Triazole-directed fabrication of polyoxovanadate-based metal–organic frameworks as efficient multifunctional heterogeneous catalysts for the Knoevenagel condensation and oxidation of alcohols

Abstract

By introducing 4-amino-1,2,4-triazole (4-NH2-trz), three new polyoxovanadate-based metal-organic frameworks (PMOFs) [Ni3(4-NH2-trz)6][V6O18]•3H2O (1), [Co3(4-NH2-trz)6][V6O18]•3H2O (2) and [Cu3OH(4-NH2-trz)3H2O][VO3]5•H2O (3) have been synthesized and thoroughly characterized by single-crystal X-ray diffraction (SXRD), powder X-ray...

New phosphotetradecavanadate hybrids: crystal structure, DFT analysis, stability and binding interactions with bio-macromolecules

“…In 1, the P-O distances vary from 1.532(4) to 1.543(4) Å and the angles are between 108.1(2)°and 110.7(2)°(Tables S2 and S3, ESI †), indicating normal tetrahedral phosphorus, while in 2 the central PO 4 tetrahedron has a type of disorder, with half-occupancy of the O-atom sites, akin to that noted in some Keggin-type [XM 12 O 40 ] n− heteropolyanions, indicated by Evans and Pope as being the result of a crystallographic disorder. 54 The P-O distances vary from 1.479 (11) to 1.566 (10) Å and the angles are between 105.9(6) and 113.0 (6) (Tables S4 and S5, ESI †), corresponding to distorted phosphorus tetrahedra.…”

“…Polyoxidometalates (POMs) are transition metal oxides where metal atoms usually present their highest oxidation states (usually group 5 or 6 in the periodic table, such as V V , Nb V , Ta V , Mo VI and W VI ) by binding to oxygen atoms, forming clusters with well-defined structures with the metal ions and their nearest coordination spheres acting as polyhedral building blocks. 1,2 POMs 3 have attracted increasing attention due to their potential applications in catalysis, [4][5][6][7][8][9][10][11] electrochemical energy storage and conversion [12][13][14] and magnetism, 15,16 as well as in several areas of material, medicinal and environmental sciences. [17][18][19][20][21][22][23][24][25] The size, structure and modifiable load densities of POMs often yield unexpected and interesting behaviours, allowing them to display different physical and chemical properties compared to traditional metal oxides.…”

“…48 POVs may be considered good candidates to produce both class I and class II type materials. 11,49,50 In this work, we selected bicapped Keggin phosphotetradecavanadate (PV 14 = methenamine = HMTA. Additionally, Hirshfeld surface analysis of these POVs was performed to analyse and study the nature of contacts in the crystal packing and DFT studies were performed to evaluate the relative stability of the H n PV14 species and their propensity to reduction and interaction with other molecules.…”

Successive constructions of regular tetra-, hexa- and octanuclear microporous polyoxovanadates(iii) for gas adsorption

“…Thus, substitutions of partial or all bridging oxygen atoms and bridging hydroxy groups on POV skeletons with pyrazole and triazole ligands are feasible ways to achieve POV building units and the self-assembly of POMOFs. [21][22][23][24][25] Moreover, MOFs possess extraordinary tunability of the pore geometry and surface function that can facilitate control over adsorptive separations of small gas molecules. 26,27 The Lewis basic amino groups in NH 2 -functionalized MOFs can generate stronger electrostatic interactions with acidic gas molecules such as CO 2 to enhance the selective gas adsorption capacity.…”

“…Thus, substitutions of partial or all bridging oxygen atoms and bridging hydroxy groups on POV skeletons with pyrazole and triazole ligands are feasible ways to achieve POV building units and the self-assembly of POMOFs. 21–25…”