The Exploration Of The Application Of Metal-organic Framework Materials In The Treatment Of Waste Plastics

Plastic is widely applied in our daily life because of their low price,handiness and functional diversification,which have conferred giant convenience to human activity.In recent decades,with the increasing demand of plastics,the development for the plastics industry has enormously inspired,causing more and more plastics to be produced every year.Most of discarded plastics with high durability are resistant to biodegradation and can stay in the environment for a long time,thus creating terrifying ecological pollution and economically unfavorable.Therefore,it is great significance for the strategy exploration and the development of materials to manage the plastic pollution which is an urgent problem to be solved.Based on the treatment for the plastic pollution,there are two main strategies:?1?the waste plastic is recycled or degraded into other products with economic value;?2?development the novel degradable plastic replaces the traditional plastic with chemical inertness.Therefore,the search for strategies that can effectively degrade plastics and further convert into products with economic value without causing additional pollution,and the synthesis and development for the novel and easily degradable plastics are long-sought-after.In addition,the microplastics with small sizes in water possessing high specific surface area can strongly absorb contaminants,which causes more serious environmental pollution problems.Therefore,the research with the separation of microplastics from water is also of great significance for the treatment of plastic pollution.Metal-Organic Frameworks?MOFs?,a class of porous crystalline materials constructed from metal ions and organic linkers applied in gas storage/separation,sensing and catalysis.Concerning the construction units of waste polyester plastics are organic ligands like H₂BDC?about 85 wt%in PET?,it will be of tremendous economic value to produce high value-added products like MOFs from waste polyester plastics.The MOFs with superiority in structure tunability,abundant uniformly distributed metal sites,ease of recycling and high porosity and supported on various substrates have attracted broad interest in catalysis,adsorption and separation.The MOFs with improvement and modification is applyed in catalyzing the synthesis of green plastic and the microplastics removal in water,which provide effective solutions and materials for the management of plastic pollution.In this paper,based on the improvement and functional modification of MOFs materials,we propose three effective measures to control plastic pollution.The specific work is as follows:?1?For the first time,we report a kind of POM based plastic hydrolysis protocol for the one-pot syntheses of POMOFs.This protocol can be applied into diverse kinds of polyester plastics?i.e.PET and PBT?and various POM systems(e.g.,polytungstate?Ni₆PW₉?,polyoxomolybdate(Zn₄PMo₁₂)and polyoxovanadate?V₆S?)to generate POMOFs?i.e.Ni-POMOF,Z-POMOF and VMOP-11?with 100%or close to 100%hydrolysis efficiency.POMOFs obtained from such an environmentally friendly method can efficiently catalyze the syntheses of a series of cyclic carbonate compounds?the precursors for polycarbonate plastics?,thus can achieve the conversion from one kind of plastic to another.This new method combined with the increasingly serious plastic pollution problem has broad application prospects in the industrial-grade plastic processing.?2?We synthesize a series of Lanthanum metal-organic frameworks?La-BTB?based highly porous nanospheres through defect engineering and successfully apply them as powerful heterogeneous catalysts in efficient ring-opening polymerization?ROP?of?-butyrolactone??-BL?.Defect engineering can impart these materials with well-tuned morphology?from rod shape to well-tuned porous nanospheres?,tremendous active sites,ultrahigh porosity that are applicable in efficient ROP of?-BL with poly??-butyrolactone??P?BL?yield of about 25%and excellent catalyst reusability.Notably,the obtained P?BL can be completely and quantitatively recycled into monomers by simply heating the product at 220°C for one hour.This works paves a new way to explore powerful heterogeneous catalysts in producing biocompatible and degradable plastics.P?BL can be widely applied and developed to replace traditional plastics with chemically resistant,which can greatly reduce the emissions of traditional plastics and provides a green solution of the treatment for plastic pollution.?3?The series of zirconium metal-organic frameworks?Zr-MOFs?based foam materials?Ui O-66-X@MF,X=H,NH₂,OH,Br and NO₂?have been successfully fabricated with acetone assisted method and applied in the simulated microplastic removal.The variety of MOFs endows these foam materials with high tunability at molecular level and various functional Zr-MOF systems have been loaded onto melamine foam?MF?to achieve integrated foam materials with interpenetrated pore structure,high MOF uniformity,numerous defects and excellent durability.Thus-obtained foam materials have been successfully applied in efficient microplastic removal in water or seawater conditions and can be fitted into various types of microplastics with diverse concentrations.Noteworthy,best of them,Ui O-66-OH@MF-3 can efficiently remove microplastics with efficiency up to 95.5±1.2%and can maintain high performance in recycle?10 cycles?and large-quantity experiments.Besides,we propose an automatic filtration system powered by sunlight and accomplish it in lab-scale.The high performances of these foam materials combine with the new concept of automatic filtration system might shed light on the development of novel techniques for microplastic removal.