Design,Synthesis And Application Of Pyrene-based Covalent Organic Frameworks

Energy crisis and environmental pollution are two major problems facing today's society,which have affected the development of economy.Solar energy is a kind of inexhaustible renewable energy.How to utilize solar energy efficiently has become a hot research topic in many fields.Covalent organic framework materials(COFs)as a new type of organic porous material exhibit some unique characteristics,such as the diverse modification and functionalization,large specific surface area and porosity,high thermal and chemical stability,permanent open pore structure,diversification of synthetic strategy.Because of these advantages,COFs have received extensive attention and been applied in the field of catalytic technology,gas separation and storage,photoelectric material,environment and energy.The diversity,design and controllability of COFs in the synthesis process make it possible to accurately regulate the structure of COFs at the atomic level and further study the structure-activity relationship of COFs in applications.It is of great significance to understand the mechanism of related action at the micro level.In this paper,three cases of COFs(PY-DHBD-COF,PY-2,2'-BPY-COF,PY-3,3'-BPY-COF)were designed and synthesized by precise regulation of pyrene-based COFs,and their structure-activity relationships in the applications of photocatalytic hydrogen evolution and water harvesting from air were studied.The main research is divided into the following two parts:In the second chapter,we present a novel crystalline 2D covalent organic framework(PY-DHBD-COF)for photocatalytic hydrogen evolution.The rich hydroxyl group and the adjacent amine bond on the COF framework function as initial binding sites for Pt species,which were deposited in the scale from single atoms to nanoparticles during the in-situ photo-deposition process.The co-catalyst loaded COF shows an ultrahigh photocatalytic hydrogen evolution activity of 71160?mol g-1 h-1.This work provides a new strategy for the establishment of micro-environment for co-catalyst deposition in the photo-catalysis.In the third chapter,we synthesized two highly crystalline covalent organic frameworks(PY-2,2'-BPy-COF and PY-3,3'-BPy-COF)to explore the performance of water harvesting from air.The results showed that the maximum saturated adsorption capacities of PY-2,2'-BPy-COF and PY-3,3'-BPy-COF were up to 0.91 g g-1 and 1.27 g g-1,respectively.We simulated the atmospheric water harvesting ability of COFs when the relative humidity was 80%RH and the temperature was 25?.When the adsorption was saturated,we used light with a solar intensity to conduct the water desorption experiment.Both COFs showed excellent performance,and the harvesting rate of water,the amount of captured water and the rate of desorption water did not decrease after 6 cycles.Applying these two materials to the field of obtaining fresh water resources in marine operations,a large amount of fresh water resources can be obtained without the additional energy input.This work has realized the efficient utilization of solar energy and provided a new way for the acquisition of fresh water resources in marine operations.