Porous Organic Catalysts: Designed Synthesis,Characterization,and Catalytic Application

Due to their concise synthesis,unique frameworks,diverse building blocks,and favourable recyclability,porous organic catalysts have been palying important roles in thermaldynamic catalysis,photocatalysis,and chiral catalysis.Besides,porous organic catalysts can assemble the organocatalysts/ligands in frameworks,and can provide an effective solution to the vital problems(e.g.costly preparation,high loadings and tedious separation procedures)in the industrialization process of organocatalysis.However,construction of efficient and stable porous organic catalysts and their structure-activity relationships studies still remain an important challenge.The research contents in this thesis manily focus on the designed synthesis of porous organic catalysts via the?application-oriented?strategy.First,various chiral organocatalysts or photoactive building blocks were incorporated into the frameworks of amorphous or crystalline porous materials on the basis of?bottom-up?or?post-synthesis?strategy.Then,these porous catalysts were applied to the asymmetric catalysis and photocatalysis,and their structure-activity relationships were also studied.The major results were summarized as follows:?.Construction of chiral porous polymer(CPP)catalyst for asymmetric catalysisWe exploited the?bottom-up?strategy to synthesize a TADDOL-functionalized chiral porous polymer(TADDOL-CPP)for asymmetric catalysis and the structure-activity relationship study.As revealed by characterizations,the TADDOL-CPP possesses hierarchical porous structure,high BET surface area,together with abundant and uniformly-distributed catalytic sites.In the presence of Ti(Oi-Pr)₄,TADDOL-CPP acts as a highly efficient and recyclable(at least 11 iterative cycles)catalyst in the asymmetric addition of Et₂Zn to Ar CHO(upto 96%yield and 94%ee).Using the¹³C-labeled Ph¹³CHO as substrate,we monitored the generation and transformation of ¹³C-labeled intermediates through solid-state NMR spectroscopic,and further revealed the catalytic mechanism of the chiral porous organic material.?.Synthesis and catalytic application of chiral/photoactive two-dimensional covalent organic frameworks(COFs)(1)Aiming at the preparation of natural products or pharmaceutical molecules via chiral porous organic catalysts,we designed and synthesized a chiral secondary amine-embeded LZU-85.The experimental results indicated that LZU-85 could promote the asymmetric Michael addition reaction between aliphatic aldehydes and nitroolefin efficiently(up to 99%yield and 87%ee).Furthermore,the catalytic products could be easily converted into(S)-Phenibut,(S)-Bacoflen and other relevant salable drugs.This study provides a new approach for the heterogeneous synthesis of chiral compounds that possess important physiological efficacies.(2)Benefiting from the extraordinary structures of COFs,we developed a class of 2D COF photocatalysts(LZU-80,LZU-81,LZU-82)that possess benzothiazole units and hetero-[6]-radialene nodes.These COFs exhibited high BET surface areas,excellent harvesting ability,and also excellent thermal and chemical stability.In addition,they could catalyze the methyl ketones/nitroalkanes-involved cross dehydrogenation-coupling(CDC)reactions efficiently under visible-light(80-96%yield),and could be resued for at least 8 cycles.Furthermore,we summarized the key factors that affect the photocatalytic performance of POPs by comparison of the efficiency of different porous organic photocatalysts.(3)On the basis of the photocatalysis study above,the light-induced asymmmeric catalysis within COF systems was realized.We tried two strategies,i.e.?one-plus-one?and?all-in-one?,to achieve the transformations.In the presence of LZU-80/LZU-86 and chiral organocatalysts,the?one-plus-one?strategy proved to be worked well for aldehydes/ketones-involved asymmetric CDC reactions(upto 71%ee)and?-alkylation(51%ee).However,the?all-in-one?strategy(LZU-85)showed no activity in the light-induced asymmmeric catalysis,which could be attributed to the structural factors within materials and the limited control effects of chiral groups.The information obtained here provides important approachs for the the application of COFs in light-induced asymmetric catalysis.