Supporting Information

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1 Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, Supporting Information for Adv. Mater., DOI: /adma Metal-Organic Frameworks Reactivate Deceased Diatoms to be Efficient CO2 Absorbents Dingxin Liu, Jiajun Gu, Qinglei Liu, Yongwen Tan, Zhuo Li, Wang Zhang, Yishi Su, Wuxia Li, Ajuan Cui, Changzhi Gu, and Di Zhang*

2 Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, Supporting Information for Adv. Mater., DOI: /adma Metal-Organic Frameworks Reactivate Deceased Diatoms to be Efficient CO 2 Absorbents Dingxin Liu, Jiajun Gu,* Qinglei Liu, Yongwen Tan, Zhuo Li, Wang Zhang, Yishi Su, Wuxia Li, Ajuan Cui, Changzhi Gu, and Di Zhang* Contents 1. Experimental details (Scheme S1) 2. Low-magnification SEM image, XRD, and TGA results of Z8/D (Figure S1) 3. Analyses on ZIF-8 content in Z8/D (Table S1) 4. N 2 (77 K) and Ar (88 K) uptake isotherms on Z8/D, ZIF-8, and diatomite (Figure S2) 5. FTIR and elemental analyses on Z8/D powders ground in liquid N 2 against time (Figure S3, Table S2) 6. C 2 H 2 uptake isotherms (293 K and 273K) on Z8/D, ZIF-8, and diatomite (Figure S4) 7. XRD, NMR, and CO 2 uptake studies on M5/D (Figure S5) 8. Analyses on MOF-5 content in M5/D (Table S3) 9. XRD, NMR, and CO 2 uptake studies on Z8/SBA-15 (Figure S6) 10. Analyses on ZIF-8 content in Z8/SBA-15 (Table S4) 11. Adsorption bonus from combination (Figure S7, Tables S5-S7) 12. Layered structures in frustules of fresh diatoms without chemical treatments (Figure S8) 13. Gas adsorption and desorption data (Tables S8-S13) 1

3 1. Experimental details Fabrication of Z8/D Diatomite were purchased from Celite Co., Ltd., China, containing approximately 60% Coscinodiscus sp., 30% Cyclotella sp., and 5% Melosira sp.. General synthesis route to MOFs/D includes three steps: (1) a surface amination process of diatom frustules full of hydroxyls, (2) coordination of Zn 2+ on the surface of frustules, and (3) MOFs/diatomite formation via hydrothermal synthesis. [1] The diatomite (ca. 0.6 g) were first pretreated with HCl solution (37 %) for 5 h, rinsed in de-ionized water, and dried in the air. Then we used the ethylenediamine (purchased from Sinopharm Chemical Reagent Co., Ltd., China, 99.0%) to activate the diatomite (Scheme S1). The surface-activated diatomite were then soaked in water saturated with Zn(NO 3 ) 2 4H 2 O (2.61 g or mol, from Merck KGaA Darmstadt, Germany, 98.5%) for 5 h, rinsed in de-ionized water, and air-dried. After that, 2-methylimidazole (H-MeIM) (1.64 g or mol, from Aladdin Chemistry Co., Ltd., 98.0%) was dissolved in 40 ml dimethylformamide (DMF, from Shanghai Ling Feng Chemical Reagent Co., Ltd., China, 99.5%), and Zn 2+ coordinated diatomite were put into this solution, stirred at room temperature for 30 min. The mixture was then sealed in a chemical reactor, heated to 140 C (2 C min -1 ) in a programmable oven, held at this temperature for 24 h, and cooled down to room temperature at a rate of 0.4 C min -1. After the removal of mother liquor from the mixture, the rest of the mixture was rinsed using chloroform (30 ml, from Sinopharm Chemical Reagent Co., Ltd., China, 99.0%). We collected white powders (Z8/D) from the bottom layer, washed them three times with DMF (10 ml), and dried them in air for 10 min. Diatomite for gas adsorption analyses (except the measurements in Figure 3g in the main text where raw diatomite were used) were treated in the same way but without the Zn 2+ coordination process. ZIF-8 content was evaluated via Zn content using ICP-OES on an icap 6300 ICP spectrometer from Thermo Scientific, U. S. In addition, N present was measured using stable isotope ratio mass spectrometer on a Vario EL III/Isoprime from Elementar, Germany. Fabrication of Z8/SBA-15 SBA-15 was purchased from Nanjing XFNANO Materials Tech Co., Ltd, China. The silica frustules were replaced by the SBA-15 (amorphous silica) as substrates to generate composites with ZIF-8. The fabrication route to Z8/SBA-15 is the same as that to Z8/D. Fabrication of M5/D The surface functionalization process for fabricating M5/D is the same as that for Z8/D. The surface-activated diatomite were soaked in de-ionized water saturated with Zn(NO 3 ) 2 4H 2 O (1.57 g or mol, from Merck KGaA Darmstadt, Germany, 98.5%) for 5 h, rinsed in de-ionized water, and air-dried. Then, terephthalic acid (0.33 g or mol, from Ourchem Co., Ltd., 99.0%) was dissolved in 50 ml diethylformamide (DEF, from Sigma-Aldrich Co., Ltd., 99.0%), and the Zn 2+ coordinated diatomite was put into this solution, stirred at room temperature for 30 min. The mixture was then sealed in a chemical reactor, heated to 105 C (2 C min -1 ) in a programmable oven, held at this temperature for 24 h, and cooled down to room temperature at a rate of 0.4 C/min. After the removal of mother liquor from the 2

