| Heterogeneous catalysis plays a dominant role in chemical and pharmaceutical industry.It is an effective way to prepare heterogeneous catalysts by anchoring homogeneous catalysts into organic crystalline porous supports,including covalent organic frameworks(COFs),hydrogen-bonded organic frameworks(HOFs),and organic cages(POCs).Compared with traditional amorphous polymers,COFs and HOFs linked by covalent bonds and hydrogen bonds show the advantages of certain crystal structures,large specific surface area,adjustable pore size,designable structure,functional diversity,recycled property and flexible post modification.In particular,the flexible molecular design and post-modification synthesis methods make them excellent physical and chemical properties and good application potential in the field of gas storage,catalysis,separation,sensor and so forth.Porous materials with catalytic activity are beneficial to substrate transport and exposure of catalytic active sites,making them superior to non-porous materials in heterogeneous catalysis field.However,it is still challenging to the synthesis of organic crystalline porous materials with excellent catalytic activity and the modification of catalytic active groups on the basis of non-catalytic activity materials.In addition,the design of stable organic crystalline porous materials is also one of the major sticking points.This paper aims to the design and synthesis of stable organic crystalline porous materials,and introducing catalytic elements into the porous materials by means of synthesis and post-modification to achieve efficient catalytic performance.The main research contents are as follows:(1)Two-Dimensional Covalent Organic Frameworks with Cobalt(?)-Phthalocyanine Sites for Efficient Electrocatalytic Carbon Dioxide ReductionA novel phthalocyanine building block,tetraanhydrides of 2,3,9,10,16,17,23,24-octacarboxyphthalocyaninato cobalt(?)(Co(TAPc))was designed and synthesized for the first time.Two-dimensional polyimide-linked phthalocyanine COFs(denoted as CoPc-PI-COF-1 and CoPc-PI-COF-2)have been devised and prepared through the solvothermal reaction of Co(TAPc)with 1,4-phenylenediamine and 4,4'-biphenyldiamine,respectively.The resultant CoPc-PI-COFs with a four-connected sql net exhibit AA stacking configurations according to powder X-ray diffraction studies.The results showed that the two COFs had permanent porosity,thermal stability above 300?,and excellent resistance to a 12 M HCl aqueous solution for 20 days.In particular,the cathodes made up of COFs and carbon black display the similar high CO2-to-CO Faradaic efficiency(FECO)of 87-97%at various applied potentials-0.60?-0.90 V(vs.RHE)in 0.5 M KHCO3 solution.However,in comparison with CoPc-PI-COF-2&carbon black electrode,the CoPc-PI-COF-1 counterpart provides a larger current density(jco)of-21.2 mA cm-2 at-0.90 V associated with its higher conductivity.This cathode also has the high turnover number and turnover frequency,amounting to 277,000 and 2.2 s-1 at-0.70 V during 40 h lasting measurement.It is worth noting that,the electrocatalytic performance of CoPc-PI-COF-1 is superior to most reticular materials reported thus far.The present investigation not only opens a new avenue for constructing diverse phthalocyanine reticular structures,but also clearly discloses the great potential of 2D porous crystalline solids in electrocatalysis.(2)Three-Dimensional Covalent Organic Frameworks with Cobalt(?)-Phthalocyanine Sites for Efficient Electrocatalytic Carbon Dioxide ReductionThree-dimensional(3D)phthalocyanine COFs,3D-MPc-COF,(M=H2,Co,Ni,Cu),have been devised and prepared through the solvothermal reaction of M(TAPc)(M=H2,Co,Ni,Cu)and 1,3,5,7-tetra(4-benzylamino)-adamantane(TAPA)for the first time.The resultant four 3D COFs show permanent porosity,thermal stability above 300?.The cathodes made up of 3D-CoPc-COF and carbon black display the best electrocatalytic CO2RR performance in four phthalocyanine COFs.Current-voltage curves reveal the conductivity of 3D-CoPc-COF,3D-NiPc-COF,and 3D-CuPc-COF with the value of 2.1×10-4,2.9×10-4,and 2.5×10-3 S m-1,respectively.Although the conductivity of 3D-CoPc-COF is much lower than that of two-dimensional COFs,ultra-high electrochemical surface concentration(1.83× 10-7 mol/cm2)and metal electrochemical activity(32.7%)endow 3D-CoPc-COF with excellent electrocatalytic CO2RR performance.3D-CoPc-COF&carbon black displays high CO2-to-CO Faradaic efficiency(FEco)of 88-97%at various applied potentials-0.60?-1.00 V(vs.RHE)in 0.5 M KHCO3 solution.Furthermore,the current density(jCO)of-30.6 mA cm-2 at-0.9 V(vs.RHE)is superior to COFs reported thus far under the similar experimental conditions.This cathode also has the high turnover number and turnover frequency,amounting to 57,921 and 0.59 s-1 at-0.80 V during lasting tests for 30 h.The present investigation not only presented the first three-dimensional phthalocyanine COFs,but also clearly revealed the huge application potential of three-dimensional COFs in electrocatalysis.(3)Post-Synthetic Metalation of Robust Hydrogen-Bonded Organic Framework for Heterogeneous CatalysisIn the present work,a robust porous HOF(HOF-19)with a Brunauer-Emmett-Teller surface area of 685 m2 g-1 was reticulated from a cage-like building block,amino-substituted bis(tetraoxacalix[2]arene[2]triazine),depending on the hydrogen bonding with the help of ?-? interactions.The post-synthetic metalation of HOF-19 with palladium acetate retains porous hydrogen-bonded structure of HOF-19,exhibiting excellent catalytic performance for Suzuki-Miyaura coupling reaction with the high isolation yields(96?98%),prominent stability,and good selectivity.More importantly,by simple recrystallization,the isolation yield of the deactivated catalyst can be recovered from 46%to 92%,for 4-bromobenzonitrile conversion at the same conditions,revealing the great application potentials of HOF-based catalysts.The present investigation showed the first HOFs based on organic cages,which would be of broad interest among materials science,chemistry,porous materials and catalysis. |
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