There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

J. Appl. Cryst.の発刊に際して

The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.

/pdf/reticular-synthesis-and-the-design-of-new-materials-lazbx7tdux.pdf

Reticular synthesis and the design of new materials

Metal–Organic Frameworks (MOFs) and Coordination Polymers

Two-dimensional (2D) π-conjugated conductive metal–organic frameworks (cMOFs, 2DπcMOF) with modulated channel sizes and a broad conductivity range have been reported in the last decade. In contrast, the corresponding comparative studies on their effects on chemiresistive sensing performances, which measure the resistive response toward external chemical stimuli, have not yet been reported. In this work, we sought to explore the structure–performance relationships of honeycomb-like 2D π-conjugated cMOF chemiresistive gas sensors with channel sizes less than 2 nm (the mass transport issue) and broad conductivity in the range from ∼10−8 S cm−1 to 1 S cm−1 (the charge transport issue). As a result, we found that the cMOF with a lower conductivity facilitates the much more sensitive response toward the charge transfer of the adsorbed gases (relative increases in resistance: R = 63.5% toward 100 ppm of NH3 for the as prepared Cu–THQ sensor with the conductivity of ∼10−8 S cm−1). Interestingly, the cMOF with a medium channel size (Cu–THHP–THQ) exhibited the fastest response speed in sensing, although it contains H2en2+ as neutralizing counterions in the channels. From the evaluation of the pore size distribution, it is found that the overall porosity (meso- & micro-pores) of cMOFs, rather than the pore size of the honeycomb structure, would determine their sensing speed. When comparing the performance of two different morphologies of nanorods (NRs) and nanosheets (NSs), NRs showed a slower response and extended recovery time, which can be ascribed to the slower gas diffusion in the more extended 1D channel. Altogether, our results demonstrate the first systematic studies on the effect of various structural parameters on the chemiresistive sensor performance of cMOFs.

https://pubs.rsc.org/en/content/articlepdf/2021/dt/d1dt02323c

A comparative study of honeycomb-like 2D π-conjugated metal-organic framework chemiresistors: conductivity and channels.

The chemistry of coordination polymers has been extensively advanced in recent decades, producing various architectures that are rationally constructed from a variety of molecular building blocks and interactions between them. Researchers have worked to create a diverse range of coordination frameworks and have raised the structural chemistry to a mature level. The next challenge is to explore their chemical and physical functionalities, which are associated with the microporous properties of frameworks. This review focuses on crystal structures and microporous properties of coordination polymers containing organic N-containing heterocyclic molecules as bridging ligands.

Coordination Polymers Constructed from Transition Metal Ions and Organic N‐Containing Heterocyclic Ligands: Crystal Structures and Microporous Properties

Die Anionen PF6−und CF3SO3− werden von der neuen radikalischen Wirtverbindung [(Cu-dppe)3{hat-(CN)6}]2 +, die in einer Eintopfreaktion aus einer Kupfer(I)-Verbindung, hat-(CN)6 und dppe in Aceton synthetisiert wurde, komplexiert. Die Wirt/Gast-Komplexe wurden sowohl in Losung als auch im festen Zustand charakterisiert (siehe Bild; A−: PF6−, CF3SO3−). hat-(CN)6 = Hexaazatriphenylen-hexacarbonitril; dppe = 1,2-Bis(diphenylphosphanyl)ethan.

Susumu Kitagawa

Papers

Metal–Organic Frameworks (MOFs) and Coordination Polymers

A comparative study of honeycomb-like 2D π-conjugated metal-organic framework chemiresistors: conductivity and channels.

Coordination Polymers Constructed from Transition Metal Ions and Organic N‐Containing Heterocyclic Ligands: Crystal Structures and Microporous Properties

Ein neuer radikalischer Wirt für Anionen: [(Cu-dppe)3{hat-(CN)6}]2 +

Hydrogen-bonding assemblies constructed from metalloligand building blocks and H2O