A Robust Nanoporous Supramolecular Metal–Organic Framework Based on Ionic Hydrogen Bonds

Hydrogen‐bond assembly of tripod‐like organic cations [H₃‐MeTrip]³⁺ (1,2,3‐tri(4′‐pyridinium‐oxyl)‐2‐methylpropane) and the hexa‐anionic complex [Zr₂(oxalate)₇]^6? leads to a structurally, thermally, and chemically robust porous 3D supramolecular framework showing channels of 1 nm in width. Permanent porosity has been ascertained by analyzing the material at the single‐crystal level during a sorption cycle. The framework crystal structure was found to remain the same for the native compound, its activated phase, and after guest resorption. The channels exhibit affinities for polar organic molecules ranging from simple alcohols to aniline. Halogenated molecules and I₂ are also taken up from hexane solutions by this unique supramolecular framework.     

A Coordination Network Featuring Two Distinct Copper(II) Coordination Environments for Highly Selective Acetylene Adsorption

Single crystals of 2D coordination network {Cu₂ L ₂ ⋅ (DMF)₃(H₂O)₃}_n ( 1-DMF ) were prepared by reaction of commercial reagents 3-formyl-4-hydroxybenzoic acid (H₂ L ) and Cu(NO₃)₂ in dimethylformamide (DMF). The single-crystal structure shows two distinct Cu(II) coordination environments arising from the separate coordination of Cu(II) cations to the carboxylate and salicylaldehydato moieties on the linker, with 1D channels running through the structure. Flexibility is exhibited on solvent exchange with ethanol and tetrahydrofuran, while porosity and the unique overall connectivity of the structure are retained. The activated material exhibits type I gas sorption behaviour and a BET surface area of 950 m² g⁻¹ (N₂, 77 K). Notably, the framework adsorbs negligible quantities of CH₄ compared with CO₂ and the C₂H_n hydrocarbons. It exhibits exceptional selectivity for C₂H₂/CH₄ and C₂H₂/C₂H_n, which has applicability in separation technologies for the isolation of C₂H₂.     

Modulation of the Sorption Characteristics for an H-bonded porous Architecture by Varying the Chemical Functionalization of the Channel Walls

Five isostructural microporous supramolecular architectures prepared by H-bonded assembly between the hexa-anionic complex [Zr₂(Ox)₇]⁶⁻ (Ox=oxalate, (C₂O₄)²⁻) and tripodal cations (H₃-TripCH₂-R)³⁺ with R=H, CH₃, OH and OBn (Bn=CH₂Ph) are reported. The possibility to obtain the same structure using a mixture of tripodal cations with different R group (R=OH and R=CH₃) has also been successfully explored, providing a unique example of three-component H-bonded porous framework. The resulting SPA-1(R) materials feature 1D pores decorated by R groups, with apparent pore diameters ranging from 3.0 to 8.5 Å. Influence of R groups on the sorption properties of these materials is evidenced through CO₂ and H₂O vapor sorption/desorption experiments, as well as with I₂ capture/release experiments in liquid media. This study is one of the first to demonstrate the possibility of tuning the porosity and exerting precise control over the chemical functionalization of the pores in a given H-bonded structure, without modifying the topology of the reference structure, and thus finely adjusting the sorption characteristics of the material.     

Microporous organic materials from hydrophobic dipeptides

In the last few years dipeptides with two hydrophobic residues (hydrophobic dipeptides) have emerged as an unexpected source of stable microporous organic materials. Supramolecular self-assembly of the rather small building blocks is dictated by stringent demands on the hydrogen-bond formation by the peptide main chains and the aggregation of hydrophobic entities in the side chains. A systematic survey of structures derived from single-crystal X-ray diffraction studies has revealed the existence of two large classes of structures, differing in the dimensionality of the hydrogen-bonding patterns in the crystals and the nature of the channels. The present review summarizes the structural properties of the microporous dipeptides and discusses their potential applications.     

Nonclassical Tunability of Solid‐State CD and CPL Properties of a Chiral 2‐Naphthalenecarboxylic Acid/Amine Supramolecular Organic Fluorophore

The solid‐state chiral optical properties (circular dichroism and circularly polarized luminescence) of a 2‐naphthalenecarboxylic acid/amine supramolecular organic fluorophore can be controlled by changing the aryl unit of the chiral 1‐arylethylamine component of the molecule rather than altering the chirality of the 1‐arylethylamine itself.     

