Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications

Abstract

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO₂ capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh₃)₄. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (T_d10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m² g^-1), high CO₂ adsorption (5.40 mmol g^-1 at 273 K), excellent capacitance (735 F g^-1), and a capacitance retention of up to 95% after 2000 galvanostatic charge-discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C.

Keywords: energy storage; polybenzoxazine; porous organic polymers; ring-opening polymerization; zeolitic imidazolate frameworks.

Scheme 1

Synthesis of (b) AP-BZ and (c) PA-BZ POP precursors from (a) apigenin.

Figure 1

(a,b) ¹H and (c,d) 1³C NMR spectra of (a,c) apigenin and (b,d) PA-BZ in DMSO-d₆.

Figure 2

(a) DSC and (b) in situ FTIR spectral analyses of the uncured PA-BZ and the PA-BZ thermally polymerized at various curing temperatures to form poly(PA-BZ).

Figure 3

TGA analyses of the uncured PA-BZ and the PA-BZ cured at various temperatures.

Figure 4

(a) FTIR spectrum, (b) solid state ¹³C CP/MAS NMR spectrum, (c) DSC trace, and (d) XRD profile of PA-BZ POP, recorded at room temperature.

Scheme 2

Synthesis of (a) PA-BZ POP/ZIF-67, (b) PA-BZ POP/Metal Composite and (c) PCMC through Sonogashira coupling reaction, etching and pyrolysis process.

Figure 5

XRD profiles of (a) PA-BZ POP, (b) ZIF-67, (c) PA-BZ POP/ZIF-67, (d) PA-BZ POP/metal composite, (e) MPC, and (f) PCMC, recorded at room temperature.

Figure 6

TGA profiles of the (a) PA-BZ POP, ZIF-67, PA-BZ POP/ZIF-67, and PA-BZ POP/metal composite and (b) PA-BZ POP, MPC, and PCMC.

Figure 7

(a–c) N₂ adsorption/desorption isotherms of (a) MPC, (b) ZIF-67, and (c) PCMC. Pore size distribution of (d) MPC, (e) ZIF-76, and (f) PCMC. (g–i) SEM and (j–l) TEM images of (g,j) MCP, (h,k) ZIF-67, and (i,l) PCMC.

Figure 8

CO₂ adsorption profiles of MPC and PCMC, recorded at (a) 298 and (b) 273 K.

Figure 9

CV curves of (a) PA-BZ POP, (b) PA-BZ POP/metal composite, (c) MPC, and (d) PCMC.

Figure 10

GCD performance of (a) P-AP-BZ POP, (b) PA-BZ POP/metal composite, (c) MPC, and (d) PCMC.

Figure 11

(a) Specific capacitance and (b) stability tests of PA-BZ POP, PA-BZ POP/metal composite, MPC, and PCMC.