Controllable Synthesis Of Hierarchical Mesoporous/Microporous Nitrogen-rich Polymer Networks Andnitrogen-rich Carbons For Adsorption

Hierarchically porous structure provides synergies between transport properties and enhanced surface. Integrating permanent microporosity (<2nm) with three-dimensional (3D) continuous mesopores (2--50nm) or macropores (>50nm) is of particular signicance for adsorption and catalysis because it combines high specie surface area with high pore accessibility desired. Herein, a facile and scalable one-pot approach has been developed for the preparation of hierarchical meso-and microporous nitrogen-rich polymer networks by sol-gel polymerization of melamine, resorcinol and terephthaldehyde. The resulting nitrogen-rich porous carbons were obtained by the direct carbonization of the as-prepared polymer. The CO2adsorption performance of as-synthesized polymers and carbons were evaluated. The major conculsions are summaried as follows.1) We demonstrated a facile method to prepare the hierarchical nitrogen-rich porous polymer, which combining the micropores formed from a network of rigid polymer chains with the meso-/macropores formed fromthe reaction-induced sol-gel phase separation. After carbonization, the hierarchical nitrogen-rich porous polymer was converted into the nitrogen-rich carbon materials with hierarchically porous structure. The meso-/macropores were partially inherited from the polymer, while the micropores insides the carbon nanoparticles were formed by the volatilization of light molecule during pyrolysis.2) The addition of hexafunctional melamine to the polymer precursor could enhance the crosslinking degree at a molecular level, thus leading to more accessible micropores within the networks. It can also increase the size of polymer clusters, leading to the formation of larger mesopores. Moreover, the nitrogen functional groups inherited from melamine can also be adjusted by changing the precursor composition. The nitrogen content in the polymer network can be adjusted from21.9wt.%to34.3wt.%by chaning the ratio of M/R from1to4.3) Theobtained polymer networks have hierarchical porous structure with moderate microporous surface area and high mesoporous volume. The average mesopore size increased with the M/R ratio. The highest surface area of polymers can up to680m2/g at the M/R ratio of3, while the microporous volume can reach0.24cm?/g. The uptakes of CO2gradually increases with the M/R ratio, exhibiting the maxmium of2.3mmol/g at273K and2.08mmol/g at298K. The polymer networks also exhibited high adsorption capacity for Cr(VI)ions with the maximum of126.3mg/g.4) The nitrogen-rich porous carbons were obtained by the direct pyrolysis of the polymer networks. The surface areas and the total volume of porous carbonscan reach1150m2/g and1.58cm3/g, respectively, while the nitrogen content doped into the carbon framework can reach14.5wt.%. The CO2uptake of the as-prepared carbons can maintain3.99mmol/g at273 K and2.99mmol/g at298K.