Carbonization and Preparation of Nitrogen-Doped Porous Carbon Materials from Zn-MOF and Its Applications

Nitrogen-doped porous carbon (NPC) materials were successfully synthesized via a Zn-containing metal-organic framework (Zn-MOF). The resulting NPC materials are characterized using various physicochemical techniques which indicated that the NPC materials obtained at different carbonization temperatures exhibited different properties. Pristine MOF morphology and pore size are retained after carbonization at particular temperatures (600 °C-NPC600 and 800 °C-NPC800). NPC800 material shows an excellent surface area 1192 m2/g, total pore volume 0.92 cm3/g and displays a higher CO2 uptake 4.71 mmol/g at 273 k and 1 bar. Furthermore, NPC600 material displays good electrochemical sensing towards H2O2. Under optimized conditions, our sensor exhibited a wide linearity range between 100 µM and 10 mM with a detection limit of 27.5 µM.


Introduction
Porous carbon materials have been regarded as significant porous materials because of their distinctive properties such as pore size, extraordinary surface area and good electrochemical activities [1][2][3]. They have extensive applications in many fields including catalysis, biosensors, fuel cells and supercapacitors [4][5][6][7][8][9][10][11]. In this sense, 3D porous carbon-based structures are promising to numerous applications, such as contamination removal, gas sorption/separation, and electrode materials [2,12,13]. In particular, CO 2 capture purpose nitrogen-doped porous carbon (NPC) materials were used, because of its stability, low cost and performance [14,15]. For CO 2 capture, the pore size of porous material plays a significant role, ultramicropores of~4 Å to~8 Å are predominantly suitable for CO 2 sorption [16,17]. The preparation of porous carbon materials has been synthesized in a known way such as template and activation method [18,19]. Generally, template progression devours a larger quantity of organic or inorganic template and the synthesizing processes are complicated. Activation methods such as KOH and NaOH can afford a high surface area but needed a huge amount of activation agents. To avoid such complication, recently metal-organic framework (MOF) materials have gained tremendous attentions to prepare the porous carbon materials through single step carbonization method. For instance, the recently reported porous carbon material derived from Zn-MOF, having ultramicropore size (~4 Å to~8 Å) showed excellent CO 2 capture properties [20]. Since MOFs have gained tremendous attention due to their diverse structures with tunable pore shapes, sizes, volumes, and surface chemistry. Therefore, MOFs have prospective applications in gas storage/separation, diverse structures with tunable pore shapes, sizes, volumes, and surface chemistry. Therefore, MOFs have prospective applications in gas storage/separation, electronic devices, chemical sensors, catalysis, and biomedical applications [21][22][23][24][25][26]. The multifunctional MOFs are often chosen to synthesis porous carbon materials; MOF-templated straightforward synthesis provided the highquality nanoporous carbon with a well-ordered pore size and significant surface area. The morphology of nanoporous carbon can be tuned by optimizing the carbonization method (such as temperature, time, and atmosphere) [1,27,28]. Recently, MOF-derived metal/metal oxide embedded porous carbon materials [29,30] are used in the electrodes for electrochemical sensors [31,32]. But, maintaining the pristine MOF morphology of the resulting porous materials from the carbonization process is a difficult task due to the shrinkage of framework/decomposing organic ligand during carbonization, therefore, a systematic study is necessary [33].
Additionally, hydrogen peroxide (H2O2) is a toxic oxidizing agent, being used in various fields such as biomedical science, environmental science, food, textile and chemical industries [34][35][36]. Therefore, H2O2 determination is of practical importance for both environmental and industrial purposes. It has been well established that Zn based material modified electrodes are used for H2O2 detection [37,38].

