Synthesis And Hydrogen Releasing Properties Of Catalysts From Binary Nanopartcles Supported On Aluminum-based MOFs

Metal–organic frameworks?MOFs?have been emerging as a class of promising porous functional materials owing to their high porosity,large surface area,chemical tunability.Based upon the self-assembly of metalions with bridging ligands,MOFs often show fascinating extended network structures.Therefore,loading metal and non-metal nanoparticles?NPs?into the pores or on the surfaces of MOFs is expected to control the limited growth of NPs in the confined cavities,and produce well dispersed NPs,which could further increase their catalytic activities.On the other hand,ammonia borane?NH₃BH₃,AB?was considered as one of the leading candidates for hydrogen application owing to its high hydrogen content?19.6 wt%?,low molecular weight,non-toxicity,and stable in neutral aqueous solution.So far,different metal NPs immobilized on MOFs catalysts was synthesized by various methods and exhibits highly catalytic activity toward hydrolysis of ammonia borane at ambient temperature.Herein,Al-MOFs were used as the carrier of metal and non-metal NPs,and a series of stable and efficient catalysts were prepared by liquid impregnation and in situ reduction methods.Meanwhile,the synthesis,characterization and catalytic performance of as-synthesized catalysts were studied in detail.The following three aspects were mainly included:1.Bimetallic RuCo NPs were successfully deposited on the highly porous and hydrothermally stable nanofibrous metal-organic framework MIL-96?Al?by using a simple liquid impregnation strategy,and the powder XRD,FT-IR,BET,TEM,EDX,ICP-AES and XPS were employed to characterize the structure,size,composition and loading metal electronic states of the RuCo@MIL-96 catalysts.The catalytic property of RuCo@MIL-96 for hydrogen generation from the hydrolysis of ammonia borane at room temperature was investigated.The results show that Ru₁Co₁@MIL-96 exhibits much enhanced catalytic activity compared with monometallic Ru,Co counterparts loadings and RuCo NPs due to the uniform distribution of metal NPs and synergetic effect between Ru and Co particles as well as bifunctional effects between RuCo NPs and the host of MIL-96.The turn over frequency?TOF?value of the Ru₁Co₁@MIL-96catalyst is determined to be 320.7 mol H₂·min^-1?mol Ru?^-1,which is higher than most of the reported TOF values for the same reaction,and the activation energy?Ea?is36.00 kJ·mol^-1.Moreover,this catalyst exhibits satisfied durability after five cycles for the hydrolytic dehydrogenation of ammonia borane.2.Mono-metal Ru,Co,Ni and highly dispersed bimetallic RuCo,RuNi alloy nanoparticles with different molar ratio supported on MIL-110?Al?have been successfully synthesized by a simple liquid impregnation-reduction method.And XRD,TEM,EDX,ICP-AES,XPS,BET and FTIR were employed to characterize the above catalysts.Their catalytic activities were tested in the hydrogen generation from aqueous solution of ammonia borane at room temperature.The results show that the as-synthesized Ru₁Co₁@MIL-110 and Ru₁Ni₁@MIL-110 catalysts exhibit the highest catalytic activity,with a total TOF values of 584.7 and 377.2 mol H₂·min^-1?mol Ru?^-1,and the activation energy were determined to be 31.70 and 36.00 kJ·mol^-1.The excellent catalytic activity have been successfully achieved thanks to the strong bimetallic synergistic effects from RuCo,RuNi nanoparticals of the composites,uniform distribution of nanoparticles as well as bifunctional effects between RuCo,RuNi alloy nanoparticles and the host of MIL-110.In particular,the catalysts show satisfying durable stability after five cycles for the hydrolytic dehydrogenation of ammonia borane,which maintaining the initial catalytic activity of 79%and 76%.3.Metal Ru and non-metal P has been first immobilized on MIL-110?Al?,it was found that phosphorus deposited on the surface of MIL-110?Al?with Ru when sodium hypophosphite?NaH₂PO₂·H₂O?was used as reducing agent by optimization of synthetic conditions such as pH in the synthetic solution and temperature.The deposition of phosphorus should be effective on the size reduction and markedly reduces Ru nanoparticle size,and raise electrochemical active surface area of catalyst and improve the catalytic performance.TEM images show RuP nanoparticles are highly dispersed on the MIL-110?Al?surface.Their catalytic activities were tested in the hydrogen generation from aqueous solution of ammonia borane at room temperature.The results show that the as-synthesized RuP@MIL-110?Al?catalyst exhibits the highest catalytic activity,with a total turn over frequency value of 8646mL·H₂·min^-1?g catalyst?^-1,and the activation energy is determined to be 50.1 kJ·mol^-1.Moreover,the morphology and catalytic activity of RuP@MIL-110 did not change significantly after repeated use,showing excellent stability.