Supporting Information  支持信息

Zhenchao Qian, Zhen Wang, Yi Chen, Shengrui Tong, Maofa Ge, Ning Zhao* and Jian
钱振超、王震、陈毅、佟胜瑞、葛茂发、赵宁*、简

Pyromellitic dianhydride (PMDA, 99%), paraformaldehyde (96%) and Bisphenol-A (97%) were purchased from Acros. PMDA was dried at under vacuum for prior to use. Aniline (99.5%) was supplied from J&K and 4,4'-oxydianiline (ODA, 98%) was obtained from Alfa Aesar. Trichloromethane, 1,4-dioxane, sodium hydroxide, anhydrous magnesium sulfate of analytical grade were purchased from Beijing Chemical Works. -Dimethylacetamide (DMAC, , water ) was product from Innochem. Unless otherwise specified, all commercial reagents were used as received.
焦溴二酐（PMDA，99%）、多聚甲醛（96%）和双酚A（97%）购自Acros。PMDA在真空 下干燥 后使用。苯胺（99.5%）由J&K提供，4,4'-氧二苯胺（ODA，98%）由Alfa Aesar提供。分析级三氯甲烷、1,4-二氧六环、氢氧化钠、无水硫酸镁购自北京化工。 -二甲基乙酰胺（DMAC， 水 ）是Innochem的产品。除非另有说明，否则所有商业试剂均按收到时使用。

ODA (4.0 g, was dissolved in DMAC at under atmosphere. PMDA with a 2 mol % excess was portion-wise added into the solution in 2 hours under vigorous stirring. After stirring for 12 hours, a light yellow viscous solution containing PAA was obtained and stored at .
ODA（4.0克， 在 大气下 溶于DMAC 中。在剧烈搅拌下，在2小时内将过量2mol%的PMDA分批加入溶液中。搅拌12小时后，得到含有 PAA的淡黄色粘稠溶液，并储存在 。

Electrospinning was carried out using a TL-01 spinning machine (Shenzhen Tongli Weina Technology Co. LTD, China). The PAA solution was spun from a syringe
使用TL-01纺丝机（中国深圳市同力维纳科技有限公司）进行静电纺丝。PAA溶液由注射器旋转而出
equipped with a 21 gauge needle at a feeding rate of . A drum covered by aluminum foil rotated at for collecting nanofibers. The distance between the spinneret and the collector was and the applied voltage was set at . A constant temperature of was maintained during the electrospinning. Then, the electrospun nanofiber membranes were thermally imidized by heating up to 100,150 , 200, 250 and at a rate of , and staying at each temperature stage for and , respectively.
配备 21 号针头，进给速率为 。一个由铝箔覆盖的鼓， 旋转用于收集纳米纤维。喷丝头和集电极之间的距离为 ，施加的电压设置为 。在静电纺丝过程中保持恒定温度 。然后，通过加热高达100,150、200、250 和速率 ，对静电纺丝纳米纤维膜进行热亚胺化，并分别在每个温度阶段停留和 。

A typical procedure for the fabrication of PINFAs is as follows: polyimide nanofiber membranes were cut into pieces and added to 1,4-dioxane . The mixture was homogenized by a homogenizer at for to form a uniform dispersion. Then, the mixture was poured into a mold, frozen at for , subjected to freeze-drying for and then heated at for in air.
PINFA的制造典型程序如下： 将聚酰亚胺纳米纤维膜切成碎片并添加到1,4-二恶烷 中。混合物通过均质机均 质化 ，形成均匀的分散体。然后，将混合物倒入模具中，冷冻 ，冷冻干燥 ，然后在空气 中加热 。

