Efficient production of fuels and chemicals from lignocellulosic biomass is the main goal of biorefinery processes. Herein, the metal-modified heteropolyacids with tunable Lewis and Brønsted acid sites were designed as the monolithic multifunctional catalyst for valorizing cellulose and lignocellulosic biomass to alkyl levulinate, a versatile platform molecule. Among them, Al-exchanged two protons of H 4 SiW 12 O 40 (Al 2/3 H 2 SiW 12 O 40 ) was found to be uniquely effective. The kinetic behavior describing the conversion of cellulose to ethyl levulinate was investigated to monitor the process, and compared between parent H 4 SiW 12 O 40 and Al 2/3 H 2 SiW 12 O 40 to understand the mechanistic role of Al 3+ . The introduction of Al 3+ substantially facilitated cellulose depolymerization and glucose-to-fructose isomerization , leading to a high rate and product selectivity. The estimated activation energies for cellulose degradation and glucopyraoside alcoholysis decreased by 50.6 kJ/mol and 40.9 kJ/mol, respectively. 50–72% yields of ethyl levulinate were accomplished from cellulosic biomasses such as pine wood, eucalyptus, bamboo, bagasse and Napier grass. Al 2/3 H 2 SiW 12 O 40 allowed cellulose conversion in various linear alcohols producing high-yield alkyl levulinate, and could be reused multiple times with a good stability. This study opens a reliable and promising avenue for one-pot transformation of cellulose and raw lignocellulosic biomass to ester compounds.
InP quantum dots (QDs) show a unique promise for display and lighting applications. However, the synthesis of InP QDs with high optical quality is much more difficult compared to that of Cd-based QDs and Pb-based perovskites. Here, we established a layer-by-layer modification approach to improve the optical properties of the InP QDs. InP QDs with green emission were prepared using tris(dimethylamino)phosphine ((DMA)3P). By introducing aluminum isopropoxide (AIP) twice during the formation of the ZnSeS and ZnS shell layers, we increased the photoluminescence quantum yield (PLQY) of the resulting Al-modified InP/ZnSeS/ZnS QDs to 96%. The full-width-at-half-maximum (fwhm) could be narrowed to 37 nm. It was speculated that the introduction of Al could alleviate the charge mismatch between the cores and shells and passivate surface defects. In addition, AIP might form oxides on the outer layers of QDs, thus enhancing their stability. Moreover, the green light-emitting diode (LED) based on Al-modified InP/ZnSeS/ZnS QDs performed well with a maximum power efficiency of 28 lm/W. This work finds a way to obtain InP QDs of high brightness and narrow emission by modification in the midsynthetic process, which will inspire the synthesis of better InP QDs.
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