4 mixture, the rest of the mixture was rinsed using chloroform. The cubic crystals were stirred in chloroform (30 ml, from Sinopharm Chemical Reagent Co., Ltd., China, 99.0%) for 24 h to exchange the DEF. We collected white powders (M5/D) from the bottom layer, and dried them under vacuum at 105 C for 12 h. MOF-5 content was evaluated via Zn present using ICP-OES on an icap 6300 ICP spectrometer from Thermo Scientific, U. S. Characterization SEM analyses were conducted on an FEI Quanta 250 SEM (20 kv) equipped with an energy dispersive spectrometer (EDS, Oxford Instruments, 80 mm 2 detector). Samples were treated via Au sputtering before observation. HRTEM analyses were carried out using an FEI Tecnai-F20 (200 kv) and a JOEL 2010F (200 kv) instrument, respectively. 13 C CP/MAS NMR analyses were conducted on a Bruker Avance III 300 NMR spectrometer. Spectra were measured at a Larmor frequency of MHz, a MAS frequency of 10 khz and a sample temperature of 293 K. Micro-Raman spectra were recorded using a Renishaw invia micro-raman instrument (50 short focal length objective). A 785 nm output from an argon-ion laser was applied as the light source. Power at the sample surface was approximately 0.20 mw. Samples were examined using XRD on a D-max/2550 X-ray diffractometer system (Rigaku, 35 kv, 20 ma, Cu Kα,) at 2 º min -1. Thermo gravimetric analysis (TGA) was conducted on a STA PT1600 thermal gravimetric analyzer (Linseis German) with samples in a continuously flowing nitrogen atmosphere. Samples were heated at a constant rate of 2 C min -1 during measurements. Fourier transform infrared spectroscopy (FTIR) spectra were collected on a Nicolet 6700 instrument (32 integrals) from Thermo Fisher Scientific, U. S. Particle size of as-ground Z8/D powders was measured on a laser particle size analyzer (Zetasizer Nano ZS) from Malvern Instruments Ltd, U. K. TEM specimen preparation by focused-ion-beam Focused-ion-beam (FIB) processing was conducted on an FEI Helios NanoLab TM 600i Dual-Beam system. The ion column features a singly charged liquid gallium ion source, and it is placed at an angle of 52 to the vertically oriented electron beam column. To fix the frustules on the edge of a half TEM copper gird, a platinum composite stripe was first grown by FIB induced deposition using a 1 pa ion beam current with (CH 3 ) 3 Pt (CpCH 3 ) as the gas precursor. For micro-stripe deposition, the gas precursor molecules were introduced to the area through a gas nozzle. The chamber pressure was about mbar during deposition. For FIB milling, 30 kv Ga ions with a beam current of 80 pa was first applied to reduce the size of the target. 30 kv Ga ions with a beam current of 7 pa was then used for rough polishing. Finally, 2 kv Ga ions with a beam current of 5 pa was used for fine polishing (3-6 times). The frustules slice for TEM observation is about 80 nm in thickness. The advantages of using such a system is that SEM can be used for imaging to avoid unnecessary ion scanning of the frustules, and low voltage ions can minimize the potential damages caused by the energetic ions. It has been confirmed that utilizing such a facility, polishing with a 2 kv ion beam could reduce the damage to be less than 2 nm from the surface. Measurement of gas isotherms CO 2 uptake was measured out on an IGA 002 gravimetric analyzer (Hiden Isochema, U. K.). Samples were 3

