Porous coordination polymers with ubiquitous and biocompatible metals and a neutral bridging ligand.

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.

High CO2 /CH4 Selectivity of a Flexible Copper(II) Porous Coordination Polymer under Humid Conditions.

Invited for this month's cover is the group of Prof. Shin-ichiro Noro from Hokkaido University, Japan. The cover picture shows a copper(II) porous coordination polymer that can adsorb CO2 over CH4 at high selectivity under CO2 /CH4 mixed gas conditions, even with the coexistence of water. Read the full text of the article at 10.1002/cplu.201500278.

High CO2 /CH4 Selectivity of a Flexible Copper(II) Porous Coordination Polymer under Humid Conditions.

The development of highly efficient CO2 separation materials is very important for environmental preservation and energy conservation. Crystalline porous coordination polymers (PCPs)/metal-organic frameworks are one of a number of promising types of porous materials for CO2 separation because of their controllable pore size, shape and surface function. Simultaneously, the unique structural flexibility of PCPs affords both high CO2 selectivity and inexpensive regeneration. However, this family of materials suffers from the coexistence of water that destroys the framework of PCPs and its adsorption in the pores is greater than that of CO2 , which results in a deterioration in CO2 -separation performance. Herein, a flexible and hydrophobic CuII PCP that is stable towards water has been designed and synthesised. This PCP has extremely high adsorption selectivity for CO2 over CH4 , derived from its structural flexibility. Furthermore, the obtained water-tolerant flexible PCP, under CO2 /CH4 mixed-gas conditions, exhibits highly selective CO2 adsorption over CH4 , even in the presence of water.

Structural optimization of interpenetrated pillared-layer coordination polymers for ethylene/ethane separation.

With the goal of achieving effective ethylene/ethane separation, we evaluated the gas sorption properties of four pillared-layer-type porous coordination polymers with double interpenetration, [Zn2(tp)2(bpy)]n (1), [Zn2(fm)2(bpe)]n (2), [Zn2(fm)2(bpa)]n (3), and [Zn2(fm)2(bpy)]n (4) (tp = terephthalate, bpy = 4,4'-bipyridyl, fm = fumarate, bpe = 1,2-di(4-pyridyl)ethylene and bpa = 1,2-di(4-pyridyl)ethane). It was found that 4, which contains the narrowest pores of all of these compounds, exhibited ethylene-selective sorption profiles. The ethylene selectivity of 4 was estimated to be 4.6 at 298 K based on breakthrough experiments using ethylene/ethane gas mixtures. In addition, 4 exhibited a good regeneration ability compared with a conventional porous material.

Dense coordination network capable of selective CO2 capture from C1 and C2 hydrocarbons.

We elucidated the specific adsorption property of CO(2) for a densely interpenetrated coordination polymer which was a nonporous structure and observed gas separation properties of CO(2) over CH(4), C(2)H(4), and C(2)H(6), studied under both equilibrium and kinetic conditions of gases at ambient temperature and pressure.

Modification of flexible part in Cu(2+) interdigitated framework for CH(4)/CO(2) separation.

The structural flexibility of Cu(2+) interdigitated layer type framework was controlled and the compound represented clear separation property of CH(4)/CO(2) at range of 0-1.0 MPa and recovery of adsorbed CO(2) above 0.1 MPa.