Advances and Challenges in the Creation of Porous Metal Phosphonates

Abstract

In the expansive world of porous hybrid materials, a category of materials that has been rather less explored than others and is gaining attention in development is the porous metal phosphonates. They offer promising features towards applications which demand control over the inorganic–organic network and interface, which is critical for adsorption, catalysis and functional devices and technology. The need to establish a rationale for new synthesis approaches to make these materials in a controlled manner is by itself an important motivation for material chemists. In this review, we highlight the various synthetic strategies exploited, discussing various metal phosphonate systems and how they influence the properties of porous metal phosphonates. We discuss porous metal phosphonate systems based on transition metals with an emphasis on addressing challenges with tetravalent metals. Finally, this review provides a brief description of some key areas of application that are ideally suited for porous metal phosphonates.

Two Cu-Based Phosphonate Metal–Organic Frameworks as Efficient Water-Splitting Photocatalysts

“…Although scarcely explored when compared with other metal–organic frameworks (MOFs; phosphonate-MOFs vs carboxylate-MOFs ≈1:10; according to Web of Science, May 2023), phosphonate-based MOFs (P-MOFs) present an extremely high scientific interest associated with (i) the versatility of metal bonding modes in the structure of P-MOFs caused by the multiple protonation states of the R–PO 3 H 2 groups; (ii) their capability to form stronger bonds with soft cations (e.g., divalent) compared to carboxylates due to their lower hard character (following the hard–soft acid–base theory), leading to chemically robust MOFs, , and (iii) the formation of numerous non-covalent interactions (e.g., hydrogen bonds) inside their structures, resulting in the formation of P-MOFs with a high structural richness . However, P-MOFs are difficult to synthesize and to be obtained as large crystals, hindering the determination of their crystal structure by conventional techniques.…”

Microporous Metal‐Phosphonates with a Novel Orthogonalized Linker and Complementary Guests: Insights for Trivalent Metal Complexes from Divalent Metal Complexes

“…[21,22] Alternatively, phosphonate linkers have received significant interest due to their ability to strongly bind metal ions resulting in thermally and chemically resistant MOF structures. [23][24][25][26][27][28] Similar to the sulfonate functional group, phosphonates exhibit an abundance of coordination modes and additionally, have varying degrees of protonation. [29][30][31] The double edge of the structural pliancy is that metal-phosphonates often pack to form nonporous layered structures with minimal porosity.…”

“…Alternatively, phosphonate linkers have received significant interest due to their ability to strongly bind metal ions resulting in thermally and chemically resistant MOF structures [23–28] . Similar to the sulfonate functional group, phosphonates exhibit an abundance of coordination modes and additionally, have varying degrees of protonation [29–31] .…”

High Proton Conductivity of a Bismuth Phosphonate Metal–Organic Framework with Unusual Topology

“…Nevertheless, P-MOFs are attracting a growing interest since phosphonate ligands can lead to robust MOFs with high versatility in the coordination modes (i.e., different protonation states) and multiple noncovalent interactions. 24,25 Furthermore, P-MOFs have recently emerged as excellent proton conductive materials with the potential for proton exchange membranes (PEMs), which are currently used in PEM fuel cells (PEMFCs) 26−28 and electrolyzers. 29−31 These devices are of great relevance considering the growing environmental issues associated with the emission of greenhouse gases caused by conventional fuels.…”