Preparation And Properties Study Of Microporous Organic Polymers Containing Carbon Dioxide Adsorption Active Site

In recent years，greenhouse effect become increased year by year with the developmentof economy and the slather use of fossil fuels leading to large amounts of greenhouse gasemission, thus it is a big challenge that control carbon dioxide emissions and capturecarbon dioxide from the atmosphere in order to reduce the content of carbon dioxide in theatmosphere. In recent years, the rapid development of solid microporous materials withhigh specific surface area provides a broad application prospect for CO2adsorption andstorage. Microporous organic polymers (MOPs) is a class of new physical adsorptionporous solid material, and mainly composed of low density elements (for example, C, H, O,N, B, etc.). Recently, microporous organic polymers (MOPs) have been demonstrated asthe competent candidates for hydrogen storage, gas separation, catalysis carbon and dioxidecapture and storage at ambient temperature and so on due to their large surface areas, goodphysical and chemical stability, pore surface modifiability, and synthetic diversification.For how to improve the CO2adsorption amount of materials, in previous studies, inaddition to increasing the specific surface area, adjusting pore size which are allconventional methods. However, recent studies have found that the microporous organicpolymer containg active sites may break the routine, even if with a low specific surface areacan be obtained a high CO2uptake. Therefore, the main task in our work is that the activesites were introduced into the material.In this paper, a series of microporous organic polymer was synthesized by the methodof the Friedel-Crafts crosslinking reaction and Scholl Coupling using monomer containingCO2adsorption active sites functional groups(-OH, N). Microporous organic polymer werecharacterized using infrared spectrum (FT-IR IR), solid nuclear magnetic (13C CP/MASNMR), scanning electron microscopy (SEM), specific surface area and pore size analyzeretc.. The influence of the active site on the specific surface area of polymer, CO2adsorption capacity and the CO2adsorption heat, etc. were discussed. The obtained results are asfollows:(1) We select containing–OH monomers such as phenol, hydroquinone, resorcinol,catechol, to synthesize polymers containing different numbers and location hydroxylgroups by the Friedel-Crafts reaction, whose corresponding product are HCP-Ph、HCP-Hy、HCP-Re、HCP-Ca respectively. The effect of ratios of monomer with FDA and functionallocation and types on specific surface area, CO2storage and CO2heats of adsorption werestudied and discussed for HCPs. At present, these polymers is a kind of materials with thehigh CO2adsorption heat but low specific surface area. The polymer Ca-1has the highestCO2uptake up to11.4wt%at273K and1bar and its BET surface area is393m2/g. Heatsof adsorption for CO2of polymers were calculated by testing CO2storage at273K and298K. The CO2heats of adsorption for polymers HCP-Ph, HCP-Hy, HCP-Re, HCP-Ca are27.1KJ mol-1,29.2KJ mol-1,33.7KJ mol-1,35.7KJ mol-1respectively. The adsorption heatdatas show that the hydroxyl number in monomer is more or the position of the twohydroxyl groups are closer, CO2adsorption heat of the material is lager; As the proportionof monomers with FDA increased from1:2to1:3, polymers HCP-Ph, HCP-Hy, HCP-Re,HCP-Ca for CO2adsorption capacity (273K@1bar) from9.4wt%,10.5wt%,8.0wt%,11.4wt%respectively decreased to9.0wt%,8.4wt%,6.4wt%,10.3wt%. Obviously,monomer with the FDA ratio of1:2is the best proportion.(2) A series of microporous organic polymers were synthesized by selecting thearomatic heterocyclic monomer containing N atom, such as: triphenylamine, carbazole,indole, AlCl3as catalyst using Scholl Coupling method, corresponding to resultinghomopolymers product: PTBA, PCA and PIN. The copolymers PCA-TBA、PCA-IN andPIN-TBA were synthesized by copolymerization of two monomers. And, the effects ofnitrogen atom on CO2adsorption performance were discussed. The highest CO2storage is 16.5wt%(273K@1bar) and its BET surface area is up to629m2/g. Heats of adsorptionfor CO2of polymers were calculated by testing CO2storage at273K and298K. The CO2heats of adsorption of PTBA, PCA, PIN, PCA-TBA, PCA-IN, PIN-TBA are29.8KJmol-1,24.4KJ mol-1,30.6KJ mol-1,26.5KJ mol-1,24.8KJ mol-1,26.9KJ mol-1respectively. Polymers PTBA, PCA, PIN, PCA-TBA, PCA-IN, PIN-TBA for CO2adsorption capacity (273K@1bar) are13.6wt%,15.6wt%,10.8wt%,14.8wt%,16.5wt%,14.2wt%respectively. It been founded that protoned-nitrogen atom (NH) has morestrong hydrophilic carbon performance than the nitrogen atom (N) within polymerframeworks by comparing CO2adsorption capacity of PTBA, PCA-TBA, PIN-TBA.These results confirmed that the introduction of the hydroxyl and nitrogen groups intomicroporous polymer is a effective method to give microporous polymer with affinity CO2active sites and design and preparation of high CO2uptake of microporous materials laidthe foundation for the future.