Synthesis of highly porous borazine-linked polymers and their application to H2, CO2, and CH4 storage

Abstract

The synthesis of highly porous borazine-linked polymers (BLPs) and their gas uptakes are reported. BLPs exhibit high surface areas up to 2866 m 2 g À1 and can store significant amounts of H 2 (1.93 wt%) and CO 2 (12.8 wt%) at 77 K and 273 K, respectively at 1.0 bar with respective isosteric heats of adsorption of 6.0 and 25.2 kJ mol À1 .Recently there has been great interest in the design and synthesis of highly porous organic architectures due to their multifaceted potential use in applications that include storage, separation, conductivity, and catalysis. 1 The chemical composition, physical and textural properties are dictated during synthesis that allow for materials with enhanced properties relevant to their respective applications. With the exception of microcrystalline covalent-organic frameworks (COFs), 2,3 these polymeric materials are amorphous yet can possess considerable porosity and well-defined cavities which render them highly attractive especially in adsorptive gas storage. 4 Such desirable traits are imparted into organic materials through the use of rigid building blocks that direct the growth of polymer networks without the aid of templating agents. [1][2][3] In addition to customized porosity, polymerization processes can lead to pore wall functionalization that significantly enhance gas uptake and selectivity as we have demonstrated recently for benzimidazole-linked polymers. 5 Alternative methods for improved gas uptake (i.e. hydrogen) by porous architectures can also be accessed by the use of polarizable building units that increase hydrogen-framework interactions. 6 Along this line, we sought after the inclusion of borazine (B 3 N 3 ) as a functionalized and polarizable building block into porous organic polymers. 7 Borazine is isostructural to the boroxine units found in COFs prepared by boronic acid self-condensation reactions 2 and has been mainly used for the fabrication of BN-based ceramics or in organic optoelectronics. [8][9][10] However, up to date, the use of borazine for the preparation of porous polymers for gas storage remains fairly undeveloped.We report herein on the synthesis and characterization of a new class of highly porous borazine-linked polymers and investigate their performance in gas (H 2 , CO 2 , CH 4 ) storage application under low pressure and cryogenic conditions. The synthesis of BLP-1(H) and Scheme 1 Synthesis of BLP-1(H) and BLP-12(H) from in situ thermal decomposition of arylamine-borane adducts.

Synthesis of covalent triazine-based frameworks with high CO2 adsorption and selectivity

“…Finally, 25 introducing the extra rich nitrogen content of benzothiadiazole units into triphenylamine rigid skeleton could result in the strong dipole-quadrupole interactions between CO2 and nitrogen sites, 22,42 which is another reason for the high CO2 absorption. Of course, the CO2 uptake capacities of PCTF-1, PCTF-2 and PCTF- 30 3 are still competitive with those of many reported porous organic polymers with higher BET surface such as furan-based imine-linked POF-1 (7.7 wt%), 43 porous borazine-linked polymers BLP-1H (7.8 wt%), 44 TCMPs (5.4-11.5 wt%), 45 triazine-based polyimide (TPIs) (3.0-10.8 wt%), 46 To gain further insights from the host−guest interaction, Qst (CO2 isosteric heat of adsorption) was obtained with the Clausius−Clapeyron equation from the CO2 adsorption isotherms 40 at 273 and 298 K. All materials showed a high Qst for CO2 (>20 kJ mol -1 ) (Figure 4b) at low coverage, and the Qst is same level to many other MOPs such as some functionalized CMPs (25-29 kJ mol −1 ) 50,51 and COFs (15-30 kJ mol -1 ). [52][53][54] With the increasing quantities of adsorbed CO2, Qst of PCTF-4 retains the highest 45 heats of adsorption, which enhances the capacity of CO2 capture.…”

Methane Adsorption Properties of Mn‐Modified Graphene: A First‐Principles Study

“…Karl et al. [ 9 ] found that a high‐porosity boron–nitrogen polymer (BLPs) had a maximum CH 4 uptake of 18.1 cm 3 g −1 at 273 K. Currently, most of the commonly used CH 4 adsorbents are MOF materials. Liu et al.…”

Microporous Organic Polymers for Carbon Dioxide Capture

“…The borazine ring in these materials is structurally analogous to the boroxine building units found in COFs. Among them, BLP-12(H) exhibits high surface area of 2,244 m 2 g −1 and can store significant amount of CO 2 (12.8 wt%) at 273 K/1 bar [52]. However, any potential materials for CCS require not only high uptake of CO 2 but also excellent selectivity for CO 2 .…”

“…This value is higher than those of reported COFs and only exceeded by the uptake of COF-6 which has much narrower channels (9 Å). Other boron-containing porous materials should include the borazine-linked polymers (BLPs), which is prepared by the thermal decomposition of arylamine-borane or arylamine-boron trihalide adducts in aprotic solvents [52][53][54][55]. The borazine ring in these materials is structurally analogous to the boroxine building units found in COFs.…”