The Exploration Of New Methods For Fabrication Of Metal-Organic Frameworks

Metal-organic frameworks（MOFs）are porous crystalline materials constructed by metal ions or clusters with organic linkers.MOFswith high surface area,well-defined pores,rich structural diversity and functionality have great potentials in applications likegas separation/storage,catalysis,sensing and pollutant treatment.However,as a kind of crystalline materials,they can easily break down into tiny particles or powders,which would hamper their industrialapplications.For instance,catalysis or seperation processes using MOF crystals can be severely affected by catalyst loss and pipe clog or even explosion might occur.The exploration of novel methods for the fabrication of MOFs based devices is necessary while largely unmet.This paper is mainly focused on three device-fabrication methods,hot-pressing,freeze-drying and electrospinning.（1）For hot-pressing strategy,we have conducted two parts of work.In the first part,we reported an alternative facile and scalable hot-pressing（Ho P）method for MOF coatings generally applicable to various substrates.Devices obtained via this Ho P method exhibit excellent uniformity and robustness with well-maintained crystallinity and microporosity of the pristine MOFs.In the second part,we reported a versatile and scalable roll-to-roll hot-pressing strategy for mass production of MOF-based filters（MOFilters）.This strategy has been applied in different MOF systems（i.e.ZIF-8,ZIF-67 and Ni-ZIF-8）and on various substrates（i.e.plastic mesh,glass cloth,metal mesh,nonwoven fabric and melamine foam）.The obtained MOFiltersshowed excellentrobustness,a broad working temperaturerange（from 80 ^oCto 300 ^oC）andsuperior PM removalefficiencyatbothroomtemperature(e.g.,ZIF-8@Melamine foam,PM_2.5:99.5±1.7%;PM₁₀:99.3±1.2%)and 200 ^oC(e.g.,ZIF-8@Glass cloth,PM_2.5:96.8±1.3%;PM₁₀:95.8±1.4%).Such versatile MOFilterscanbepurposelydesignedandappliedin variousapplicationscenarios.These high performance MOFilters,along with the roll-to-roll mass production protocol,are very promising for PM pollution control in both residential and industrial environments.（2）For freeze-drying,we also did two parts of works.In the first part,wecombined HKUST-1@Fe₃O₄ nanoparticles with CMC to form a kind of magnetic fluid and presented a facile strategy to transform this fluid to gel and shaped bodies without changing the underlying topology of the MOF.And further we freeze dried various MOFs based gel to yield foams with low densities and hierarchical porosities.These foams exhibited excellent robustness that could resist taping and mechanical stirring and displayed excellent catalytic performance.In the second part,we reported a facile templated freeze-drying protocol for the fabrication of MOF based hollow tubes for pollutants removal.Five representative MOFs were picked to produce various kinds of hollow tubes（e.g.,“Janus”,“coaxial”and“cellular”）to treat pollutants in liquid or air.（3）For electrospinning,in this part of work we reported a general method for size-control of Lanthanide MOFs utilizing various nitrogenous heterocyclic modulators.With the size-reduction from micrometers to nanometers,defects were largely exposed and catalytic performance of MOF was significantly improved compared with that of its bulk-phase.Furthermore,nano-sized Lanthanide MOFs could be processed into coating catalysts（suitable to various substrates）through electrospinningwith excellent catalytic activity,which holds great potentials in batch or continuous-flow catalytic processes.Overall,this paper is focused on thefabrication of MOFs into various devices through three kinds of powerful methods.Furthermore,we applied these devices in applications like efficient catalysis or pollutant removal.