Control of the physical and chemical properties of porous materials has been an ongoing challenge for the optimization of functions, such as gas storage, separation, and catalysis. For example, a high surface area is important for large-volume gas uptake, and the control of pore shape is also significant for molecular separation.[1] These requirements are also valid for porous coordination polymers (PCPs) or metal-organic frameworks (MOFs), which consist of metal ions and organic linkers.[2] This class of adsorbent has received attention because of its structural versatility and physical properties, such as magnetism and redox activity.[3] Among the PCP compounds, flexible frameworks have been identified as a unique type of porous material because of their guestresponsive transformations.[4] This structural transformation is often directly related to the functionality of these frameworks; gas recognition separation or slow drug release are good examples in this respect. [5] The flexibility of the network must be modulated to precisely control these functions and to tailor the network performance, and much effort has been expended in creating flexible compounds.[6] However, there have been few reports on the rational incorporation of flexibility in the known PCP compounds as their synthesis is difficult.[7] Herein, we describe the preparation of ligand-based solid solutions of flexible PCPs and our attempts to overcome difficulties in the precise flexibility control and resulting gas sorption properties. A few approaches toward ligand-based solid solutions of robust metal-organic framework have been reported, [8] although corresponding structural information and control of their adsorptive functions has not been observed. We have synthesized two distinct interdigitated frameworks that contain different organic ligands, and have created a series of solid solutions based on these frameworks. These compounds exhibited a range of flexible adsorption properties, and their bimodal properties enabled them to show an improved performance compared with the two pure compounds CID-5 and CID-6 in the separation of a CO 2 /CH 4 mixture.The two flexible compounds with an interdigitation motif of 2D layers, [{Zn(5-NO 2 -ip)(bpy)}(0.5DMF·0.5MeOH)] n (CID-5'G; 5-NO 2 -ip = 5-nitroisophthalate, bpy = 4,4'-bipyridyl, and CID = coordination polymer with an interdigitated structure), and [{Zn(5-MeO-ip)(bpy)}(0.5 DMF·0.5 MeOH)] n (CID-6'G; 5-MeO-ip = 5-methoxyisophthalate), were prepared from Zn(NO 3 ) 2 ·6 H 2 O and either of the ligands in a 1:1 v/v DMF/MeOH mixture. The crystal structures are shown in Figure 1. For both compounds, two carboxylate groups coordinate to Zn 2+ ions to form eight-membered rings, and the bpy groups coordinate to the axial position of the Zn 2+ ions to create the 2D layered structure. The layers are assembled in an interdigitated fashion with micropores formed within the structure. Both frameworks can be

A new porous coordination polymer, ([La(BTB)H 2 O] · solvent ( 1 ⊃ ⊃ guest)), is synthesized. Gas adsorption, ideal adsorbed solution theory (IAST) and breakthrough experiments of it exhibits high CH 4 separation capability toward CO 2 and C2 hydrocarbons at 273 K. In addition, this also shows good water and chemical stability, in particular, it is stable at pH = 14 at 100 ° C, which is unprecedented for carboxylate-based porous coordination polymers. Furthermore, the effective adsorption site for separation is revealed by using an in situ diffuse refl ectance IR fourier transform (DRIFT) spectra study.

5Gas separation properties of CH 4 /CO 2 and CH 4 /C 2 H 6 for flexible 2D porous coordination polymers under equilibrium gas condition and mixture gas flowing condition were investigated and the gas separation efficiencies were optimized by precise tuning of flexibility in ligand-base solid solution compounds. Notes and references70

The design of inexpensive and less toxic porous coordination polymers (PCPs) that show selective adsorption or high adsorption capacity is a critical issue in research on applicable porous materials. Although use of Group II magnesium(II) and calcium(II) ions as building blocks could provide cheaper materials and lead to enhanced biocompatibility, examples of magnesium(II) and calcium(II) PCPs are extremely limited compared with commonly used transition metal ones, because neutral bridging ligands have not been available for magnesium(II) and calcium(II) ions. Here we report a rationally designed neutral and charge-polarized bridging ligand as a new partner for magnesium(II) and calcium(II) ions. The three-dimensional magnesium(II) and calcium(II) PCPs synthesized using such a neutral ligand are stable and show selective adsorption and separation of carbon dioxide over methane at ambient temperature. This synthetic approach allows the structural diversification of Group II magnesium(II) and calcium(II) PCPs.

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