Acetic anhydride

Polyurethane foam was obtained from Langfang Zhuosheng Building Materials Co., Ltd. (Langfang, China), with an apparent density of 0.035 g/cm³. Borated phenolic resin was obtained from Anhui Tianyu Plastic Co., Ltd. (Bengbu, China) with a density of 1.30 g/cm³. 1,3,5-Triaminophenoxybenzene (TAB) was obtained from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China). Pyridine, acetic anhydride, acetone, ethanol and anhydrous N-methylpyrrolidinone (NMP) were purchased from Sinopharm Chemical Reagent Beijing Co., Ltd. (Beijing, China). 2,2′-Dimethylbenzidine (DMBZ) and biphenyl-3,3′,4,4′-tetracarboxylic dianydride (BPDA) were obtained from Shanghai Aladdin Industrial Co., Ltd. (Shanghai, China). Dianhydride was dried in vacuum at 125 °C for 24 h before use. All other reagents were used without further purification.

Rice straw was obtained from Hubei province, China. Absolute C₂H₅OH, CH₂Cl₂, CH₃OH, hydrogen peroxide (H₂O₂), acetic anhydride (Ac₂O), acetic acid (HAc, 99.5%), concentrated sulfuric acid (H₂SO₄) and potassium hydroxide (KOH) were purchased from Sinopharm Group Chemical Reagent Co. LTD. (Shanghai, China) Poly(vinyl pyrrolidone) (PVP, Mw∼1,300,000), commercial cellulose and commercial cellulose acetate were purchased from Aladdin Regent Company. (Shanghai, China).

Balsa wood was purchased from Guangzhou Sinokiko Balsa Co., ltd. Sodium hydroxide (NaOH, >95%), sodium sulfite (Na₂SO₃, >98%), sodium chlorite (NaClO₂, 80%), ethylene glycol (≥99%), N-methyl-2-pyrrolidone (NMP, 98%), pyridine (>99%), 1,2,4,5-benzenetetracarboxylic anhydride (PMDA, 99%), and 2,2′-Bis(trifluoromethyl)benzidine (TFMB, 98%) were provided by Macklin. The dehydrating agent acetic anhydride (AR) was purchased from Sinopharm. The crosslinker 1,3,5-tris (4-amino phenoxy) benzene (TAB, ≥98%) was purchased from Aladdin. Deionized water (DI) was self-made in the laboratory. All reagents were used without further purification.

Shatian pomelos commercially available from Meizhou (Guangdong, China) were procured in their fresh and ripe state (harvesting season was November), ensuring that they were free from any pests or diseases. The fresh fruits were then meticulously cleaned and peeled, and the peels were diced into uniform small pieces. These pieces were freeze-dried, ground through an 80-mesh sieve, and preserved at 4 °C until use. Enzymes such as high-temperature-resistant α-amylase (500 U/g) and glucoamylase (1.0 × 10⁵ U/mL) were acquired from Aladdin Reagent Co. Ltd. (Shanghai, China). Additionally, papain (800 U/mg), cellulase (green xylanase, 400 U/mg), and Nile red were purchased from Shanghai Yuanye Biotechnology Co. Ltd. (Shanghai, China). Soybean oil was obtained from a Supermarket in Wuhan (Hubei, China), and acetic anhydride was sourced from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

Bi(NO₃)₃·5H₂O and La(NO₃)₃·6H₂O were provided by Shanghai Aladdin Biochemical Technology Co., Ltd., and Fe(NO₃)₃·5H₂O, Ni(CH₃COO)₂·4H₂O, 2-methoxyethanol, acetic acid, ethanolamine, and ethanol anhydrous were purchased from Shanghai Macklin Biochemical Co., Ltd. Acetic anhydride was purchased from Sinopharm Chemical Reagent Co., Ltd.