Hydrogen storage in metal organic framword mil 88s a computational study = nghiên cứu lưu trữ khí hydro sử dụng vật liệu khung hữu cơ kim loại mil 88s bằng phương pháp mô phỏng

VIETNAM NATIONAL UNIVERSITY HO CHI MINH CITY HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY Nguyen Thi Xuan Huynh HYDROGEN STORAGE IN METAL-ORGANIC FRAMEWORK MIL-88S: A COMPUTATIONAL STUDY A dissertation submitted for the degree of Doctor of Philosophy Ho Chi Minh City – 2019 VIETNAM NATIONAL UNIVERSITY HO CHI MINH CITY HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY Nguyen Thi Xuan Huynh HYDROGEN STORAGE IN METAL-ORGANIC FRAMEWORK MIL-88S: A COMPUTATIONAL STUDY Major: ENGINEERING PHYSICS Major code: 62520401 Independent Reviewer 1: Assoc Prof Dr Pham Tran Nguyen Nguyen Independent Reviewer 2: Assoc Prof Dr Nguyen Thanh Tien Reviewer 1: Assoc Prof Dr Phan Bach Thang Reviewer 2: Assoc Prof Dr Huynh Quang Linh Reviewer 3: Dr Phan Hong Khiem SCIENTIFIC SUPERVISORS: Dr Do Ngoc Son Dr Pham Ho My Phuong DECLARATION I declare that this doctoral dissertation was written by myself, that the work contained herein is my own except where explicitly stated otherwise in the text, and that this work has not been submitted for any other degrees or professional qualification except as specified Parts of this dissertation were published in the following papers: [1] T T T Huong, P N Thanh, N T X Huynh, and D N Son, “Metal-Organic Frameworks: State-of-the-art Material for Gas Capture and Storage,” VNU Journal of Science: Mathematics – Physics, vol 32, pp 67-84, 2016 [2] N T X Huynh, O M Na, C Viorel, and D.N Son, “A computational approach towards understanding hydrogen gas adsorption in Co-MIL-88A,” RSC Advances, vol 17, pp 39583-39593, 2017 [3] N T X Huynh, C Viorel, and D.N Son, “Hydrogen storage in MIL-88 series,” Journal of Materials Science, vol 54, pp 3994-4010, 2019 Author of dissertation Nguyen Thi Xuan Huynh i ABSTRACT Fossil fuel-based energy consumption causes serious environmental impacts such as air pollution, greenhouse effect, and so on Therefore, searching clean and renewable energy sources is urgent to meet the demand for sustainable development of the global society and economy Hydrogen gas (H2) is a reproducible, clean, and pollution-free energy carrier for both transportation and stationary applications Hydrogen gas has a much higher energy density than other fuels; and thus, it becomes one of the most promising candidates to replace petroleum Therefore, in recent years, the interest in the research and development of hydrogen energy has grown constantly A safe, efficient, and commercial solution for hydrogen storage is based on adsorption in porous materials, which have the exceptionally large surface area and ultrahigh porosity such as metal-organic framework (MOF) materials In order to be selected as porous materials for gas storage, MOFs must be stable to avoid collapsed under humid conditions MIL-88 series (abbreviated as MIL-88s including MIL-88A, MIL-88B, MIL-88C and MIL-88D) is highly stable and flexible sorbents For these reasons, MIL-88s becomes a suitable candidate for the storage of hydrogen gas based on the physisorption Moreover, coordinatively unsaturated metal centers in MIL-88s are able to enhance gas uptakes significantly at ambient temperatures and low pressures These materials have been investigated and highly evaluated for various applications such as gas storage/capture and separation of binary gas mixtures in recent years; however, they have not yet been evaluated for hydrogen storage These outstanding features have attracted my attention to consider the hydrogen storage capacity in MIL-88 series In this dissertation, the van der Waals dispersion-corrected density functional theory (vdW-DF) calculations were used to examine the stable adsorption sites of the hydrogen molecule in MIL-88s and clarify the interaction between H2 and MIL-88s via electronic structure properties This observation showed an implicit role of electronic structures on the H2 adsorption capacity at the considered temperature and pressure conditions Besides, it was found that the H2@MIL-88s interaction is dominated by the bonding state () of the hydrogen molecule and the p orbitals of the ii O and C atoms in MIL-88s