A new 28-Ni-added poly(polyoxometalate) with B atoms: synthesis, structure and catalysis for Knoevenagel condensation

40Ni-Added Poly(polyoxometalate) Assembled by {Ni6GeW9} and {Ni8(GeW9)2} Units: Structure, Magnetic, and Heterogeneous Catalysis Properties

“…Polyoxometalates (POMs) are a well-known and unique class of higher-valent metal-oxo clusters, based mainly on V, Nb, Ta, Mo, and W. In particular, transition-metal added polyoxometalates (TMAPs) have been attracting tremendous attention in the research directions of catalysis, magnetism, and materials science due to diverse molecular structures and rich physicochemical properties. − Hence, it is of great importance for the further exploration of POM chemistry to prepare novel TMAPs. To date, several highly nuclear TMAPs have been reported, including Co 16 -, Fe 28 -, Fe 48 -, Cu 20 -, Zr 24 -, and Ni 25 -added POMs, but the synthesis of highly nuclear TMAPs is rather difficult and the family of high-nuclearity TMAPs is still very small.…”

“…Up to now, most of these reported TMAPs were synthesized by a conventional solution method. In contrast, our research team has been committed to the research of hydrothermal synthesis for many years, leading to the successful syntheses of various structurally new high-nuclearity TMAPs, including Ni 28 , Zr 24 , Co 25 , Ni 20 , Ni 22 , Ni 24 , and Ni 40 . However, taking a closer look at the synthetic details, most of the highly nuclear Ni-added POMs (NiAPs) have been prepared with the addition of organic amines. − Considering that organic amines can strongly coordinate to Ni 2+ ions, it could reduce the number of terminal aqua ligands in the catalytically active Ni centers, finally leading to decreased catalytic activities.…”

“…For instance, high-nuclearity Ni 20 -, Ni 22 -, Ni 24 -, and Ni 40 -added POMs have exhibited interesting molecular magnetism with overall ferromagnetic interactions. In addition, the NiAPs also showed broad catalytic applications, including Knoevenagel condensation, oxidation of sulfides, visible-light-driven water oxidation, photoreduction of CO 2 , visible-light-driven H 2 evolution, − etc. Given the fact that Ni centers are the active sites of natural [NiFe] hydrogenases for efficient hydrogen uptake and proton reduction, comprehensive studies of NiAPs as catalysts for photocatalytic H 2 production remain a particularly interesting research area.…”

Three Double-Layered {Ni8}@{Bn}2 (n = 3, 4, 6) Cluster Sandwiched Polyoxometalates

“…Polyoxometalates (POMs) are of metal-oxide clusters, possessing unrivaled structural diversity and demonstrating great potential in a wide range of fields, including catalysis, biomedicine, magnetism, and materials science. − Within the class of transition-metal added POMs (TMAPs), , sandwiched structures built by two lacunary POM fragments linked by a diverse and versatile TM-oxo clusters (TMOCs) are rather prominent. The research on sandwiched TMAPs can be traced back to 1973, when [Co 4 (H 2 O) 2 (PW 9 O 34 ) 2 ] 10– was made, followed by numerous reports on sandwiched TMAPs with various TMOCs, directly resulting in the largest sandwiched subclass. − However, the number of TM centers embedded in the sandwich belts is usually less than six, primarily because the vacant sites of lacunary POM units are saturatedly occupied by TM ions so as to hardly combine with more TM cations and in situ generated larger TMOCs in the sandwich belt become unstable without the assistance of extraneous structure-stabilizing agents such as phosphate, carbonate, or small organic ligands.…”

“…Polyoxometalates (POMs) are of metal-oxide clusters, possessing unrivaled structural diversity and demonstrating great potential in a wide range of fields, including catalysis, biomedicine, magnetism, and materials science. 1−14 Within the class of transition-metal added POMs (TMAPs), 15,16 sandwiched structures built by two lacunary POM fragments linked by a diverse and versatile TM-oxo clusters (TMOCs) are rather prominent. The research on sandwiched TMAPs can be traced back to 1973, 17 when [Co 4 (H 2 O) 2 (PW 9 O 34 ) 2 ] 10− was made, followed by numerous reports on sandwiched TMAPs with various TMOCs, directly resulting in the largest sandwiched subclass.…”