Abstract:The SPR effect of monodisperse Ag nanoparticles in Ag@Ag3VO4/ZnCr LDH heterostructures exhibits high photocatalytic activity towards evolution of O2 and oxidation of phenol.
“…The resulting compound was characterized by a variety of characterization means, and its catalytic performance was investigated for the so-called "Mukaiyama" epoxidation of olefins, in which molecular oxygen was used as the oxidant and isobutyraldehyde was used as the co-reagent. Previous literature studies suggested that a few Ag-complexes are moderately active homogeneous catalysts for these attractive O 2 -mediated hydrocarbon/olefin oxidation processes [19][20][21][22][23][24]. Our present work shows that the hybrid polycatenane compound shows much higher catalytic activity than the corresponded POM or Ag-trz complexes.…”
A simple and efficient approach was developed for synthesizing a metal-organic polycatenated compound composed of Ag-triazole complexes and phosphomolybdic acid (PMA) clusters. The hybrid compound, namely {[Ag2(trz)2] [Ag24(trz)18]}[PMo12O40]2 (1) (trz = 1,2,4-triazole), showed high catalytic activity, selectivity and recyclability for the epoxidation of olefins with molecular oxygen as the oxidant and isobutyraldehyde as the co-reagent, and could even work well under ambient conditions. The special polycatenane framework, formed by interlocking [Ag24(trz)18]6+ nanocages, provides suitable space for filling the PMA clusters. The existence of multi-interactions, including π-π stacking, Ag-Ag interactions, and electrostatic interactions, should play a determinative role in fabricating the catalytically active and stable PMA-based polycatenane catalyst for aerobic epoxidation of olefins.
“…The resulting compound was characterized by a variety of characterization means, and its catalytic performance was investigated for the so-called "Mukaiyama" epoxidation of olefins, in which molecular oxygen was used as the oxidant and isobutyraldehyde was used as the co-reagent. Previous literature studies suggested that a few Ag-complexes are moderately active homogeneous catalysts for these attractive O 2 -mediated hydrocarbon/olefin oxidation processes [19][20][21][22][23][24]. Our present work shows that the hybrid polycatenane compound shows much higher catalytic activity than the corresponded POM or Ag-trz complexes.…”
A simple and efficient approach was developed for synthesizing a metal-organic polycatenated compound composed of Ag-triazole complexes and phosphomolybdic acid (PMA) clusters. The hybrid compound, namely {[Ag2(trz)2] [Ag24(trz)18]}[PMo12O40]2 (1) (trz = 1,2,4-triazole), showed high catalytic activity, selectivity and recyclability for the epoxidation of olefins with molecular oxygen as the oxidant and isobutyraldehyde as the co-reagent, and could even work well under ambient conditions. The special polycatenane framework, formed by interlocking [Ag24(trz)18]6+ nanocages, provides suitable space for filling the PMA clusters. The existence of multi-interactions, including π-π stacking, Ag-Ag interactions, and electrostatic interactions, should play a determinative role in fabricating the catalytically active and stable PMA-based polycatenane catalyst for aerobic epoxidation of olefins.
“…Such changes in the binding energies are generated because the electron density of NH 2 -MIL-125(Ti) decreases and that of ZnCr-LDH NSs increases. These findings clearly indicate that there exists an effective electronic coupling between the two components because of the hybridization, leading to not only the harvest of more incident photons to produce more photo-generated electrons and holes but also the suppression of the recombination of photo-generated electron and hole pairs due to an effective electron transfer between NH 2 -MIL-125(Ti) and ZnCr-LDH NSs 38,39 .Figure 7XPS spectra of (bottom in a , b , e ) pristine NH 2 -MIL-125(Ti), (bottom in c , d ) pristine ZnCr-LDH and (top in a – e ) the ML200 hybrid composite: ( a ) the full-spectrum survey, ( b ) Ti 2p, ( c ) Zn 2p, ( d ) Cr 2p and ( e ) O 1 s.…”
Novel hybrid composites of NH
2
-MIL-125(Ti) and ZnCr-layered double hydroxide nanosheets (ZnCr-LDH NSs) are developed for use as visible-light-active photocatalysts for hydrogen production based on water photolysis. The hybrid composites are obtained by growing NH
2
-MIL-125(Ti) in the presence of exfoliated ZnCr-LDH NSs using a solvothermal reaction. Hybridization of NH
2
-MIL-125(Ti) with exfoliated ZnCr-LDH NSs leads to significant effects on the morphology and optical properties of NH
2
-MIL-125(Ti). To find the optimum photocatalytic activity for hydrogen production by the hybrid composite photocatalysts, the content of ZnCr-LDH in this work is controlled. Compared to that of pristine NH
2
-MIL-125(Ti) and ZnCr-LDH, the hybrid composites exhibit an improved photocatalytic activity for hydrogen production under visible-light irradiation. In addition, the hybrid composite photocatalyst shows excellent photo-chemical stability. The improved photocatalytic activity is believed to benefit from the synergy of strong electronic coupling between NH
2
-MIL-125(Ti) and ZnCr-LDH NSs, expanded light absorption and band alignment to enhance the lifetime of photo-induced electrons and holes.
“…34 Recently, our group has reported Ag@Ag 3 VO 4 /ZnCr LDH heterostructure systems toward photocatalytic water oxidation and phenol degradation reaction. 35 However, no reports on the study of the heterostructure Ag@Ag 3 PO 4 /CNLDH nanocomposite as the photocatalyst and how the SPR electrons of Ag NPs together with Ag 3 PO 4 can participate in effective charge separation and protect the structural stability of exfoliated NiFe LDH nanosheets in this system have still been scarcely developed up to now.…”
In
this work, a series of heterostructure Ag@Ag
3
PO
4
/g-C
3
N
4
/NiFe layered double hydroxide
(LDH) nanocomposites were prepared by a combination of an electrostatic
self-assembly and in situ photoreduction method. In this method, positively
charged p-type Ag
3
PO
4
was electrostatically
bonded to the self-assembled negatively charged surface of the n–n-type
g-C
3
N
4
/NiFe (CNLDH) LDH hybrid material with
partial reduction of Ag
+
to metallic Ag nanoparticles (NPs)
by the photogenerated electrons and available surface −OH groups
of LDH under visible light irradiation. The presence of Ag
3
PO
4
as a p-type semiconductor, the surface plasmon resonance
(SPR) effect of metallic Ag NPs, and oxygen vacancies as O
v
-type defects in NiFe LDH could greatly achieve the quasi-type-II
p–n/n–n dual heterojunctions, which was revealed by
the shifted conduction band and valence band potentials in Mott–Schottky
(M–S) analysis. Among all the optimized heterostructures, CNLDHAgP4
could achieve the highest photocatalytic Cr(VI) reduction rate of
97% and phenol oxidation rate of 90% in 2 h. The heterostructure CNLDHAgP4
photocatalyst possesses a unique morphology consisting of cubic phases
of both Ag NPs and Ag
3
PO
4
, which adhered to
the thin and curvy layers of the CNLDH hybrid for smooth electronic
and ionic charge transport. Furthermore, the intimate Schottky barriers
formed at the interface of quasi-type-II p–n/n–n dual
heterojunctions were verified by the photoluminescence, linear sweep
voltammetry, M–S, electrochemical impedance study, high-resolution
transmission electron microscopy, and X-ray photoelectron spectroscopy
studies. The SPR effect of Ag NPs and oxygen vacancies as O
v
-type defect in NiFe LDH can effectively accelerate the threshold
of charge separation and be the main reason for the enhanced activity
achieved by the as-fabricated heterostructure photocatalyst.
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