Preparation And Properties Of Molecularly Imprinted Covalent Organic Frameworks In Ion Extraction

Covalent organic frameworks（COFs）are a new class of crystalline organic porous materials,which connected by covalent bonds with periodically expanded network.COFs composed of light elements show large specific surface are,adjustable pore size,and excellent modifiability,which are widely investigated in the fields of separation of ions.However,target synthesis of COF-based adsorbents with high selectivity,large sorption capacity,and fast kinetics has historically been a hard problem.In this work,covalent organic frameworks are utilized as scaffold;by introducing the construction strategy of molecularly imprinted technology（MIT）we prepare series of ion adsorbents with excellent performance.The main contents are listed in the following:1.To develop absorbent materials with high selectivity and fast adsorption kinetics in acidic solution,the molecularly imprinted technology as the basic build policy,and the C-N linked COFs（Tp Pa-COF and Tp Bd-COF）are utilized as host materials,to integrate poly2,5-dihydroxy-1,4-benzoquinone-3,6-methylene（PDBM）containing carbonyl and hydroxyl groups by the method of copolymerization,namely molecular imprinted PDBM@COF（PDBM@Tp Xx-COF）.The adsorbents are characterized by X-ray diffraction,infrared spectroscopy,thermogravimetry and scanning electron microscopy,etc.The hydroxyl and carbonyl groups in PDBM coupled with C-N groups in COFs chelate with uranyl ions.They reach 73 mg/g of uranyl adsorption capacity in 60 min adsorption equilibrium time.2.In order to obtain an absorbent material with high adsorption efficiency from seawater,we integrate polyketones（PAP）into porous channels of COFs by the method of homopolymerization to serve as the adsorption sites.Using the ionic template technique,the selective recognition sites were tailored.The resulting covalent organic frameworks（COFs）exhibit high affinity toward uranyl ions,which show a high uranyl extraction capacity of 275mg/g.In addition,the ion competition experiments show that the PAP@MI-Tp Bd has excellent selectivity to uranyl ions with selectivity coefficient of U/V over 42.7.3.To obtain absorbent material with high adsorption efficiency for rare-earth metals(such as Nd³⁺),the covalent organic framework with nitryl groups（Tp Bd（NO₂）₂）as the raw materials.And the Tp Bd（NH₂）₂ as the intermediate by using reduction-after development.Next,combine molecularly imprinted technology with regulation molecules spatial configurations strategy as the basic policy,series of Nd³⁺adsorbents were prepared by using post-translational modifications,named as Tp Bd（NHCOOH）₂,Tp Bd（NH-m-Ph COOH）₂,and Tp Bd（N（COOH）₂）₂.The Nd³⁺adsorption experiments shows that Tp Bd（N（COOH）₂）₂ has a high Nd³⁺adsorption capacity of 3.95 m M/g(10 m M Nd³⁺).In addition,the ion competition experiments indicated that the Tp Bd（N（COOH）₂）₂ shows good selectivity to Nd³⁺ion in rare-earth solution.