Materials
Zn(NO3)2·6H2O, (98%) and H2BDC, (98%) were bought from Sigma-Aldrich (Burlington, MA, USA), DMF, (≥99.8%) was purchased from Merck (Darmstdt, Germany), (DABCO, 98%) was purchased from Alfa Aesar (Lancashire, UK). All other compounds used throughout this study were of an analytical grade. The electrochemical experiments were performed using a three-electrode system-CHI model 824B workstation with a screen printed carbon electrode (SPCE)/chemically modified SPCE as a working electrode, Ag/AgCl (in 3 M KCl) as a reference electrode, and Pt wire as an auxiliary electrode. SPCE was purchased from Zensor R&D (Taichung, Taiwan). A phosphate buffer solution (0.1 M, pH 7 PBS) was prepared by mixing 0.1 M, NaH2PO4, and Na2HPO4. To compare the various electrodes performance, 5 mM of FeCN solution used as a probe. Briefly, the Scheme 1. Synthesizing pathway of NPC materials from Zn-MOF.

Materials
Zn(NO 3 ) 2 ·6H 2 O, (98%) and H 2 BDC, (98%) were bought from Sigma-Aldrich (Burlington, MA, USA), DMF, (≥99.8%) was purchased from Merck (Darmstdt, Germany), (DABCO, 98%) was purchased from Alfa Aesar (Lancashire, UK). All other compounds used throughout this study were of an analytical grade. The electrochemical experiments were performed using a three-electrode system-CHI model 824B workstation with a screen printed carbon electrode (SPCE)/chemically modified SPCE as a working electrode, Ag/AgCl (in 3 M KCl) as a reference electrode, and Pt wire as an auxiliary electrode. SPCE was purchased from Zensor R&D (Taichung, Taiwan). A phosphate buffer solution (0.1 M, pH 7 PBS) was prepared by mixing 0.1 M, NaH 2 PO 4 , and Na 2 HPO 4 . To compare the various electrodes performance, 5 mM of FeCN solution used as a probe. Briefly, the FeCN solution was prepared using

Preparation of NPC Materials
The NPC materials were prepared through a single-step carbonization method [31]. The 0.400 g of Zn-MOF was transferred into a silica crucible boat and then placed in a furnace chamber. The NPC materials obtained at target temperatures (500, 550, 600, 700, 800, or 900 • C) under an N 2 atmosphere for a 5 h duration. The resulting materials obtained at 500, 550, 600, 700, 800, and 900 • C are assigned as NPC 500 , NPC 550 , NPC 600 , NPC 700 , NPC 800 and NPC 900 respectively.

Characterization
The purity of MOF and NPC materials were investigated by powder x-ray diffraction (PXRD) using a Bruker D8 advance instrument (Billerica, MA, USA) equipped with CuKα radiation (λ = 1.54178 Å). The morphology of MOF and NPC materials were observed by high-resolution scanning electron microscopy (HR-SEM, JEOL JEM-7600F instrument, Akishima, Japan). The NPC materials morphology was characterized by transmission electron microscopy (TEM, using a JEM-2010 instrument, Tokyo, Japan) at a voltage of 200 KV. The synthesized NPC materials were also recorded with a Raman spectra on a CCD detector (Stanford Computer Optics Inc., Berkeley, CA, USA) using a He-Ne laser with an excitation wavelength of 632.8 nm. The Zn element presence was investigated by inductively coupled plasma-mass spectrometry (ICP-MS, Japan Agilent 7500ce, Tokyo, Japan). The elemental analysis (C, N, O) was executed by an elementar vario EL III CHN-OS elemental analyzer (Germany). N 2 gas adsorption, CO 2 gas adsorption of all materials were measured using micrometrics (Norcross, GA, USA) and the gas sorption analysis purpose, the materials were dried at 120 • C for 12 h under vacuum.

