Design And Catalytic Performance Of Keggin-type Molybdosilicate Inorganic-organic Hybrid Crystalline Materials

Polyoxometalates(POMs),as a large class of metal-oxygen clusters,have attracted great attention in the fields of catalysis,medicine,and photochemistry due to their structural diversity.Researchers have considered several strategies to modify polyoxometallates,and a promising approach is to combine polyoxometallates with organic complexes and transition metals to form POM-based inorganic-organic hybrid complexes.In this way,while maintaining their structural integrity and inherent properties,this method also changes their dissolution characteristics,which is very beneficial for expanding the application of POM-based materials in electrochemically modified electrodes and heterogeneous catalysis.Therefore,this paper studies the synthesis and photocatalytic properties of inorganic-organic hybrid complexes based on Keggin-type polyoxometalates.The main contents and conclusions are as follows:1.Under the conditions of hydrothermal and using a small glass bottle,by introducing organic ligand 2,2’-bipyridyl and transition metal Cu ions,the transformation from Waugh-type polyoxometalates[MnMo9O32]6-to Keggin-type[SiMo12O40]4-,and successfully synthesized complex 1,whose molecular formula is(SiMo12O40)[Cu(2,2’bipy)2]2·2H2O.At the same time,the performance of complex 1 photocatalytic methylene blue and electrocatalytic nitrite was studied.The results showed that the degradation rate of methylene blue was close to 100%within 36 minutes,and there was no obvious attenuation after 4 cycles;In aqueous solution,the electroreduction of NaNO2 exhibits an electrocatalytic efficiency of 102.3%.2.Complex 2[(SiMo12O40)Cu6(2,2’-bipy)6(Mo6O22)]was prepared by introducing transition metal Cu2+and organic ligand 2,2’-bipyridine into the precursor Wangh-type polyoxometalates[MnMo9O32]6-,which not only completes the transformation of the polyoxometalates configuration,but also contains the isopolymolybdate structure,and the cationic part is through the Cu-N coordination bond,composed of six[Cu(2,2’bipy)]2+unit modified[Mo6O22]8-polyanion obtained.At the same time,the photocatalytic performance of methylene blue was studied,and it was found that MB aqueous solution could degrade 97.6%in only 24 minutes,and the photocatalytic mechanism was studied.Meanwhile,it showed an efficiency of 161.1%in the electrocatalytic reduction of nitrite.3.By changing the organic ligands,a new inorganic-organic complex 3 was synthesized by selecting 18-Crown-6 and Keggin-type[SiMo12O40]4-under a one-pot synthesis method:[H4SiMo12O40][LiCl([18]-Crown-6)(CH3CN)]2[HCl([18]-Crown-6)]2.The effect of different organic ligands on the performance of electrocatalytic reduction of nitrite was studied,and it showed a high electrocatalytic efficiency of 182.5%for NaNO2 at a nitrite content of 10 mM.At the same time,the electrocatalytic hydrogen evolution performance was studied,and the results showed that in 0.5 M H2SO4 solution,the overpotential at a current density of 10mA cm-2 was 117 mV,and the Tafel slope was 255 mV Dec-1,indicating a good electrocatalytic hydrogen evolution performance and stability.