A Reusable MOF‐Supported Single‐Site Zinc(II) Catalyst for Efficient Intramolecular Hydroamination of o ‐Alkynylanilines

Tuning the Stereoselectivity of an Intramolecular Aldol Reaction by Precisely Modifying a Metal-Organic Framework Catalyst

We report the catalysis of an enantioselective, intramolecular aldol reaction accelerated by an organocatalyst embedded in a series of multicomponent metal-organic frameworks. By precisely programming the pore microenvironment around the site of catalysis, we show how important features of an intramolecular aldol reaction can be tuned, such as the substrate consumption, enantioselectivity, and degree of dehydration of the products. This tunability arises from non-covalent interactions between the reaction participants and modulator groups that occupy positions in the framework remote from the catalytic site. Further, the catalytic moiety can be switched form one framework linker to another. Deliberately building up microenvironments that can influence the outcome of reaction processes in this way is not possible in conventional homogenous catalysts but is reminiscent of enzymes.

A "Thermodynamically Stable" 2D Nickel Metal-Organic Framework over a Wide pH Range with Scalable Preparation for Efficient C2 s over C1 Hydrocarbon Separations

The design and construction of "thermodynamically stable" metal-organic frameworks (MOFs) that can survive in liquid water, boiling water, and acidic/basic solutions over a wide pH range is highly desirable for many practical applications, especially adsorption-based gas separations with obvious scalable preparations. Herein, a new thermodynamically stable Ni MOF, {[Ni(L)(1,4-NDC)(H₂ O)₂ ]}_n (IITKGP-20; L=4,4'-azobispyridine; 1,4-NDC=1,4-naphthalene dicarboxylic acid; IITKGP stands for the Indian Institute of Technology Kharagpur), has been designed that displays moderate porosity with a BET surface area of 218 m²  g^-1 and micropores along the [10-1] direction. As an alternative to a cost-intensive, cryogenic, high-pressure distillation process for the separation of hydrocarbons, MOFs have recently shown promise for such separations. Thus, towards an application standpoint, this MOF exhibits a higher uptake of C₂ hydrocarbons over that of C₁ hydrocarbon under ambient conditions, with one of the highest selectivities based on the ideal adsorbed solution theory (IAST) method. A combination of two strategies (the presence of stronger metal-N coordination of the spacer and the hydrophobicity of the aromatic moiety of the organic ligand) possibly makes the framework highly robust, even stable in boiling water and over a wide range of pH 2-10, and represents the first example of a thermodynamically stable MOF displaying a 2D structural network. Moreover, this material is easily scalable by heating the reaction mixture at reflux overnight. Because such separations are performed in the presence of water vapor and acidic gases, there is a great need to explore thermodynamically stable MOFs that retain not only structural integrity, but also the porosity of the frameworks.