Design,preparation And Application Of Microporous Carbon Based On Benzoxazine-linked Porous Polymer

Microporous carbon,a novel carbon material linked by carbon skeleton which displays excellent properties of high thermal and chemical stability,acid and alkali resistance,low energy requirements for regeneration,large specific surface area,has been widely applied in hydrogen storage,CO2 capture,electric double-layer capacitors and catalysis.Microporous carbon with the pore size of less than 2 nm,is advantageous in terms of adsorption,separation,catalysis,energy storage and other fields.Microporous carbons with various pore sizes,structures and functional group modifications have been successfully prepared using different methods and carbon sources.But the preparation of high performance microporous carbon materials is still challenging.The specific surface area,pore structure and the number of surface heteroatoms of the microporous carbon are depended on the structure and properties of the precursors Biomass materials,coal petroleum and polymers are common precursors of microporous carbon.Biomass and coal petroleum possess many beneficial properties,such as cheap raw material and easy to obtain.But it is difficult to strictly prepare high-performance microporous carbon.Polymers,are considered as ideal precursors for the synthesis of microporous carbons because of flexible and controllable design,abundant raw materials,and diversification of synthetic methods.Porous polymer with a certain regular pore structure,is advantageous in the preparation of microporous carbon for specific applications(such as high carbon dioxide adsorption)Thus,exploring novel polymer precursors for the efficient synthesis of microporous carbon with large surface area,special pore structure and micro-morphology,and high char yield via a low cost and simple approach is meaningful.Benzoxazine,a novel phenolic heterocyclic resin,has outstanding thermal properties,high carbon yield,no catalyst,no by-products,and molecular design.The oxazine ring is a space-half-type six-membered heterocyclic ring composed of C,N,O,and H elements.Therefore,the oxazine ring can be used as a linking unit to construct porous polymer.This topic is to seek a new type of precursor to prepare microporous carbon with large specific surface area,controllable pore structure and developed micropores.Using benzoxazine as framework linkage,the benzoxazine-based porous polymer TAPB-NDO was synthesized without any catalysts in a mild condition.Then a series of microporous carbons with special morphology structured and excellent pore structure were received by activation with KOH in one step at different temperature(500-900?).These porous carbon materials exhibit excellent properties in terms of carbon dioxide adsorption.Firstly,1,3,5-tris(4-nitrophenyl)benzene(TAPB),1,5-dihydroxynaphthalene(NDO),and formaldehyde(CH2O)were selected to prepare benzoxazine-based porous polymer(TAPB-NDO)with sufficient rigidity at 90? in the absence of catalysts.The nitrogen isotherm adsorption test showed that the specific surface area of TAPB-NDO is 140 m2/g.The pore size of TAPB-NDO is 1.3 nm and 2.6 nm,which presented a multi-stage pore structure(microporous/mesoporous).Thermogravimetric analysis proved that the porous polymer TAPB-NDO had good thermal properties and high residual carbon ratio.TAPB-NDO had a nitrogen content of 6.93%and an oxygen content of 10.52%by the test of elemental analysis,which was an ideal precursor for preparing porous carbon.Secondly,using porous polymer TAPB-NDO as the precursor,a series of microporous carbons were received by activation with KOH in one step at different temperature(500-900?).The surface areas of the products ranged from 601 m2 g-1 to 2176 m2 g-1 and the aperture sizes varied from 0.6 nm to 2 nm.At the same time,TAPB-NDO possessed a certain amount of nitrogen content(4.57%-0.27%)and higher carbon yield(70.20%-25.80%).Finally,the carbon dioxide adsorption of BMCs were investigated.The effect of the mixing mass ratio of KOH and TAPB-NDO on the carbon dioxide adsorption of porous carbon was studied.It was determined that the optimum amount of KOH was twice that of TAPB-NDO.Next,the effect of activation temperatures(500?-900?)on the adsorption performance of porous carbon were investigated.These porous carbons exhibited excellent CO2 capture capacity ranged from 4.02 mmol g-1 to 7.06 mmol g-1 at 273 K(1 bar)and 2.29-4.27 mmol g-1 at 298 K(1 bar).700? was determined to be the most suitable activation temperature.The BMC-700 also showed an excellent N2/CO2 selectivity and good performance on the recyclability of CO2.The low-cost and novel precursor,along with excellent CO2 capture capacity of the actived products,made our porous carbons BMCs promising adsorbents for CO2 adsorption.In this work,a novel porous polymer linked by benzoxazine was successfully prepared,and the high-performance microporous carbon material were obtained by the activation of the precursor TAPB-NDO.The BMCs behaved excellent CO2 capture capacity.