Structure, Morphology, and Composition of NPC Materials
Synthesized Zn-MOF structure and porous properties was checked by PXRD, SEM and N 2 gas sorption measurements (Figure 1a-d). As expected, the synthesized MOF showed a well-defined crystallinity and surface area of 1700 m 2 /g, and good agreement with the literature [40]. The pore size of Zn-MOF was calculated by the NLDFT method, it reveals two micropores (0.75 and 1.4 nm) ( Figure 1d). The SEM images revealed the particle shapes of Zn-MOF was a mixture of the cube, brick, and rod-like shapes (Figure 2c). The MOF was further exploited to a one-step direct carbonization method to produce the NPC materials. The detailed preparation method is given in Section 2.3. The morphology, crystallinity and surface area of NPC materials were examined by PXRD, SEM, TEM, Raman analysis, N2 gas sorption isotherms, ICP-MS, and elemental analysis.
The PXRD patterns of the NPC500-700 samples showed the diffraction peaks for the formation of ZnO nanoparticle ( [41]. The NPC500, NPC550, NPC700 morphologies show the shrinking phenomenon of Zn-MOF during carbonization at this particular temperature (Figures S1 and S2). While the morphology retained from pristine MOF, brick, and rod shape at 600 °C (Figures 2d,e and S3). The PXRD pattern of the NPC800 sample showed two broad peaks of graphitic carbon at 23 (002) and 44° (101) (Figure 2b) [7]. The absence of ZnO at higher carbonization temperature revealed when the temperature is close to its boiling point of ZnO (907 °C) is reduced to Zn and evaporate. The MOF was further exploited to a one-step direct carbonization method to produce the NPC materials. The detailed preparation method is given in Section 2.3. The morphology, crystallinity and surface area of NPC materials were examined by PXRD, SEM, TEM, Raman analysis, N 2 gas sorption isotherms, ICP-MS, and elemental analysis.
The PXRD patterns of the NPC 500-700 samples showed the diffraction peaks for the formation of ZnO nanoparticle ( [41]. The NPC 500 , NPC 550 , NPC 700 morphologies show the shrinking phenomenon of Zn-MOF during carbonization at this particular temperature (Figures S1 and S2). While the morphology retained from pristine MOF, brick, and rod shape at 600 • C (Figure 2d,e and Figure S3). The PXRD pattern of the NPC 800 sample showed two broad peaks of graphitic carbon at 23 (002) and 44 • (101) (Figure 2b) [7]. The absence of ZnO at higher carbonization temperature revealed when the temperature is close to its boiling point of ZnO (907 • C) is reduced to Zn and evaporate.
Furthermore, the SEM revealed the morphology partially retained the pristine MOF with distorted graphitic carbon structures (Figure 2f,g and Figure S4), TEM images noticeably show the presence of an abundant interconnected and oriented multilayer graphene domains can be observed (Figure 3a,b). Further, by increasing the temperature to 900 • C, the PXRD pattern indicated a mixture of graphite oxide (GO) and graphitic carbon.   Further, synthesized NPC materials were characterized by Raman spectroscopy for the degree of graphitization. The spectrum analyzed range between 1200 cm −1 to 1700 cm −1 bands were fitted with the spectra, 1180 cm −1 (A 1 band), 1340 cm −1 (D band), and 1600 cm −1 (G band) [42]. Figure S6 shows significantly broadened D and G bands. Gaussian fitting was used to separate the A 1 , D, G band and fitted after baseline subtraction. The I D /I G ratio increased while increasing the temperature, indicating the formation of disorder with a low degree of graphitization of NPC materials was obtained. The I D /I G ratio between D and G bands revealed the degree of graphitization in carbon-related materials. Temperature 500-700 • C carbonized materials obtained a higher degree of graphitization, due to the ZnO present in the carbon material. Because there is still a definite chemical interaction between ZnO and N atoms, the redshifts of the D bands by approximately 15 cm −1 to 1326 were observed [43]. Further, as we increased the temperature (800 and 900 • C), ZnO-N adducts were not detected and were also evidenced by PXRD. As the ratio is higher, it could be a low degree of graphitization, particularly those materials carbonized at ≥800 • C (see Table 1). The G band shifted to higher frequencies by approximately 6 cm −1 due to the nitrogen present in the NPC materials [44]. Chemical compositions of NPC were studied by ICP-MS and elemental analysis ( Figure S7). The zinc contents were investigated by ICP-MS, increasing carbonization temperature results the decreasing zinc percentage are 51.7% (600 • C), 43.72% (700 • C), 4.95% (800 • C), 0.26% (900 • C) and an appreciable amount of nitrogen (1.96-2.98 wt%) based on elemental analysis. Further, synthesized NPC materials were characterized by Raman spectroscopy for the degree of graphitization. The spectrum analyzed range between 1200 cm −1 to 1700 cm −1 bands were fitted with the spectra, 1180 cm −1 (A1 band), 1340 cm −1 (D band), and 1600 cm −1 (G band) [42]. Figure S6 shows significantly broadened D and G bands. Gaussian fitting was used to separate the A1, D, G band and fitted after baseline subtraction. The ID/IG ratio increased while increasing the temperature, indicating the formation of disorder with a low degree of graphitization of NPC materials was obtained. The ID/IG ratio between D and G bands revealed the degree of graphitization in carbonrelated materials. Temperature 500-700 °C carbonized materials obtained a higher degree of graphitization, due to the ZnO present in the carbon material. Because there is still a definite chemical interaction between ZnO and N atoms, the redshifts of the D bands by approximately 15 cm −1 to ≅1326 were observed [43]. Further, as we increased the temperature (800 and 900 °C), ZnO-N adducts were not detected and were also evidenced by PXRD. As the ratio is higher, it could be a low degree of graphitization, particularly those materials carbonized at ≥800 °C (see Table 1). The G band shifted to higher frequencies by approximately 6 cm −1 due to the nitrogen present in the NPC materials [44]. Chemical compositions of NPC were studied by ICP-MS and elemental analysis ( Figure S7). The zinc contents were investigated by ICP-MS, increasing carbonization temperature results the decreasing zinc percentage are 51.7% (600 °C), 43.72% (700 °C), 4.95% (800 °C), 0.26% (900 °C) and an appreciable amount of nitrogen (1.96-2.98 wt%) based on elemental analysis.   a S BET surface area was examined in the P/P 0 range of 0.01 to 0.1, which gave the best linearity. b Total pore volume at P/P 0 = 0.99. c Micropore volume (≤ 2 nm) and the values in asides are the percentage of the micropore volume relative to the total pore volume (V micro /V total ). d CO 2 uptake at 273 K and 1 bar and the values in asides are weight percentage (wt%).

