Trevor A. Makal

A Highly Porous and Robust (3,3,4)‐Connected Metal–Organic Framework Assembled with a 90° Bridging‐Angle Embedded Octacarboxylate Ligand

In general, MOF structures may be viewed as having two main components: the organic linker and the inorganic metal cluster (also known as secondary building unit, SBU). It is well-established that the combination of both components governs the final framework topology, which in turn determines the performance as a storage or separation medium. The dinuclear paddle-wheel cluster, a square building unit, is one of the commonly used SBUs in the isoreticular synthesis of MOFs owing to its ability to form innumerous structures with a large range of organic ligands. We are particularly interested in the dicopper(II) paddle-wheel cluster because of its enhanced moisture resistance over the Zn4O cluster [3] and genesis of exposed metal sites after the removal of axially coordinated solvent molecules. The presence of open metal sites in the framework facilitates H2 storage owing to the strong metal–H2 interaction. [4]

RECENT ADVANCES IN THE STUDY OF MESOPOROUS METAL-ORGANIC FRAMEWORKS

Metal–organic frameworks (MOFs), which consist of metal ions or clusters and organic bridging ligands, have recently emerged as an important family of porous materials. In this comment, we discuss the current state of the field pertaining to MOFs with pore sizes between 2 and 50 nm, which have great application potential in gas storage, separation, sensor, catalysis, and drug delivery. This review will cover mesoporous MOFs containing 3-D channels, 1-D channels, and large cavities, as well as those based on supramolecular templates.

Construction of two 3D homochiral frameworks with 1D chiral pores via chiral recognition.

The reactions of a pair of enantiomers of macrocyclic nickel(II) complexes with racemic penicillamine generated two 3D hydrogen-bonded homochiral frameworks of {[Ni(f-(SS)-L)](2)(l-pends)(ClO(4))(2)}(n) (Λ-1) and {[Ni(f-(RR)-L)](2)(d-pends) (ClO(4))(2)}(n) (Δ-1). The frameworks possess 1D tubular pores and opposite right/left-handed helical porous surfaces (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; pends(2-) = penicillaminedisulfide anion).

Protein Immobilization in Metal–Organic Frameworks by Covalent Binding

Metal–organic frameworks (MOFs), possessing a well defined system of pores, demonstrate extensive potential serving as a platform in biological catalysis. Successful immobilization of enzymes in a MOF system retains the enzymatic activity, renders the active site more accessible to the substrate, and promises recyclability for reuse, and solvent adaptability in a broad range of working conditions. This highlight describes enzyme immobilization on MOFs via covalent binding and its significance.

Realization of both high hydrogen selectivity and capacity in a guest responsive metal–organic framework

Two newly designed semi-flexible tetratopic carboxylate ligands, 5′,5′′′′-(propane-2,2-diyl)bis(2′-methoxy-[1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylate) (pbtd-OMe4−) and 5′,5′′′′-(propane-2,2-diyl)bis(2′-ethoxy-[1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylate) (pbtd-OEt4−), have been used to connect dicopper paddlewheel building units to afford two isostructural metal–organic frameworks, Cu2(H2O)2(pbtd-OR)·xS (R = Me, PCN-38·xS; R = Et, PCN-39·xS, S represents noncoordinated guest molecules, PCN = porous coordination network) with novel structure and gas sorption properties upon activation. PCN-39 undergoes structural transformations upon guest solvent removal, leading to observation of distinct phases from in situ powder X-ray diffraction measurements, and exhibits selective adsorption of H2 (up to 2.0 wt%) over CO, CO2, and N2, which can be explained by optimized space-filling of the pendant ethoxy group. PCN-38 undergoes no transformation upon activation and exhibits hydrogen uptake up to 2.2 wt%, as well as moderate uptake of other gases. The selective adsorption of hydrogen over other gases highlights the potential application of PCN-39 in industrially important gas separation.