5 analyzed in a temperature-controlled water bath. Before measurement, all samples excepting M5/D (degassed at 80 ºC) were degassed under vacuum conditions (<10-5 mbar) at 105 ºC for 6 h (heating rate: 10 ºC min -1, outgas rate: 50 mbar min -1 ). At the targeted adsorption temperature (25 ºC or 10 ºC), controlled amounts of CO 2 were added to the sample chamber for adsorption. The changes in weight of the loaded sample were continuously recorded throughout the adsorption process until equilibrium was reached. N 2, Ar, and C 2 H 2 isotherms were recorded on an ASAP 2020 accelerated surface area and porosimetry system (volumetric adsorption analyzer, Micromeritics, U. S.). BET surface area was calculated using the data within the relative pressure range of 0.05 to All samples were degassed in vacuum at 105 ºC for 6 h prior before measurement. Scheme S1. Synthesis route toward various MOFs/SiO 2. a) Original silica substrate. b) Surface amination process. c) Coordination of Zn 2+ on the silica surface. d) Formation of Z8/SiO 2. e) Formation of M5/SiO 2. 4

6 2. Low-magnification SEM image, XRD, and TGA results of Z8/D Figure S1. a) Low-magnification SEM image of Z8/D. Approximately 90% of the diatomite used in this work were of centric diatoms. b) XRD results of ZIF-8, Z8/D, and diatomite powders. The ZIF-8 nanoparticles loaded on diatomite are ca. 30 nm in size (calculated using Debye-Scherer formula). c) TGA trace of Z8/D. The slight weight-loss (1.8% till 450 C) could be attributed to the escape of guest molecules in ZIF-8.[1] 5

7 3. Analyses on ZIF-8 content in Z8/D Table S1. Analyses on ZIF-8 content in Z8/D. batch Zn content [a] N content [b] Zn/N ratio content of ZIF-8 [d] content of frustules ± ± ± ± ± ± ± ± ± ± average / / 1.24±0.15 [c] 57.2± ±4.4 diatomite 0.00 / / / / [a] Four samples were measured in one batch. [b] Six samples were measured in one batch. [c] Its stoichiometric ratio in ZIF-8 is [d] Calculated from Zn present. 6

8 4. N 2 (77 K) and Ar (88 K) uptake isotherms on Z8/D, ZIF-8, and diatomite Figure S2. Surface area (SA) analyses on Z8/D. a) N 2 uptake at 77 K; b) Ar uptake at 87 K; c) SA of Z8/D, ZIF-8, and diatomite under 1 bar. The SA of Z8/D is smaller than that of the commercial ZIF-8. Since no significant byproducts were detected in Z8/D (Figure 1 and Figure S1), the observed 6 7 times decrease instead of 2 times decrease in SA for Z8/D against commercial ZIF-8 might be caused by the in situ formation of ZIF-8 nano-particles on the diatomite surfaces. Such a combination process would produce lots of three-dimensionally distributed interfaces that could block some open molecular apertures of ZIF-8 and thus affect the kinetic process for molecules with larger kinetic diameters (3.5 Å for Ar and 3.6 Å for N 2 ) [2] to enter the ZIF-8 cages, giving rise to the decrease in surface area measured with these two gases. For CO 2 molecules with kinetic diameters (3.3 Å) smaller than the size of ZIF-8 apertures (3.4 Å), this effect was not significant. More detailed kinetic analyses are underway at present. 7

9 5. FTIR and elemental analyses on Z8/D powders ground in liquid N 2 against time Figure S3. FTIR analyses on Z8/D powders ground in liquid N 2 against time. The arrow at 800 cm -1 denotes the symmetric stretching mode of Si-O-Si. Rest peaks are from ZIF-8. [1] Results show that the functional groups were well-kept through the mechanical grinding. Table S2. ICP analyses on Z8/D powders ground in liquid N 2 against time. grinding time Zn content [a] content of ZIF-8 [b] content of frustules 0 min 13.51± min 13.25± min 13.12± min 12.96± min 12.88± average / 56.8± ±1.1 diatomite 0.00 / / [a] Four samples were measured in one batch. [b] Calculated from Zn present. 8

10 6. C 2 H 2 uptake isotherms (293 K and 273K) on Z8/D, ZIF-8, and diatomite Figure S4. C 2 H 2 uptake isotherms (293 K and 273K) on Z8/D, ZIF-8, and diatomite. 9

11 7. XRD, NMR, and CO 2 uptake studies on M5/D Figure S5. a) XRD results of M5/D. b) 13 C CP/MAS NMR spectrum of M5/D, showing no significant byproducts in the samples. c) CO 2 uptake isotherms on M5/D powders (blue curves) and on M5/D powders ground in liquid N 2 for 15 min (amber curves). Like for Z8/D, the CO 2 uptake amount decreases for M5/D after the grinding process. 10

12 8. Analyses on MOF-5 content in M5/D Table S3. ICP analyses on MOF-5 content in M5/D. batch Zn content [a] content of MOF-5 [b] wt % content of frustules wt % ± ± average / 33.9± ±1.1 diatomite 0.00 / / [a] Four samples were measured in one batch. [b] Calculated from Zn present. 9. XRD, NMR, and CO 2 uptake studies on Z8/SBA-15 Figure S6. a) XRD and b) 13 C CP/MAS NMR spectrum of Z8/SBA-15. c) CO 2 uptake isotherms on Z8/SBA-15 (amorphous silica). 11