Porous Property and CO 2 Uptake of NPC Materials
The textural properties of these NPC materials were evaluated by the N 2 sorption analyzer. The Figure 4a-c represented the N 2 uptake isotherm and corresponding pore sizes of the NPC materials. Table 1 represents the NPC material's surface area, pore volume and pore size. The N 2 sorption curves of the NPC materials possess type-I isotherms that steeply climb in the low-pressure range (P/P 0 = 0−0.10), suggesting that micropores were dominant [45]. In the high-pressure range (P/P 0 = 0.40−1.00), there were decent increases in the adsorption in all samples and a slight hysteresis loop between the sorption curves, which revealed that mesopores were also present in the materials. The surface area and total pore volume of the NPC 500-700 materials is nearly equal to 273, 287, 289, 296 m 2 /g and 0.18, 0.20, 0.22, 0.22 cm 3 /g correspondingly (see Table 1). Table 1 represents the NPC material's surface area, pore volume and pore size. The N2 sorption curves of the NPC materials possess type-I isotherms that steeply climb in the low-pressure range (P/P0 = 0−0.10), suggesting that micropores were dominant [45]. In the high-pressure range (P/P0 = 0.40−1.00), there were decent increases in the adsorption in all samples and a slight hysteresis loop between the sorption curves, which revealed that mesopores were also present in the materials. The surface area and total pore volume of the NPC500-700 materials is nearly equal to 273, 287, 289, 296 m 2 /g and 0.18, 0.20, 0.22, 0.22 cm 3 /g correspondingly (see Table 1). Whereas the BET surface area of the NPC800 material has 1192 m 2 /g and a total pore volume 0.92 cm 3 /g. The majority of the pores of NPC500-800 materials are 0.75, 1.4 nm retained from the pristine MOF (Figure 4c), while there are mesopores around 2.1-3 nm, which specifies the occurrence of mesopores in the NPC materials ( Figures S8-S13). While the NPC900 materials show a lesser surface area (303 m 2 /g), pore volume (0.45 cm 3 /g) indicates framework shrinkage and fragmentation throughout the high-temperature carbonization process. The total pore volume of NPC800 material has a better percentage than the NPC500-700 and NPC900 materials. It is noted that the NPC800 material Whereas the BET surface area of the NPC 800 material has 1192 m 2 /g and a total pore volume 0.92 cm 3 /g. The majority of the pores of NPC 500-800 materials are 0.75, 1.4 nm retained from the pristine MOF (Figure 4c), while there are mesopores around 2.1-3 nm, which specifies the occurrence of mesopores in the NPC materials ( Figures S8-S13). While the NPC 900 materials show a lesser surface area (303 m 2 /g), pore volume (0.45 cm 3 /g) indicates framework shrinkage and fragmentation throughout the high-temperature carbonization process. The total pore volume of NPC 800 material has a better percentage than the NPC 500-700 and NPC 900 materials. It is noted that the NPC 800 material reached 42% of micropores, whereas, the percentage of V micro /V total decreased significantly to 13% in the NPC 900 sample. CO 2 sorption is investigated for the NPC materials at 273 K at 1 bar (Figure 4d). NPC 800 demonstrated a higher CO 2 capture of 4.71 mmol/g than NPC 500 (2.85 mmol/g), NPC 550 (1.20 mmol/g), NPC 600 (1.24 mmol/g), NPC 700 (1.71 mmol/g) and NPC 900 (2.51 mmol/g) at 273 K and 1 bar. Such a micro-mesoporous structure of NPC 800 material provides a fast diffusion of CO 2 into the inner pores material. NPC 800 material showed CO 2 capacity value closely matches/ greater than those of the carbon-related materials (see Table S1).

