The review is devoted to the analysis of the strategies used for the design and preparation of zeoliteencapsulated subnanometric metal clusters.Nowadays this topic is often considered as one of the most rapidly develo...The review is devoted to the analysis of the strategies used for the design and preparation of zeoliteencapsulated subnanometric metal clusters.Nowadays this topic is often considered as one of the most rapidly developing in heterogeneous catalysis.On the one hand,it is due to the great fundamental interest to the structure and properties of such materials and,on the other hand,it is related to their unique catalytic properties and great perspectives for their application in a number of important heterogeneous catalytic reactions aimed at the conversion of non-conventional feedstocks and building a low-carbon(decarbonized)economy.The application of metal-containing zeolites allows the challenges related to the development of novel tandem processes,which require simultaneous proceeding of several catalytic reactions over one catalyst,to be addressed.The coupling of zeolites and metals in a single catalyst allows for fine-tuning the properties of tandem catalysts both by engineering the nature,state and localization of the metal active sites,and by mastering the unique porous structure of the zeolites with active sites of different nature.The contribution presents the methodological aspects of the synthesis of the described systems,highlighting their advantages,limitations and problems related to their applications.In particular,both novel methods of metal encapsulation and conventional ones known for decades are analyzed and systematized.Special attention is paid to the conditions under which simple conventional methods allow the encapsulation of nanoclusters in zeolite.As a result,the recommendations on the most preferable approaches for obtaining specific zeolite–metal combinations are given and promising directions for the development of synthesis methods are highlighted.展开更多
Planar cobalt(Ⅱ)Schiff-base complexes show modified structural and functional properties after encapsulation inside zeolite-Y.In the free-state,the reactivity of the cobalt(Ⅱ)Schiff-base complexes is primarily contr...Planar cobalt(Ⅱ)Schiff-base complexes show modified structural and functional properties after encapsulation inside zeolite-Y.In the free-state,the reactivity of the cobalt(Ⅱ)Schiff-base complexes is primarily controlled by the electronic effects of the different substituent groups present in the complexes.However,the encapsulation of these complexes within the supercages of zeolite-Y causes the alteration of the electron density around the metal center and subsequently modifies the reactivity.We have intended to study two environment-friendly reactions,i.e.,degradation of rhodamine B dye and transformation of CO_(2) with catalysts containing relatively lower metal content like cobalt(Ⅱ)salophen complexes encapsulated in zeolite-Y.To comprehend these systems well,XRD analysis,SEM-EDX,FTIR,XPS,TGA,BET,and UV-visible spectroscopy and DFT studies have been performed.XRD and BET studies along with XPS,experimental and theoretical electronic spectroscopic studies clearly revealed successful encapsulation of the vip complex with some alteration of the electronic environment around the metal center.Catalytic studies identified that encapsulated complexes exhibit the better results for dye degradation.Zeolite-Y encapsulated 5-methoxy cobalt(Ⅱ)sal-1,2-phen(CoL5-Y)could degrade 89.6%of the dye while neat CoL5 could only degrade 30.2%.Comparative studies of structural and catalytic modifications allowed a rational explanation of enhanced reactivity of zeolite encapsulated metal complexes for the degradation of rhodamine B dye compared to their corresponding free-states.The catalysts showing the maximal and minimal activities for dye degradation in the series,i.e.,CoL1,CoL1-Y,CoL5,and CoL5-Y,have been tested for coupling of CO_(2) and styrene oxide.The TON for CO_(2) uptake using the heterogeneous catalyst CoL5-Y was found to be 2949,while using the homogeneous counterpart,it was only 339.展开更多
文摘The review is devoted to the analysis of the strategies used for the design and preparation of zeoliteencapsulated subnanometric metal clusters.Nowadays this topic is often considered as one of the most rapidly developing in heterogeneous catalysis.On the one hand,it is due to the great fundamental interest to the structure and properties of such materials and,on the other hand,it is related to their unique catalytic properties and great perspectives for their application in a number of important heterogeneous catalytic reactions aimed at the conversion of non-conventional feedstocks and building a low-carbon(decarbonized)economy.The application of metal-containing zeolites allows the challenges related to the development of novel tandem processes,which require simultaneous proceeding of several catalytic reactions over one catalyst,to be addressed.The coupling of zeolites and metals in a single catalyst allows for fine-tuning the properties of tandem catalysts both by engineering the nature,state and localization of the metal active sites,and by mastering the unique porous structure of the zeolites with active sites of different nature.The contribution presents the methodological aspects of the synthesis of the described systems,highlighting their advantages,limitations and problems related to their applications.In particular,both novel methods of metal encapsulation and conventional ones known for decades are analyzed and systematized.Special attention is paid to the conditions under which simple conventional methods allow the encapsulation of nanoclusters in zeolite.As a result,the recommendations on the most preferable approaches for obtaining specific zeolite–metal combinations are given and promising directions for the development of synthesis methods are highlighted.
基金the DST-FIST,Department of Chemistry,and Department of Physics,BITS Pilani,for the instrumental facilityhey also thank MNIT,Jaipur,for the XPS measurements.
文摘Planar cobalt(Ⅱ)Schiff-base complexes show modified structural and functional properties after encapsulation inside zeolite-Y.In the free-state,the reactivity of the cobalt(Ⅱ)Schiff-base complexes is primarily controlled by the electronic effects of the different substituent groups present in the complexes.However,the encapsulation of these complexes within the supercages of zeolite-Y causes the alteration of the electron density around the metal center and subsequently modifies the reactivity.We have intended to study two environment-friendly reactions,i.e.,degradation of rhodamine B dye and transformation of CO_(2) with catalysts containing relatively lower metal content like cobalt(Ⅱ)salophen complexes encapsulated in zeolite-Y.To comprehend these systems well,XRD analysis,SEM-EDX,FTIR,XPS,TGA,BET,and UV-visible spectroscopy and DFT studies have been performed.XRD and BET studies along with XPS,experimental and theoretical electronic spectroscopic studies clearly revealed successful encapsulation of the vip complex with some alteration of the electronic environment around the metal center.Catalytic studies identified that encapsulated complexes exhibit the better results for dye degradation.Zeolite-Y encapsulated 5-methoxy cobalt(Ⅱ)sal-1,2-phen(CoL5-Y)could degrade 89.6%of the dye while neat CoL5 could only degrade 30.2%.Comparative studies of structural and catalytic modifications allowed a rational explanation of enhanced reactivity of zeolite encapsulated metal complexes for the degradation of rhodamine B dye compared to their corresponding free-states.The catalysts showing the maximal and minimal activities for dye degradation in the series,i.e.,CoL1,CoL1-Y,CoL5,and CoL5-Y,have been tested for coupling of CO_(2) and styrene oxide.The TON for CO_(2) uptake using the heterogeneous catalyst CoL5-Y was found to be 2949,while using the homogeneous counterpart,it was only 339.
