Functionalization,Characterization And Catalytic/Adsorptive Applications Of Stable Zirconium-based Porous Materials

In recent years,stricter environmental regulations in China and elsewhere have forced the scientific community to find alternatives to the conventional catalysts and adsorbents.Therefore,development and fabrication of stable,economically viable and environmentally benign functional porous materials with large surface area,have recently received much attention.Zirconium-based porous materials due to their thermochemical stability,environmentally benign stature and economic viability,have the potential to meet the modern-day challenges.In this work,we developed different strategies for synthesis and modification of Zr-based porous materials for heterogeneous catalytic and adsorptive applications.The effect of heteropoly acid or noble-metal(in this case Pd)on the physico-chemical traits of the host material were explored.The original innovative works are summarized as:(1)Development of novel hybrid catalyst HPW@Zr(BTC),composed of phosphotungstic acid(HPW)and Zr-MOF,via one-pot direct solvothermal synthesis method.High HPW loading(up to 32.3 wt.%)was achieved.Characterization of the composite catalyst proved that the crystalline morphology and thermostability of Zr(BTC)was enhanced by HPW up to a threshold wt.%loading.The catalytic activity of the hybrid composite was explored via Friedel-Crafts acylation of anisole with benzoyl chloride.The 28.2 wt.%HPW@Zr(BTC)showed excellent catalytic performance,with 99.4%anisole conversion and 97.9%yield(p-methoxybenzophenone)under solvent free conditions.Excellent retention of catalytic activity was achieved after at least five consecutive runs due to non-observable HPW leaching.The promising activity and stability of the catalyst forecasted its potential industrial applications.(2)The work describes synthesis of Pd-impregnated Zr-MOF,as heterogeneous catalysts for Suzuki-Miyaura cross-coupling reactions.Different co-modulated synthesis strategy was used to synthesize stable large MOF crystals.The catalysts showed excellent catalytic activity in H2O:EtOH solvent,achieving 97.2%yield of biphenyl,with cross-coupling of phenyl bromide and benzoboronic acid at relatively mild reaction conditions.The best performance was achieved by Pd@Zr(BTC)catalyst,prepared by a one-pot solvothermal method.The catalyst was reusable for multiple runs maintaining its efficiency(3)The work reports on the adsorptive removal of benzothiophene from liquid fuel using a highly porous metal-organic framework based on a bicomponent zirconium benzene-tricarboxylate,and its post-synthetically modified hybrid form with dodeca-tungstophosphoric acid(HPW/Zr(BTC).Temperature and concentration dependent BT adsorption data were in good agreement with the non-linear Langmuir model combined with van't Hoff description of the heat of adsorption.The maximum predicted adsorption capacities were estimated to be 290 and 238 mg.g-1 for HPW(1.5)/Zr(BTC)and Zr(BTC)comparable to the contemporary reported adsorbents.Although the highly porous Zr(BTC)had good adsorptive sites,its adsorption capacity was further enhanced by incorporation of HPW.This was attributed to the synergistic effect of active acid sites provided by HPW and the open metal-sites on the Zr(BTC)framework.(4)A novel bifunctional catalyst,consisting of palladium metal and molybdovanadophosphoric acid(PMV)supported on mesoporous zirconia,was developed for catalytic oxidative desulfurization of dibenzothiophene(DBT)and benzothiophene(BT)from model fuel.Up to a threshold PMV loading,the mZrO2 revealed improved stability,while the hybrid cataly'sts had both Br(?)nsted and Lewis acidic sites.The oxidative desulfurization abilities of xPMV/mZrO2 were further enhanced with Pd-promotion,achieving with>99.0%and 97.7%for DBT and BT conversion.Catalyst was reusable,and high catalytic activity was maintained over 10 cycles,making it a promising bifunctional catalyst for oxidative deep desulphurization of liquid hydrocarbon fuels.