), have been a focus of research for the past few decades, with the goal of enhancing the properties of naturally occurring porous materials (zeolites), which have made a remarkable impact on human society and the environment. [1][2][3] In more recent times, the focus has shifted towards expanding the applications of synthetic porous metal-organic materials, in particular for gas (i.e., hydrogen, methane, and carbon dioxide) and solvent storage, with promising results. [2,4,5] Herein we show that discrete metallo-supramolecular materials, as opposed to infinite polymeric systems (including MOFs), are a viable class of porous material for gas and solvent storage.[6] In a recent report we showed the magnetic switching function of a nanoball (Fe-nano).[7] Herein we highlight the versatility of this system through systematic metal and anion variation to form six new analogues of the Figure 1). Furthermore, we demonstrate that the properties of this general system can be extended from magnetic switching to gas and solvent storage, to create a truly multifunctional system. Through parallel thermogravimetric, powder X-ray diffraction, and nitrogen sorption analysis we show that Cu-nano is structurally stable to guest desorption, a property more commonly associated with porous framework materials. Coordinatively unsaturated, accessible Cu II sites are created in this desolvation process, which are of interest for their ability to bind hydrogen gas; it has been shown in a number of nanoporous framework materials that the affinity of hydrogen gas to a surface is greatly increased with the presence of such open metal sites. [5,8,9] Furthermore, using electron paramagnetic resonance (EPR) spectroscopy, we follow the guest exchange and nanostructure functionalization for a range of organic solvents at these bare metal sites.When utilizing the self-assembly process to construct complex inorganic materials, small variations in synthetic conditions (i.e., metal, pH value, temperature, time, concentration, solvent, anion) often result in large variations in structure and topology; thus, the successful production of families of analogous polymeric (and discrete cage) materials containing different metals is uncommon.[10] The successful synthesis of this family of analogous discrete materials is largely due to the tailored design features of the bifunctional organic ligand [Tp 4-py ] À (tris[3-(4'-pyridyl)pyrazol-1-yl]hydroborate)) and, in particular, to the formation in situ of an intermediate metalloligand building block [Cu I (Tp 4-py )-(MeCN)], as outlined in our structural and magnetic report of Fe-nano.[7] Specifically, with the addition of Cu I to form this metalloligand, the otherwise flexible organic unit is made structurally rigid, and the directionality of the peripheral pyridyl donor groups is effectively locked in. (Figure 1). The structure of each of these species has been confirmed by ...