The burgeoning field of metal − organic frameworks or porous coordination polymers has received increasing interest in recent years. In the last decade these microporous materials have found several applications including storage and separation of gases, sensors, catalysis and functional materials. In order to better design new metal − organic frameworks and porous coordination polymers with specific functionalities a fundamental issue is to achieve a basic understanding of the relationship between molecular parameters and structures, preferred adsorption sites and properties by using using modern theoretical methods. The focus of this mini-review is a description of the potential and emerging applications of metal − organic frameworks.

The amino-tagged bis(pyrazolate) MOF Zn(BPZNH2) is an excellent CO2 adsorbent and CO2 epoxidation catalyst under green conditions.

The metal-organic frameworks (MOFs) M(BPZNO ) (M=Co, Cu, Zn; H BPZNO =3-nitro-4,4'-bipyrazole) were prepared through solvothermal routes and were fully investigated in the solid state. They showed good thermal stability both under a N atmosphere and in air, with decomposition temperatures peaking up to 663 K for Zn(BPZNO ). Their crystal structure is characterized by 3D networks with square (M=Co, Zn) or rhombic (M=Cu) channels decorated by polar NO groups. As revealed by N adsorption at 77 K, they are micro-mesoporous materials with BET specific surface areas ranging from 400 to 900 m g . Remarkably, under the mild conditions of 298 K and 1.2 bar, Zn(BPZNO ) adsorbs 21.8 wt % CO (4.95 mmol g ). It shows a Henry CO /N selectivity of 15 and an ideal adsorbed solution theory (IAST) selectivity of 12 at p=1 bar. As a CO adsorbent, this compound is the best-performing MOF to date among those bearing a nitro group as a unique chemical tag. High-resolution powder X-ray diffraction at 298 K and different CO loadings revealed, for the first time in a NO -functionalized MOF, the insurgence of primary host-guest interactions involving the C(3)-NO moiety of the framework and the oxygen atoms of carbon dioxide, as confirmed by Grand Canonical Monte Carlo simulations. This interaction mode is markedly different from that observed in NH -functionalized MOFs, for which the carbon atom of CO is involved.

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The novel coordination polymers M(Me 2 BPZ) (M = Co, Zn; H 2 Me 2 BPZ = 3,3′-dimethyl-1H,1′H-4,4′-bipyrazole), M(H 2 Me 2 BPZ)(CH 3 COO) 2 -(H 2 O) 2 (M = Co, Ni), and Cu(H 2 Me 2 BPZ)(Cl) 2 were isolated along conventional or solvothermal routes. Their crystal structure was unveiled by powder X-ray diffraction (PXRD), while their thermal stability was assessed by coupling thermogravimetric analysis to variable-temperature PXRD. The textural properties of the M(Me 2 BPZ) (M = Co, Zn) compounds, featuring three-dimensional open frameworks with one-dimensional channels, were assessed by N 2 and CO 2 adsorption at 77 and 273 K, respectively, and compared to those of the nonmethylated isostructural counterparts M(BPZ) (M = Co, Zn; H 2 BPZ = 1H,1′H-4,4′-bipyrazole). The positive effect of the methyl groups in CO 2 adsorption, suggested by the adsorption energy trend [E ads (M(Me 2 BPZ)) > E ads (M(BPZ))] and substantiated by theoretical calculations at the B3LYP-D3 level coupled to topological analyses, is counterbalanced by the higher steric hindrance of Me 2 BPZ 2− vs BPZ 2− , finally reducing the amount of gas adsorbed by the M(Me 2 BPZ) couple vs the M(BPZ) one.