MOFs Based On Linear Cluster Secondary Building Units And Their Reactivity

With the increasing in-depth understanding of metal-organic frameworks?MOFs?,chemists have developed post-synthetic modification methods to obtain structures that are not directly accessible through the“one-pot”reaction.Single-crystal to single-crystal conversion?SCSC?involves atomic rearrangement in the solid state without breaking the long-range order.The porous scaffold-like structures of MOFs thus allow an unlimited SCSC possibility because small molecules can penetrate into the pores of the MOFs to facilitate guest inclusion/exchange,metal ion metathesis/incorporation,coordination solvate/linker exchange,and linker modification,without severe framework distortion that would shatter the crystal.In this thesis,we used the benzene-1,3,5-tribenzoic acid?H₃BTB?to react with Cd²⁺and Co²⁺under different conditions to obtain a series of two-/three-dimensional?2D/3D?MOFs,and explored their SCSC reactivity.We also also explored the gas adsorption properties of the product obtained.The key results are briefly described as follows:I)We select a 2D double-layer MOF[Cd₃?BTB?₂?DEF?₄]·xDEF?1;DEF=N,N'-diethylformamide?as the starting material to react with dipyridyl ligands of different lengths and angles,including 4,4'-dipyridyl sulfide?DPS?,4,4'-dipyridyl disulfide?DPDS?and 2-bis?4-pyridyl?ethane?BPEA?to obtain two 3D non-interpenetrated structures[Cd₃?BTB?₂?DPS?₂]·xSol?3?and[Cd₃?BTB?₂?DPDS?₂]·xSol?4?,and one interpenetrated structure[Cd₃?BTB?₂?BPEA??H₂O?₂]·xSol?5?.Subsequently,solvent-assisted linker exchange?SALE?of a documented 3D interpenetrated structure[Cd₃?BTB?₂?BPEE??H₂O?₂]·xSol?2c;BPEE=trans-1,2-bis?4-pyridyl?ethylene?is selected to reacted with 4,4'-bipyridine?BIPY?,4,4'-azopyridine?AZOPY?,BPEA,1,3-bis?4-pyridyl?propane?BPP?,1,4-di?pyrid-4-yl?benzene?DPB?and pyrazine?PZ?,fromwhichaseriesoftopologicallyidenticaldaughterMOFs,[Cd₃?BTB?₂?BPEE??BIPY?₂]·xSol?6a?,[Cd₃?BTB?₂?BPEE??AZOPY?₂]·xSol?6b?,[Cd₃?BTB?₂?BPEE??BPEA?₂]·xSol?6c?,[Cd₃?BTB?₂?BPEE??BPP?₂]·xSol?6d?,[Cd₃?BTB?₂?BPEE??DPB?₂]·xSol?6e?,[Cd₃?BTB?₂?BPEE??PZ??H₂O?]·xSol?7a?,[Cd₃?BTB?₂?BPEE??PZ?₂]·xSol?7b?were obtained,in addition to the non-interpenetrated MOFs 3 and 4 upon its reaction with DPS and DPDS.Ultimately,with the long time exposure of 2c to a large excess of BPEE ligand,a 3D self-interpenetrated structure[Cd₃?BTB?₂?BPEE-a??BPEE-b?_0.25?BPEE-c?_0.25?H₂O?_1.75]·xSol?8;the a,b,and c suffice denote BPEE ligands responsible for interpenetration,self-interpenetration and terminal coordination?is obtained.II)Doping of Co²⁺in MOF 1 results in a 2D heterometallic double-layer compound[Cd_2.25Co_0.75?BTB?₂?DEF?₄]?xDEF?9?with statistical Cd and Co distribution within the linear M₃ SBU.The SCSC conversion of compound 9 with DPS,DPDS,BIPY in CHCl₃ give rise to two 3D non-interpenetrated structures[Cd_2.25Co_0.75?BTB?₂?DPS?₂]?xSol?10?and[Cd_2.25Co_0.75?BTB?₂?DPDS?₂]?xSol?11?,and a 3D interpenetrated structure[Cd_2.25Co_0.75?BTB?₂?BIPY??H₂O?₂]?xSol?12?.III)AsthecontentofCo²⁺increased,a3DMOF[Co₁₁?BTB?₆?NO₃?₄?DEF?₂?H₂O?₁₄]?xSol?13?without Cd²⁺is obtained.MOF 13 is sustained by a rare combination of a linear trinuclear Co₃ and two types of dinuclear Co₂ SBUs in a 1:2:2 ratio with permanent porosity,which has a significant adsorption effect on CO₂.IV)The incorporation of a secondary metal Ca²⁺?in the form of CaSO₄?targeting the heterometallic MOF topologically identical to MOF 1 unexpectedly leads to the isolation of a Cd₅-based 3D MOF of[Cd₅?BTB?₄?DEF?₂]?xDEF?14?.Although the compound contains a large non-linear Cd₅ SBU,significant“breathing effects”can be observed in different solvents and under vacuum.We have succeeded in collecting the single crystal structures in the corresponding products,[Cd₅?BTB?₄?DEF?₂]?xCHCl₃?14-CHCl₃?,[Cd₅?BTB?₄?DEF?₂]?xMeCN?14-MeCN?,[Cd₅?BTB?₄?DEF?₂]?xDEF?14-5h?,[Cd₅?BTB?₄?DEF?₃]?xDEF?14-10h?,[Cd₅?BTB?₄?DEF??H₂O?₂]?xDEF?14-24h?.After immersing MOF 14 in 4-pyridine carboxyaldehyde?PYCA?and 4-acetylpyridine?ACPY?foroneweek,unconventionaladditionproducts[Cd₅?BTB?₄?DEF?₂?PYCA?₂]?xSol?15?and[Cd₅?BTB?₄?DEF?₂?ACPY?₂]?xSol?16?are also obtained obtained.