Adsorptive separation is very important in industry. Generally, the process uses porous solid materials such as zeolites, activated carbons, or silica gels as adsorbents. With an ever increasing need for a more efficient, energy-saving, and environmentally benign procedure for gas separation, adsorbents with tailored structures and tunable surface properties must be found. Metal–organic frameworks (MOFs), constructed by metal-containing nodes connected by organic bridges, are such a new type of porous materials. They are promising candidates as adsorbents for gas separations due to their large surface areas, adjustable pore sizes and controllable properties, as well as acceptable thermal stability. This critical review starts with a brief introduction to gas separation and purification based on selective adsorption, followed by a review of gas selective adsorption in rigid and flexible MOFs. Based on possible mechanisms, selective adsorptions observed in MOFs are classified, and primary relationships between adsorption properties and framework features are analyzed. As a specific example of tailor-made MOFs, mesh-adjustable molecular sieves are emphasized and the underlying working mechanism elucidated. In addition to the experimental aspect, theoretical investigations from adsorption equilibrium to diffusion dynamics via molecular simulations are also briefly reviewed. Furthermore, gas separations in MOFs, including the molecular sieving effect, kinetic separation, the quantum sieving effect for H2/D2 separation, and MOF-based membranes are also summarized (227 references).

Selective gas adsorption and separation in metal–organic frameworks

http://pubs.acs.org/doi/pdf/10.1021/cr300014x

Introduction to Metal–Organic Frameworks

Luminescent Functional Metal–Organic Frameworks

New materials capable of storing hydrogen at high gravimetric and volumetric densities are required if hydrogen is to be widely employed as a clean alternative to hydrocarbon fuels in cars and other mobile applications. With exceptionally high surface areas and chemically-tunable structures, microporous metal–organic frameworks have recently emerged as some of the most promising candidate materials. In this critical review we provide an overview of the current status of hydrogen storage within such compounds. Particular emphasis is given to the relationships between structural features and the enthalpy of hydrogen adsorption, spectroscopic methods for probing framework–H2 interactions, and strategies for improving storage capacity (188 references).

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Hydrogen storage in metal–organic frameworks

Metal–organic frameworks (MOFs) display a wide range of luminescent behaviors resulting from the multifaceted nature of their structure. In this critical review we discuss the origins of MOF luminosity, which include the linker, the coordinated metal ions, antenna effects, excimer and exciplex formation, and guest molecules. The literature describing these effects is comprehensively surveyed, including a categorization of each report according to the type of luminescence observed. Finally, we discuss potential applications of luminescent MOFs. This review will be of interest to researchers and synthetic chemists attempting to design luminescent MOFs, and those engaged in the extension of MOFs to applications such as chemical, biological, and radiation detection, medical imaging, and electro-optical devices (141 references).

Luminescent Metal–Organic Frameworks

Two 3d-4f heterometallic coordination polymers {[Ln(PDA)3Mn1.5(H2O)3].3.25H2O}infinity with 1D channels were synthesized under hydrothermal conditions (PDA = pyridine-2,6-dicarboxylic acid; Ln = Eu (1); Ln = Tb (2)). The emission intensities of 1 and 2 increased significantly upon addition of Zn2+, while the introduction of other metal ions caused the intensity to be either unchanged or weakened. The case implies that 1 and 2 may be used as luminescent probes of Zn2+.

Coordination Polymers Containing 1D Channels as Selective Luminescent Probes

A nanotubular 3D heterometallic zeolitic polymer, {[Yb(PDA)3Mn1.5(H2O)3]·1.5H2O}n (2), was designed and synthesized by simply tuning the amount of coordinated water on the Mn ion in the molecular ladder polymer {[Yb(PDA)3Mn1.5(H2O)6]·6H2O}n (1). 1 and 2 were structurally and magnetically characterized. The water molecules capsulated within the nanotube were arrayed into an unprecedented “water” pipe. The robust 2 retained intact networks after the removal of guest water trapped in the nanotubes and even after methanol replaced guest water.

Design and synthesis of 3d-4f metal-based zeolite-type materials with a 3D nanotubular structure encapsulated "water" pipe.

A nanotubular 3D coordination polymer based on a 3d-4f heterometallic assembly.

Two Dy-Mn polymers, {[Dy(L1)3Mn(1.5)(H2O)3]3.125H2O}n (1, L1 = pyridine-2,6-dicarboxylic acid) and {[Dy(L2)3Mn(1.5)(H2O)6]8.25H2O}n (2, L2 = 4-hydroxylpyridine-2,6-dicarboxylic acid), with high symmetry (S6) have been prepared. Polymer 1 has a nanoporous 3D framework with channel of about 17.6 A diameter, while 2 has a honeycomb-type 2D structure with the cavity of approximately 14.4 A diameter. In the construction of multidimensional porous polymers with 3d-4f mixed metals, it is the first observation that a ligand substituent effect leads to dramatic differences in the structures formed. Luminescent studies reveal that the emission intensities of 1 and 2 increase significantly upon the addition of Mg2+, whereas the introduction of other metal ions leaves the intensity unchanged or even weakens it; hence, both of them may serve as good candidates of Mg2+ luminescent probes. To our knowledge, complex 1 is also the first example of a 3d-4f metal-based nanoporous polymer to exhibit luminescent selectivity for Mg2+. Magnetic susceptibility measurements reveal a rather rare ferromagnetic interaction in 2. Thermal gravimetric analyses and powder X-ray diffraction investigations have also been performed, suggestive of high thermal stability of 1.

A Promising MgII‐Ion‐Selective Luminescent Probe: Structures and Properties of Dy–Mn Polymers with High Symmetry

3,5-Pyrazoledicarboxylic acid (H3L) reacts with nitrate salts of lanthanide(III) (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) under hydrothermal conditions to form a series of lanthanide polymers 1−9. These nine polymers have the same crystal system of monoclinic, but they exhibit three different kinds of metal−organic framework structures. The complexes {[Ln2(HL)3(H2O)4]·2H2O}n (Ln = Pr (1), Nd (2), and Sm (3)) were isostructural and exhibited porous 3D frameworks with a Cc space group. The complexes {[Ln2(HL)3(H2O)3]·3H2O}n (Ln = Eu (4), Gd (5), and Tb (6)) were isostructural and built 2D double-decker (2DD) frameworks with a P21/c space group. The complexes {[Ln(HL)(H2L)(H2O)2]}n ((Ln = Dy (7), Ho (8), and Er (9)) were also isostructural and formed 2D monolayer (2DM) frameworks with a P21/n space group. The structure variation from the 3D porous framework to the 2D double-decker to the 2D monolayer is attributed to the lanthanide contraction effect. Notably, six new coordination modes of 3,5-pyrazoled...

Shi-Ping Yan

Papers

Coordination Polymers Containing 1D Channels as Selective Luminescent Probes

Design and synthesis of 3d-4f metal-based zeolite-type materials with a 3D nanotubular structure encapsulated "water" pipe.

A nanotubular 3D coordination polymer based on a 3d-4f heterometallic assembly.

A Promising MgII‐Ion‐Selective Luminescent Probe: Structures and Properties of Dy–Mn Polymers with High Symmetry

Two- and three-dimensional lanthanide complexes: synthesis, crystal structures, and properties.