Synthesis Of High Surface Area Nanosized Boron Ntride For CO₂ Adsorption

Boron nitride,known as "white graphite",possesses excellent physical and chemical properties.The nanostructure boron nitrides,exhibiting abundant pore space,high specific surface,excellent thermal stability and anti-oxidationproperity,have potential application in the fields of CO2 adsorption,hydrogen storage,catalyst carrier,and so on.However,the plentiful preparationof nano structure boron nitridewith high specific surface area are still challenging.In this thesis,using boric acid as boron source,melamine and urea as nitrogen sources,a series of nano structure boron nitrides exhibiting high specific surface were prepared with high productivity.Furthermore,the synthetic parameters,including the precursors,the B/N ratio and pretreatment conditions,were optimized for improving the specific surface area of nano structure boron nitrides and the adsorption performance of CO2.(1)Boric acid as boron source,melamine and urea as mixed nitrogen sources,a series of high specific surface boron nitride nanomaterials were prepared withhigh yield by tuning the ratio of boron to nitrogen source,reaction temperature and reaction time.The BET specific surface area(SBET)of the optimum sample is about 446.4 m2 g-1,the micropore area exceeds 230 m2 g-1,the total pore volume is about 0.26 cm3 g-1.The measurements of CO2 adsorption show that the static adsorption capacity of CO2 is 0.93 mmol g-1 at 298 K and 800 mmHg.(2)Boron trioxide and urea as boron and nitrogen sources,respectively,a series of boron nitride nanomaterials with very high specific surface were prepared by optimizing the ratio of precursors and pretreatment solvent.The SBET of the representative sample is 1431.7 m2 g-1,and the micropore surface area is about 782.5 m2 g-1.The adsorption capacity of CO2 reaches 2.39 mmol g-1,and its adsorption heat is 29 kJ mol-1,indicating an strong interaction between the adsorbent and the CO2 molecule.These results reveal that nano structure boron nitride with high surface areais a potential adsorbent in the field of CO2 capture.