Encapsulation of the vanadium substituted Keggin polyoxometalates [α-PVWO] and [α-PVWO] in HKUST-1

Two POM@MOF hybrid materials composed of a copper-based metal-organic framework (MOF) [Cu 3 (C 9 H 3 O 6 ) 2 (H 2 O) 3 ] n (HKUST-1) encapsulating vanadium-substituted Keggin polyoxometalates (POM), [α-PVW 11 O 40 ] 4− ( PVW 11 ) and [α-PV 2 W 10 O 40 ] 5− ( PV 2 W 10 ), were prepared and characterized. PVW 11 @HKUST-1 and PV 2 W 10 @HKUST-1 were synthesized hydrothermally by self-assembly of HKUST-1 in the presence of the preformed POMs, [α-PVW 11 O 40 ] 4− and [α-PV 2 W 10 O 40 ] 5− , respectively. The two POM@MOF composites were characterized by X-ray diffraction, TGA, BET surface area analysis and FT-IR and Raman spectroscopy. The electronic structure of the POM@MOF materials and their respective constituents is surveyed using solid state UV-vis reflectance spectroscopy. The UV-vis spectra order the oxidizing strength of the POM constituents ([α-PV 2 W 10 O 40 ] 5− > [α-PVW 11 O 40 ] 4− ) and reveal the distinct electronic structure of the POM@MOF materials obtained by synthetic encapsulation of mono- and di-vanadium substituted Keggin polyoxotungstates in HKUST-1. Solid state UV-vis reflectance spectra reveal the distinct electronic structure of POM@MOF materials obtained by synthetic encapsulation of mono- and di-vanadium substituted Keggin polyoxotungstates in HKUST-1.