Comparisons Voltammetric Behavior of Various SPCE/NPC Modified Electrode in FeCN
CV analysis was executed to study the electrochemical behavior of SPCE and SPCE/NPC T modified electrodes in 5 mM FeCN under a potential window from -0.2 to +0.6 V. As can be seen in Figure 5, bare SPCE exhibit a well-defined reversible redox peak at E • = +193 mV with a peak to peak potential difference (∆Ep = Epa − Epc) value of 126 mV, which is the characteristic peak for Fe 2+ /Fe 3+ interconversion [46,47]. After SPCE/NPC T modification, relatively higher/lower redox current responses were noticed with a ∆Ep value of about 561, 235, 125, 112, 137 and 140 mV, while the relative current change (∆Ia) was recorded for SPCE/NPC 500 , SPCE/NPC 550 , SPCE/NPC 600 , SPCE/NPC 700 , SPCE/NPC 800 , SPCE/NPC 900 of about −99, −88, −29, −12, +83 and +113 µA, respectively. The observation is due to the semiconductor Zn moieties existing up to a carbonization temperature of 700 • C that results in a decrease in FeCN signal. In contrary, carbonization at 800 and 900 • C produced relatively smaller Zn moieties with NPC and hence an increase in signal. This result suggests that the semiconductor Zn content decreased with increasing carbonization temperature. In other words, the FeCN current response is inversely proportional to the Zn content. The obtained results coincide with the elemental analysis, ICP-MS and PXRD results. modified electrodes in 5 mM FeCN under a potential window from -0.2 to +0.6 V. As can be seen in Figure 5, bare SPCE exhibit a well-defined reversible redox peak at E° = +193 mV with a peak to peak potential difference (ΔEp = Epa-Epc) value of 126 mV, which is the characteristic peak for Fe 2+ /Fe 3+ interconversion [46,47]. After SPCE/NPCT modification, relatively higher/lower redox current responses were noticed with a ΔEp value of about 561, 235, 125, 112, 137 and 140 mV, while the relative current change (ΔIa) was recorded for SPCE/NPC500, SPCE/NPC550, SPCE/NPC600, SPCE/NPC700, SPCE/NPC800, SPCE/NPC900 of about −99, −88, −29, −12, +83 and +113 µA, respectively. The observation is due to the semiconductor Zn moieties existing up to a carbonization temperature of 700 °C that results in a decrease in FeCN signal. In contrary, carbonization at 800 and 900 °C produced relatively smaller Zn moieties with NPC and hence an increase in signal. This result suggests that the semiconductor Zn content decreased with increasing carbonization temperature. In other words, the FeCN current response is inversely proportional to the Zn content. The obtained results coincide with the elemental analysis, ICP-MS and PXRD results.