A Toroidal Zr70 Oxysulfate Cluster and Its Diverse Packing Structures

Herein, we report the discovery of a toroidal inorganic cluster of zirconium(IV) oxysulfate of unprecedented size with the formula Zr₇₀(SO₄)₅₈(O/OH)₁₄₆⋅x(H₂O) (Zr₇₀), which displays different packing of ring units and thus several polymorphic crystal structures. The ring measures over 3 nm across, has an inner cavity of 1 nm and displays a pseudo-10-fold rotational symmetry of Zr₆ octahedra bridged by an additional Zr in the outer rim of the ring. Depending on the co-crystallizing species, the rings form various crystalline phases in which the torus units are connected in extended chain and network structures. One phase, in which the ring units are arranged in layers and form one-dimensional channels, displays high permanent porosity (BET surface area: 241 m² g⁻¹), and thus demonstrates a functional property for potential use in, for example, adsorption or heterogeneous catalysis.     

Construction of hydrogen-bonded ternary organic crystals derived from L-tartaric acid and their application to enantioseparation of secondary alcohols

Ternary organic crystals consisting of an L-tartaric acid-derived dicarboxylic acid, a commercially available achiral diamine, and a chiral secondary alcohol have been developed and characterized by X-ray crystallography. 1D, 2D, and 3D hydrogen-bonded supramolecular networks were constructed, depending on the structure of the diamine used. Benzylic and aliphatic secondary alcohols were enantioselectively incorporated into the crystal and were successfully enantioseparated with up to 86 and 79% enantiomeric excess (ee), respectively. Selective incorporation of one enantiomer of 2-butanol, which is a small chiral aliphatic alcohol, was achieved by the cooperative effects of hydrogen bonds, CH···π interactions, and van der Waals interactions between the guest and host molecules, with the aid of two water molecules. The high host potential of the binary supramolecular system is mainly attributed to the skewed conformation of two rigid aromatic groups of tartaric acid derivatives, which prevents dense packing of the molecules and enhances the formation of multicomponent inclusion crystals.     

Molecular organic crystals: from barely porous to really porous

Holey suitable crystals: A trisbenzimidazolone molecule self-assembles by hydrogen bonding to form a permanently porous crystal with an apparent surface area, SA(BET) , of 2796?m(2) g(-1) , demonstrating that extrinsic, intermolecular porosity is a viable strategy for highly porous materials.     

Nanoporous Carbons: Looking Beyond Their Perception as Adsorbents,Catalyst Supports and Supercapacitors

The discovery of carbon nanoforms, and especially graphene, has opened up new directions of science and technology. Many applications are based on the unique properties of graphene, such as its high electrical and thermal conductivity, strength, flexibility, photoactivity and transparency. Inspired by the emerging graphene science, we directed our efforts to the exploration of new applications of nanoporous (microporous) carbons. Their matrix is built of distorted graphene layers, between which pores with sizes ranging from a fraction of a nanometer to hundreds of nanometers exist. This is a very unique feature of nanoporous carbons resulting in their developed surface areas. Moreover, there are vast possibilities to modify the surface chemistry of carbons and thus their surface properties. Even though the traditional applications of porous carbons focus mainly on adsorption and separation, we decided to explore them as photocatalysts, oxygen reduction catalysts and sensors. Related to their visible‐light activity, their possible application in solar energy harvesting is also indicated. This Personal Account presents our paths leading to the exploration of these directions, describing the results collected and difficulties encountered, along with the challenges remaining to be addressed.

     

Molecular and Supramolecular Networks on Surfaces: From Two‐Dimensional Crystal Engineering to Reactivity

The invention of the scanning tunneling microscope has led to the visualization of molecules in real space on atomically flat conductive substrates. This has boosted research into supramolecular chemistry on surfaces. In this Review, we highlight recent developments in the design and functionality of supramolecular surface patterns, with special attention paid to those networks which are chiral or contain a high degree of porosity as well as to the reactivity, which is one of the most important recent developments in supramolecular surface chemistry.