Triarylmethyl-Based Porous Aromatic Frameworks: Design,Synthesis And Properties

Porous aromatic frameworks（PAFs）have potential applications in many fields such as adsorption,separation,catalysis,and optoelectronics owing to their diverse preparation methods and easily adjustable pore properties,and have attracted many researchers to the development of various functional porous polymers.Over the past decade,many organic molecular fragments with specific properties have been introduced into organic frameworks,including porphyrin,pyrene,triphenylphosphine,etc.Triarylmethyl compounds including triarylmethane,triarylmethyl carbonium,triarylmethyl carbanion and triarylmethyl radical,have rich structures and multiple applications.Currently,there are few reports on porous organic frameworks based on triarylmethyl units.In this thesis,we design and synthesis various triarylmethyl porous aromatic frameworks and further explore their structures and properties.The details of the work are as follows:1.Triarylmethyl carbonium salts can be used as Lewis acid catalyst and oxidizer in organic synthesis.However,there is the lack of low atomic economy and difficult recovery.In this thesis,we synthesis the triphenylmethanol-based framework,PAF-200 with tri（4-biphenyl）methanol as substrate by Friedel-Crafts reaction,and obtain the tritylium-based framework,PAF-201,by further acidification.PAF-201 exhibits more efficient Lewis acid catalytic activity than commercial tritylium tetrafluoroborate and can be recycled at least three times.Meanwhile,DFT calculations confirm that the network of PAF-201 possesses a certain tension,which is intrinsically responsible for highly efficient Lewis acid catalytic activity.2.Although it has higher Lewis acid catalytic activity,the oxidation ability of PAF-201is poorer than tritylium tetrafluoroborate.In this thesis,we utilize triphenylmethyl chloride and dichloroalkanes of different lengths as substrates to weave from rigid to flexible three-dimensional organic frameworks that are further transformed into the tritylium-based frameworks,PAF-207BF₄-n（n=1,2,3,4）.The solubilities of the resulting materials gradually increase with increasing the monomer length.Moreover,they exhibit Lewis acid catalytic ability and dehydrogenation activities comparable to commercial tritylium tetrafluoroborate.In particular,this design strategy can be used as a general way to construct soluble porous materials.3.9-Arylfluorenes,as a special category of triarylmethyl compound,have been used to prepare conductive,luminescent,and magnetic materials.In this thesis,we prepare porous aromatic frameworks with 9-arylfluorene and triarylmethane as the main structural units and explore their performances as the anode materials of alkali metal ion batteries.Especially,PAF-202 exhibit optimal high reversible capacity and electrochemical stability as anode material of lithium-ion battery.The EPR spectra suggest that there exist a small amount of radicals in the frameworks of all these materials.Experimental characterizations and theoretical calculations indicate that larger microporous volume,higher specific surface area and more radicals are beneficial for electrochemical performances of porous organic frameworks.Moreover,PAF-202 is also suitable as anode materials for sodium ion batteries and potassium ion batteries.This work is of high interest for the design of future anode materials for alkali metal ion batteries.