Detection of H2O2 at SPCE/NPCT
The surface area and porous defective sites have an important role in the electrochemical sensors. Therefore, H2O2 sensing applicability was tested for SPCE/NPC500, SPCE/NPC550, SPCE/NPC600, SPCE/NPC700, SPCE/NPC800, SPCE/NPC900, respectively. Figure 6 shows electro catalytic reduction CVs of H2O2 at various SPCE/NPCT electrodes. CV measurements were done in 0.1 M, pH 7.4 PB solution under the potential sweeping from 0 to −1.2 V at a scan rate of 100 mV s −1 . During the cathodic segment, H2O2 reduction peak [48] was noticed at ~−0.7 V for SPCE and for SPCE/NPCT the same reduction peak was noticed with lower over potential (~−0.4 V). Among the various electrodes, detection response are clearer and more explicit at SPCE/NPC600. These results

Detection of H 2 O 2 at SPCE/NPC T
The surface area and porous defective sites have an important role in the electrochemical sensors. Therefore, H 2 O 2 sensing applicability was tested for SPCE/NPC 500 , SPCE/NPC 550 , SPCE/NPC 600 , SPCE/NPC 700 , SPCE/NPC 800 , SPCE/NPC 900 , respectively. Figure 6 shows electro catalytic reduction CVs of H 2 O 2 at various SPCE/NPC T electrodes. CV measurements were done in 0.1 M, pH 7.4 PB solution under the potential sweeping from 0 to −1.2 V at a scan rate of 100 mV s −1 . During the cathodic segment, H 2 O 2 reduction peak [48] was noticed at~−0.7 V for SPCE and for SPCE/NPC T the same reduction peak was noticed with lower over potential (~−0.4 V). Among the various electrodes, detection response are clearer and more explicit at SPCE/NPC 600 . These results evidently exposed that the SPCE/NPC600 electrode exhibited better electrocatalytic H 2 O 2 reduction than other electrodes. Therefore, SPCE/NPC 600 was chosen for further studies.
Materials 2019, 12, x FOR PEER REVIEW 9 of 13 evidently exposed that the SPCE/NPC600 electrode exhibited better electrocatalytic H2O2 reduction than other electrodes. Therefore, SPCE/NPC600 was chosen for further studies.

Flow Injection Analysis (FIA) Detection of H2O2 at SPCE/NPC600
The above observation was further utilized for amperometric FIA analysis of H2O2. The H2O2 reduction current increased linearly with increasing concentration, in which H2O2 was electrochemically reduced at −0.4 V by applying a potential, and thus yielded quantitative current responses corresponding to the content of H2O2 (Figure 7). A wide linearity range between 100 µM and 10 mM with a R 2 value of 0.9865 and a limit of detection (LOD) 27.5 µM were obtained. In order to access the repeatability of a SPCE/NPC600 modified electrode, 12 repeated injections of 0.5 mM H2O2 were performed and a RSD value of 4.13% was obtained. Compared to a few other Zn based H2O2 sensors (Table S2), the present method exhibited a wide linear range along with a specific sensitivity of 108.7 µA mM −1 cm −2 .

Flow Injection Analysis (FIA) Detection of H 2 O 2 at SPCE/NPC 600
The above observation was further utilized for amperometric FIA analysis of H 2 O 2 . The H 2 O 2 reduction current increased linearly with increasing concentration, in which H 2 O 2 was electrochemically reduced at −0.4 V by applying a potential, and thus yielded quantitative current responses corresponding to the content of H 2 O 2 (Figure 7). A wide linearity range between 100 µM and 10 mM with a R 2 value of 0.9865 and a limit of detection (LOD) 27.5 µM were obtained. In order to access the repeatability of a SPCE/NPC 600 modified electrode, 12 repeated injections of 0.5 mM H 2 O 2 were performed and a RSD value of 4.13% was obtained. Compared to a few other Zn based H 2 O 2 sensors (Table S2)