Benzoxazine was synthesized according to the literature. Bisphenol-A ( mol), paraformaldehyde ( , and aniline were added in a round-bottomed flask and stirred at room temperature for . The mixture was then refluxed for in the flask equipped with a condenser, followed by the addition of of trichloromethane. The solution was washed three times with aqueous solution, and several times with distilled water until a neutral value was showed. The organic phase was dried with anhydrous magnesium sulfate and filtered. The solvent was removed under reduced pressure to obtain benzoxazine
根据文献合成苯并恶嗪。 将双酚A（ mol）、多聚甲醛（ 和苯胺 加入圆底烧瓶中，在室温下搅拌。 然后将混合物 回流到装有冷凝器的烧瓶中，然后加入 三氯甲烷。溶液用 水溶液洗涤三次，用蒸馏水洗涤数次，直到显示中 性值。有机相用无水硫酸镁干燥并过滤。减压除去溶剂，得到苯并恶嗪
as yellowish powder. 为淡黄色粉末。

The fabrication of un-PINFAs was same as that of PINFAs except the heat treatment.
除了热处理外，非PINFA的制备与PINFA相同。

A typical procedure for the fabrication of pbo-PINFAs is as follows: benzoxazine monomer was added into the PI nanofiber dispersion mentioned above. The mixture was frozen at for , and followed by freeze-drying for . The obtained monolith was heated at for to cross-link the benzoxazine
pbo-PINFAs的制备方法如下： 将苯并噁嗪单体加入到上述PI纳米纤维分散体中。将混合物冷冻在 ， 然后冷冻 干燥 。将得到的单体加热以 交联苯并恶嗪

Carbonization was carried out in a furnace at for with a heating rate of 10 in a flow of .
在 炉子中以 10 的热速率 在 .

Scanning electron microcopy (SEM) was performed on a JEOL JSM-7500F at an accelerating voltage of . The specific surface area was determined by Quantachrome NOVA 1200e. The aerogels were degassed at for prior to
在 JEOL JSM-7500F 上以 的 加速电压进行扫描电子显微镜 （SEM）。比表面积由Quantachrome NOVA 1200e测定。 气凝胶在之前脱气

adsorption/desorption measurements at . The surface area was obtained from the adsorption curve by the Brunauer-Emmet-Teller (BET) method. Thermal conductivity was measured on a Hot Disk 2500s thermal constants analyzer, which was based on transient plane sources. The skeletal density was measured by UltraPYC 1200e automatic density analyzer (Quantachrome). The porosity of PINFAs was determined by the following formula:
在 处进行吸附/解吸测量。通过Brunauer-Emmet-Teller（BET）方法从吸附曲线中得到表面积。热导率是在 Hot Disk 2500s 热常数分析仪上测量的，该分析仪基于瞬态平面源。骨架密度由UltraPYC 1200e自动密度分析仪（Quantachrome）测量。PINFA的孔隙率由以下公式测定：

where was the density of the aerogel, and was the skeletal density.
哪里 是气凝胶的密度， 是骨架密度。

