Synthesis And Properties Of Novel Porous Frameworks Using N-2-Aryl-1,2,3-Triazole

Porous materials including metal-organic frameworks(MOFs)and covalent-organic frameworks(COFs)have been widely applied in gas adsorption and separation,drug delivery and fluorescent sensor because of controllable surface area,designable pore size,tunable pore shapes and predictable topology.At the same time,ligand geometry such as steric hindrance and rotation on backbones would dramatically has influence on crystal growth and final topology(pore size and pore volume).Multi-carboxylate ligands have been extensively introduced for MOF construction through the COO^-coordination with various metal cations especially biphenyl and terphenyl backbones.In terms of bis-benzene systems,twist conformation is observed in almost all cases due to the strong A-1,3 repulsion between adjacent benzene rings,which will reduces the degree of crystallization.For terphenyl systems,A-1,3 repulsion between the ortho-protons on adjacent benzene rings will result in two conformations:1)twisted(all three rings twisted)and 2)orthogonal(rings 1 and 3 are parallel and twisted the same angle with the middle benzene).Therefore,it is urgent to design and synthesize co-planar ligand to facilitate rigid porous frameworks.1,2,3-triazole has been a series of multifunctional N-heterocycle molecules owing to distinct physical-chemical properties,such as chemical inert,high aromatic stability and degradation-resistance.Meanwhile,1,2,3-triazole is able to be incorporated into hydrogen bond formation and dipole-dipole interactions.As a result,this paper aims to design and synthesize N-2-aryl-1,2,3-triazole derivatives for construction and properties of MOFs and COFs.Main results are illustrated as following:(1)NAT-MOF-1 and NAT-MOF-2 were successfully synthesized from coordination between N-2-aryl-1,2,3-triazole derivatives(TADA and TATA)and Zn²⁺clusters.Crystal data confirms that NAT-MOF-1 presents symmetrical framework with dinuclear paddle-wheel secondary building units(SBU),where NAT-MOF-2 generates the interpenetrated networks with“roof-tile”alignment.NAT-MOF-1 and NAT-MOF-2present desirable thermal stability even after removing guest molecules.In addition,coordination between carboxylates and Zn²⁺restricts the rotation of carboxylates and in reverse increases fluorescent intensity after formation of frameworks.Therefore,NAT-MOF-1 appears individual selectivity for detection of TNP over other nitroaromatic explosives by fluorescent quenching mechanism(K_sv=4.87×10⁴,LOD=1.79×10^-5 M),suggesting potential values in fluorescent sensor.(2)1,4-Bis-triazole-substituted arene(NAT-COOH)was obtained for the fabrication of NAT-MOFs with Cu²⁺and Cd²⁺.NAT-COOH presents energetically favored co-planar conformation(dihedral angle<30°).NAT-MOF-Cd(2,3,4-c)was formed by six-coordinated Cd²⁺clusters with two types of NAT-COOH.In detail,C4,C5-substituted carboxylates from NAT-COOH-1 were all involved into coordinate with Cd²⁺,while half of carboxylates from each side were joint to coordinate with Cd²⁺to construct so-called NAT-COOH-2.Interestingly,uncoordinated carboxylates from NAT-COOH-2 forms lay-by-layer hydrogen bonded frameworks.Such framework not only enhances fluorescent intensity,but also decreases the stability.NAT-MOF-Cu(4-c)was composed of Cu²⁺paddle-wheel SBU with increasing stability(p H=1-11)and BET surface area,suggesting desirable catalytic activity of epoxide cycloaddition towards epichlorohydrin.In summary,such catalytic activity broadens catalytic applications for NAT-MOFs.(3)Novel aldehyde functionalized 1,4-bis-triazole-substituted arene(NAT-CHO)was obtained for COF construction.NAT-COF was produced by NAT-CHO and tetrakis(4-aminophenyl)ethene(ETTA)through polycondensation.Meanwhile,NAT-COF with AA stacking gives high chemical stability when being immersed in aqueous solution(p H=5-13)after 15 days.In addition,extended backbond of polar NAT-CHO and lipophilic ETTA endow NAT-COF efficient gas adsorption behaviours.NAT-COF presents high selectivity between C₃H₈ and CH₄(199.5 at 273 K and 190 at298 K).Furthermore,dipole-dipole interactions between NAT-COF and CO₂ also bring considerable selectivity of CO₂/N₂ and CO₂/CH₄.The synthesis and gas adsorption of NAT-COF facilitate future fabrication and applications of new COFs.