Conclusions
Herein, we reported the synthesized NPC materials at various carbonization temperatures at a constant time under a N2 atmosphere. NPC materials surface, morphology, chemical composition, porous properties where characterized by PXRD, SEM, TEM, Raman spectroscopy, ICP-MS, elemental analysis, and 77 K N2 sorption isotherms. Pristine MOF pore size was tuned to the porous carbon material, such an ultramicropore, micropore and mesopore combined in unique material and interaction between ZnO to NPC to give the pathway to synthesize the effective electrochemical property and CO2 sorption materials. These combinations in NPC800 exhibited a higher CO2 uptake of 4.71 mmol g −1 compare to other NPCT materials. NPC600 displayed a good electrochemical reduction towards H2O2. Under optimal conditions, our sensor exhibited linearity that ranged from 0.1-10 mM, which confirmed its sensitive response to H2O2 over a wide range of concentrations. The detection limit was determined to be 27.5 µM (S/N = 3) Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, Figure S1. SEM image of (a) NPC500 and (b) NPC550. Figure S2. SEM image of NPC700 (a,b). Figure S3. SEM images of NPC600 (a-d). Figure  S4. SEM image of NPC800 (a-d). Figure S5. SEM image of NPC900 (a-d). Figure S6. Raman spectra of the obtained NPC materails. (a) NPC500, (b) NPC550, (c) NPC600, (d) NPC700, (e) NPC800 and (f) NPC900. Figure S7. Relative atom percentage at different carbonization temperature (600-900 °C). Figure S8. NLDFT pore size distribution profile for NPC500. Figure S9. NLDFT pore size distribution profile for NPC550. Figure S10. NLDFT pore size distribution profile for NPC600. Figure S11. NLDFT pore size distribution profile for NPC700. Figure S12. NLDFT pore size distribution profile for NPC800. Figure S13. NLDFT pore size distribution profile for NPC900. Table S1. Comparison of CO2 uptake with previously reported carbon related materials and MOF-derived carbon materials at temperature 273K in 1 bar. Table S2. Comparison of Zn electrode-based H2O2 sensors with previously reported ZnO/carbon related materials.

Conclusions
Herein, we reported the synthesized NPC materials at various carbonization temperatures at a constant time under a N 2 atmosphere. NPC materials surface, morphology, chemical composition, porous properties where characterized by PXRD, SEM, TEM, Raman spectroscopy, ICP-MS, elemental analysis, and 77 K N 2 sorption isotherms. Pristine MOF pore size was tuned to the porous carbon material, such an ultramicropore, micropore and mesopore combined in unique material and interaction between ZnO to NPC to give the pathway to synthesize the effective electrochemical property and CO 2 sorption materials. These combinations in NPC 800 exhibited a higher CO 2 uptake of 4.71 mmol g −1 compare to other NPC T materials. NPC 600 displayed a good electrochemical reduction towards H 2 O 2 . Under optimal conditions, our sensor exhibited linearity that ranged from 0.1-10 mM, which confirmed its sensitive response to H 2 O 2 over a wide range of concentrations. The detection limit was determined to be 27.5 µM (S/N = 3) Supplementary Materials: The following are available online at http://www.mdpi.com/1996-1944/13/2/264/s1, Figure S1. SEM image of (a) NPC 500 and (b) NPC 550 . Figure S2. SEM image of NPC 700 (a,b). Figure S3. SEM images of NPC 600 (a-d). Figure S4. SEM image of NPC 800 (a-d). Figure S5. SEM image of NPC 900 (a-d). Figure  S6. Raman spectra of the obtained NPC materails. (a) NPC 500 , (b) NPC 550 , (c) NPC 600 , (d) NPC 700 , (e) NPC 800 and (f) NPC 900 . Figure S7. Relative atom percentage at different carbonization temperature (600-900 • C). Figure S8. NLDFT pore size distribution profile for NPC 500 . Figure S9. NLDFT pore size distribution profile for NPC 550 . Figure S10. NLDFT pore size distribution profile for NPC 600 . Figure S11. NLDFT pore size distribution profile for NPC 700 . Figure S12. NLDFT pore size distribution profile for NPC 800 . Figure S13. NLDFT pore size distribution profile for NPC 900 . Table S1. Comparison of CO 2 uptake with previously reported carbon related materials and MOF-derived carbon materials at temperature 273K in 1 bar. Table S2. Comparison of Zn electrode-based H 2 O 2 sensors with previously reported ZnO/carbon related materials.