The compression and tensile tests were performed on Instron (model 3365) equipped with and load cells. For compression tests, cylindrical samples with diameters of and lengths of were employed, and the strain rate was . A 1000-cycle loading-unloading fatigue test was conducted at a strain of and a strain rate of . Tensile tests were measured at a loading speed of using dumbbell-shaped samples about in width and 10 in thickness. The Young's modulus was taken as the slope of the initial linear portion of the stress-strain curve. Thermogravimetric analysis was operated on Pyris 1 TGA (PerkinElmer, America) at a heating rate of from 50 to in air or nitrogen stream with a flow rate of . Normal incidence sound absorption was measured on PINFAs with thickness of by type SW 466 Impedance Tubes, a production of BSWA Technology Co., Ltd. (China), according to the ISO10534-2 standard (ISO, 1998). ATR-FTIR spectra were collected with a BRUKER TENSOR 27 FTIR spectrometer. Raman spectra were obtained on a DXR Raman microscope (Thermo Fisher Scientific Inc.). XPS measurements were carried out with a Thermo Scientific ESCALAB 250Xi using monochromated Al Ka radiation.
压缩和拉伸试验在配备 称重传感器的 Instron （型号 3365） 上进行。对于压缩试验，采用直径和长度为 的 圆柱形样品，应变率为 。在应变和 应变速率下 进行了 1000 次循环的装卸疲劳试验。拉伸试验是在 使用宽度约为 10 的哑铃形样品的加载速度下测量的。杨氏模量作为应力-应变曲线初始线性部分的斜率。在Pyris 1 TGA（美国珀金埃尔默）上以50的升温速率 对 空气或氮气流进行热重分析，流速为 。根据 ISO10534-2 标准（ISO，1998 年），在 BSWA Technology Co.， Ltd. （China） 生产的 SW 466 型阻抗管上测量了厚度为 SW 466 型阻抗管的 PINFA 的正常入射吸声。使用布鲁克 TENSOR 27 FTIR 光谱仪采集 ATR-FTIR 光谱。拉曼光谱是在DXR显微拉曼显微镜（Thermo Fisher Scientific Inc.）上获得的。XPS 测量是使用 Thermo Scientific ESCALAB 250Xi 使用 单色 Al Ka 辐射进行的。

Evaluation of filtration performance: Heavily polluted air in hazy days in Beijing relative humidity, February 2017) with concentration of above was fed at a velocity of through a piece of sample immobilized by a flange. The concentration of was tested by TSI Dusttrak Aerosol Monitor 8532 handheld. The filtration efficiency was calculated using the
过滤性能评价：北京 朦胧天气中重污染空气相对湿度，2017年2月） 以流经法兰固定的一块样品的速度 送入。通过TSI Dusttrak Aerosol Monitor 8532手持式测试了浓度 。过滤效率的计算方法是使用
following equation: 以下等式：

where and represent the mass concentration of before and after filtration, respectively. Pressure drop was tested by TSI 8130 (TSI Inc., MN, USA) with a velocity of . The number concentration of in the range of before and after filtration was evaluated by Scanning Mobility Particle Sizers (SMPS, including a differential mobility analyzer (DMA, TSI 3081), a condensation particle counter (CPC, TSI 3776), and an electrostatic classifier (EC, TSI 3080)).
其中 和 分别表示过滤 前和过滤后的质量浓度。TSI 8130（TSI Inc.，明尼苏达州，美国）测试了压降，速度为 。通过扫描迁移率粒径测定仪（SMPS，包括差动迁移率分析仪（DMA，TSI 3081），冷凝颗粒计数器（CPC，TSI 3776）和静电分级器（EC，TSI 3080））评估过滤 前后范围内的 数值浓度。

Figure S1. SEM image of PI nanofibers with an average diameter of .
图 S1.平均直径为 的 PI 纳米纤维的 SEM 图像。

Figure S2. Photograph of the dispersion of PI nanofibers in dioxane and SEM image of the PI nanofibers cast on the glass from the dispersion.
图 S2.PI纳米纤维在二恶烷中的分散照片和PI纳米纤维从分散体投射到玻璃上的SEM图像。

Figure S3. Photos showing the little volume change between the frozen dispersion
图 S3.照片显示冷冻分散体之间的微小体积变化

and the freeze-dried monolith. SEM image of the resultant fibrous cellular
和冻干巨石。生成的纤维细胞的 SEM 图像
architecture. 建筑。

Figure S4. (a) ATR-FTIR and (b) XPS spectrum of PINFAs and un-PINFAs.
图 S4.（a） PINFA和非PINFA的ATR-FTIR和（b）XPS频谱。

Figure S5. Photographs of (a) un-PINFAs, (b) PINFAs, and (c) un-PINFAs and (d)
图 S5.（a） 非 PINFA 和 （b） PINFA 和 （c） 非 PINFA 和 （d） 的照片

