Phosphinic Acid Based Linkers: Building Blocks in Metal–Organic Framework Chemistry

Abstract

Metal-organic frameworks (MOFs) are achemically and topologically diverse family of materials composed of inorganic nodes and organic linkers bound together by coordination bonds.P resented here are two significant innovations in this field. The first is the use of an ew coordination group,p henylene-1,4-bis(methylphosphinic acid) (PBPA), ap hosphinic acid analogue of the commonly used terephtalic acid. Use of this new linker group leads to the formation of ah ydrothermally stable and permanently porous MOF structure.T he second innovation is the application of electron-diffraction tomography,coupled with dynamic refinement of the EDT data, to the elucidation of the structure of the new material, including the localization of hydrogen atoms.

Metal Phosphonates and Phosphinates

“…As mentioned above, carboxylic acids have usually been the linkers of choice in "traditional" MOF chemistry. A few examples of microporous compounds based on phosphonate monoesters (Figure 15), which share some features with phosphinic acid linkers, have been reported recently [81][82][83][84]. On the other hand, until very recently, no permanently porous metal phosphinate MOFs were reported.…”

“…On the other hand, until very recently, no permanently porous metal phosphinate MOFs were reported. In 2018, Hynek et al [82] used the linker phenylene-1,4-bis(methylphosphinic acid), hereafter denoted PBPA(Me), which can be seen as an analogue of terephthalic acid, the most common linker in MOF chemistry. Three different compounds were obtained by the reaction of PBPA(Me) with Fe(III) salts in different conditions (Figure 16): ICR-1 (ICR stands for Institute of Inorganic ChemistryŘež), prepared in water, has a non-porous 3D framework, which is isoreticular to a previously reported Zr phosphonate [85]; ICR-2, prepared in ethanol, is instead porous, with hexagonal channels with diameters of 0.8 nm running along the c-axis and a Brunauer-Emmett-Teller (BET) surface area of 731 m 2 •g −1 ; ICR-3, prepared in N,N -dimethylformamide is a layered dense phase.…”

A Semiconductive and Microporous One-Dimensional Tubular Metal-Organic Framework

“…Recently, two new families of MOFs have emerged, which employ phosphonic and phosphinic acids as metal-binding units, in contrast with the conventional MOFs that contain carboxylates and azolates. [25][26][27][28] Phosphonic acids are able to support extremely rich metal-binding modes, while phosphinic acids have carboxylate-like metal-binding modes. [28] The presence of d-orbitals in the phosphorus atom can give rise to rich electronic interactions, which have resulted in completely different geometries compared to those of conventional MOFs.…”

“…[25][26][27][28] Phosphonic acids are able to support extremely rich metal-binding modes, while phosphinic acids have carboxylate-like metal-binding modes. [28] The presence of d-orbitals in the phosphorus atom can give rise to rich electronic interactions, which have resulted in completely different geometries compared to those of conventional MOFs. [25][26][27][28] Owing to the higher strength of the C-P and P-O bonds compared to R-C=O bonds, phosphonate MOFs exhibit higher thermal and chemical stabilities compared to conventional MOFs.…”

“…[28] The presence of d-orbitals in the phosphorus atom can give rise to rich electronic interactions, which have resulted in completely different geometries compared to those of conventional MOFs. [25][26][27][28] Owing to the higher strength of the C-P and P-O bonds compared to R-C=O bonds, phosphonate MOFs exhibit higher thermal and chemical stabilities compared to conventional MOFs. [12,29,30] To the best of our knowledge, the total number of microporous phosphonate MOFs is currently less than 0.001% of the total number of reported MOFs.…”