13 10. Analyses on ZIF-8 content in Z8/SBA-15 Table S4. Analyses on ZIF-8 content in Z8/SBA-15. batch Zn content [a] N content [b] Zn/N ratio content of ZIF-8 [d] content of SBA ± ± ± ± average / / 1.14±0.01 [c] 61.7± ±0.5 diatomite 0.00 / / / / [a] Four samples were measured in one batch. [b] Six samples were measured in one batch. [c] Its stoichiometric ratio in ZIF-8 is [d] Calculated from Zn present. 11. Adsorption bonus from combination Figure S7. CO 2 uptake isotherms (283 K) on Z8/D powders. 12

14 Table S5. Additional gas uptake relative to pure ZIF-8 by diatom frustules (SiO 2 ) in 1 g Z8/D. probe T uptake on uptake on absorbed absorbed solid-state solid-state Z8/D pure ZIF-8 by ZIF-8 by SiO 2 density of volume of in Z8/D in Z8/D adsorbate adsorbate [K] [mmol] [mmol g -1 ] [mmol] [mmol] [mmol cm -3 ] [mm 3 ] CO (27.80) [a] (22.73) C 2 H (20.32) (17.50) [a] Data between the parentheses are the solid-state volumes of the adsorbates in 1 g diatomite. Table S6. Additional CO 2 uptake relative to pure MOF-5 by diatom frustules (SiO 2 ) in 1 g M5/D. T uptake on uptake on absorbed by absorbed by solid-state solid-state M5/D pure MOF-5 MOF-5 SiO 2 density of volume of in M5/D in M5/D adsorbate adsorbate K [mmol] [mmol g -1 ] [mmol] mmol [mmol cm -3 ] [mm 3 ] [a][3] (26.59) [b] [a] Directly measured from published figures in Ref. 3. [b] Datum between the parentheses is the solid-state volume of CO 2 in 1 g diatomite. Table S7. Additional CO 2 uptake relative to pure ZIF-8 by SBA-15 (SiO 2 ) in 1 g Z8/SBA-15. T uptake on uptake on absorbed by uptake on absorbed by additional solid-state solid-state Z8/SBA-15 pure ZIF-8 ZIF-8 in pure SBA-15 in adsorption density of volume of Z8/SBA-15 SBA-15 Z8/SBA-15 CO 2 CO 2 [K] [mmol] [mmol g -1 ] [mmol] [mmol g -1 ] [mmol] [mmol] [mmol cm -3 ] mm (5.90) [a] [a] Datum between the parentheses is the solid-state volume of CO 2 in 1 g silica. 13

15 12. Layered structures in frustules of fresh diatoms without chemical treatments Figure S8. a) TEM image of the frustules of fresh diatoms (Coscinodiscus sp.) without any chemical treatments. b) Thin area obtained via FIB. c) and d) Close-up observations of the areas denoted by the arrows in (b). e) Higher magnification image of (d) shows the layered structure. Scale bars: a) 1 μm; b) 200 nm; c) and d) 50 nm; e) 20 nm. Detailed analyses are beyond the scope of this communication and will be published elsewhere. 14

16 13. Gas adsorption/desorption data Table S8. Average CO 2 uptake on Z8/D at 298 K. pressure adsorption pressure desorption [mbar] [mmol g -1 ] [mbar] [mmol g -1 ]

17 Table S9. Average N 2 uptake on Z8/D at 77 K. p/p 0 adsorption [cm 3 g -1 ] p/p 0 desorption [cm 3 g -1 ]

18 Table S10. Average Ar uptake on Z8/D at 87 K. p/p 0 adsorption [cm 3 g -1 ] p/p 0 desorption [cm 3 g -1 ]

19 Table S11. Average C 2 H 2 uptake on Z8/D at 293 K. pressure adsorption [a] pressure desorption [a] [mmhg] [mmol g -1 ] [mmhg] [mmol g -1 ]

20 [a] Directly generated by the software ASAP-2020 v 3.01 equipped on the ASAP-2020, Micromeritics. Table S12. Average CO 2 uptake on M5/D at 298 K. pressure adsorption pressure desorption [bar] [mmol g -1 ] [bar] [mmol g -1 ]

21 Table S13. Average CO 2 uptake on Z8/SBA-15 at 298 K. pressure adsorption pressure desorption [bar] [mmol g -1 ] [bar] [mmol g -1 ] References [1] K. S. Park, et al., Proc. Natl. Acad. Sci. U.S.A. 2006, 103, [2] J. R. Li, et al., Chem. Soc. Rev. 2009, 38, [3] H. X. Deng, et al., Science 2010, 327,