PINFAs after sonification in dioxane.
在二恶烷中超声化后的 PINFA。

Table S1. The porosity of PINFAs with different densities.
表 S1.不同密度的PINFA的孔隙率。

The skeletal density of PINFA is .
PINFA的骨骼密度为 。

Figure S6. SEM images of PINFAs with a density of and , d), respectively.
图 S6.密度分别为 和 、 d） 的 PINFA 的 SEM 图像。

Figure S7. SEM image of un-PINFAs without bonding between nanofibers.
图 S7.纳米纤维之间没有键合的非PINFA的SEM图像。

Figure S8. (a) Photographs of un-PINFAs partially recovered from a compressive strain. SEM images of the sample before (b) and after compression (c).
图 S8.（a） 从 压缩应变中部分回收的非PINFA的照片。（b）前和压缩（c）后样品的SEM图像。

Figure S9. TGA curves of (a) the crosslinker polybenzoxazine under nitrogen atmosphere and (b) pbo-PINFAs under nitrogen and air atmosphere.
图 S9.（a）氮气气氛下聚苯并恶嗪的交联剂和（b）氮气和空气气氛下的pbo-PINFAs的TGA曲线。

Table S2. Mechanical performances of different PINFAs.
表 S2.不同PINFA的机械性能。

Figure S10. SEM images of PINFAs after 1000 loading-unloading fatigue
图 S10.PINFA在1000次上下料疲劳后的SEM图像
compressive cycles at of .
的 压缩循环。

Figure S11. Variation of energy loss coefficient, Young's modulus and stress at of of PINFAs during 1000 cycles.
图 S11.1000次循环 期间PINFA的能量损失系数、杨氏模量和应力的变化 .

Figure S12. SEM images of PINFAs after 500 loading-unloading fatigue tensile cycles at of .
图 S12.PINFA在500次装卸疲劳拉伸循环后的 SEM图像 。

Figure S13. (a) Compressive stress-strain curves of PINFAs after being heated at 300
图 S13.（a） PINFAs在300°C加热后的压应力-应变曲线

for . The Young's modulus is and the stress at of is .
对于 .杨氏模量为 ，应 力为 。

The inset shows the macroscopic shape of the sample after the thermal treatment. (b, c)
插图显示了热处理后样品的宏观形状。（二、三）

SEM images of the sample after the thermal treatment.
热处理后样品的SEM图像。

Figure S14. (a) Acoustic absorption coefficient for PINFAs. (b) Thermal conductivity of PINFAs with different densities at ambient condition.
图 S14.（a） PINFA的吸声系数。（b） 不同密度的PINFA在环境条件下的导热系数。

Figure S15. Raman spectrum of carbonized PINFAs. is 0.65 , implying an abundant -carbon content and good electric conductivity.
图 S15.碳化PINFA的拉曼光谱。 为 0.65 ，表示碳含量丰富 ，导电性好。

Figure S16. SEM images of carbonized PINFAs. A weight loss of and a volume shrinkage of occurred after carbonization, giving the resultant carbonized aerogel with a density as low as , and the cellular architecture was retained.
图 S16.碳化PINFA的SEM图像。碳化后 发生了重量损失 和体积收缩，使所得碳化气凝胶的密度低至 ，并且保留了细胞结构。

Figure S17. (a) Normalized resistance of the carbonized aerogels varies under loading-unloading cycle with strain of . Inset: photographs showing the LED was brightened on compression and recovered on release of the carbonized aerogels. (b) Variation of during 15 cycles of compression.
图 S17.（a） 碳化气凝胶的归一化阻力在上下负荷循环下变化，应变为 。插图：照片显示 LED 在压缩时变亮，并在碳化气凝胶释放时恢复。（b） 在15个压缩周期内的变化 。

(1) X. Ning and H. Ishida, J. Polym. Sci., Part A: Polym. Chem., 1994, 32, 1121-1129.
（1） X. Ning 和 H. Ishida， J. Polym.科学，A 部分：Polym。化学， 1994， 32， 1121-1129.