For MIL-88A and B, the d orbitals of the metals also play an important role in the interaction with H2 Moreover, grand canonical Monte Carlo (GCMC) simulations were used to compute hydrogen uptakes in MIL-88s at the temperatures of 77 K and 298 K and the pressures up to 100 bar For Fe based-MIL-88 series, we found that MIL-88D is very promising for the gravimetric hydrogen storage (absolute/excess uptakes = 5.15/4.03 wt% at 77 K and 0.69/0.23 wt% at 298 K), but MIL-88A is the best alternative for the absolute/excess volumetric hydrogen storage with 50.69/44.32 g/L at 77 K and 6.97/2.49 g/L at 298 K Via this research, scandium (Sc) was also found as the best transition metal element for the replacement of Fe in MIL-88A for the hydrogen storage, in which absolute/excess uptakes are 5.30/4.63 wt% at 77 K and 0.72/0.29 wt% at 298 K for gravimetric uptakes; 51.99/45.51 g/L at 77 K and 7.08/2.83 g/L at 298 K for volumetric uptakes The hydrogen storage capacity is the decrease in the order: Sc-, Ti-, V-, Cr-, Mn-, Fe-, and Co-MIL-88A The calculations showed that the results are comparable to the best MOFs for the hydrogen storage up to date The results also elucidated that the gravimetric hydrogen uptakes depend on the specific surface area and pore volume of the MIL-88s These important structural features, if properly improved, lead to an increase in the capability of hydrogen storage in MIL-88s iii TÓM TẮT LUẬN ÁN Tiêu thụ lượng dựa nguồn nhiên liệu hóa thạch ngày ảnh hưởng nghiêm trọng đến môi trường gây ô nhiễm khơng khí, hiệu ứng nhà kính Do đó, để đáp ứng nhu cầu phát triển bền vững cho đời sống xã hội kinh tế toàn cầu, việc tìm kiếm nguồn lượng tái tạo vấn đề cấp thiết Như biết, hydro nguồn khí phong phú đáp ứng cho nhu cầu lượng sạch, tái tạo không gây ô nhiễm môi trường cho ứng dụng di chuyển chỗ Hydro lại có mật độ lượng cao nhiều so với nhiên liệu khác nên chọn ứng viên sáng giá cho việc thay xăng dầu Với đặc tính nên quan tâm đến nghiên cứu phát triển lượng hydro tăng lên không ngừng năm gần Một giải pháp đảm bảo tính an tồn, hiệu kinh tế cho lưu trữ hydro hấp phụ khí vào vật liệu xốp Những vật liệu xốp đánh giá cao cho khả lưu trữ khí hydro vật liệu xốp có diện tích bề mặt lớn tính xốp cực cao họ vật liệu khung hữu kim loại (MOF) Để chọn làm vật liệu lưu trữ khí, vật liệu MOF phải có tính ổn định bền để tránh tượng phá vỡ cấu trúc môi trường ẩm Chuỗi MIL-88A, MIL-88B, MIL-88C MIL-88D (viết tắt MIL-88s) đáp ứng yêu cầu chuỗi vật liệu có cấu trúc linh hoạt bền môi trường ẩm Do đó, chuỗi MIL-88s dự đốn ứng viên sáng giá cho lưu trữ hydro dựa tính chất hấp phụ Hơn nữa, MIL-88s chứa tâm kim loại chưa bão hịa mà đặc tính cho giải pháp chiến lược tăng cường đáng kể lượng khí hấp phụ vào MOF điều kiện nhiệt độ phòng áp suất thấp Trong thời gian gần đây, chuỗi MIL-88s nghiên cứu đánh giá cao cho nhiều ứng dụng lưu trữ, bắt giữ tách khí; nhiên, chúng chưa đánh giá cho khả lưu trữ hydro phương pháp thực nghiệm tính tốn Với tính bật trên, phương pháp tính tốn sử dụng để xem xét khả lưu trữ hydro MIL-88s giải thích chi tiết tương tác trạng thái điện tử phân tử H2 với nguyên tử MIL-88s Trong luận án này, phương pháp lý thuyết phiếm hàm mật độ (DFT) có hiệu chỉnh van der Waals (vdW-DF) sử dụng để tính lượng liên kết hay iv lượng hấp phụ từ tìm vị trí hấp phụ bền cho H2 chuỗi MIL-88s Cụ thể hơn, dựa tính chất cấu trúc điện tử, tương tác H2 MIL-88s làm sáng tỏ Kết tính tốn vị trí hấp phụ bền H cấu trúc MIL-88s Kết tương tác H2 MIL-88s đóng góp trạng thái liên kết ( - trạng thái bonding) phân tử H2 tương tác với quỹ đạo p nguyên tử O C MIL-88s Đối với MIL-88A B, tính tốn vdW-DF quỹ đạo d kim loại đóng vai trị quan trọng tương tác với H2 Bên cạnh đó, để đánh giá định lượng khả lưu trữ hydro MIL-88s nhiệt độ 77 K 298 K với áp suất lên đến 100 bar, phương pháp mơ Monte Carlo tắc lớn (GCMC) sử dụng Phương pháp dùng để đánh giá độ mạnh tương tác H2 MIL-88s qua nhiệt hấp phụ Qst Đánh giá khả lưu trữ hydro chuỗi MIL-88s (với thành phần kim loại Fe), kết MIL-88D có tiềm cho khả lưu trữ hydro tính theo phần trăm trọng lượng (dung khối) với dung lượng hấp phụ toàn phần/bề mặt tương ứng 5,15/4,03 wt% 77 K 0,69/0,23 wt% 298 K, đánh giá theo dung tích MIL-88A lại tốt cho lưu trữ hydro (dung tích tồn phần/bề mặt tương ứng 50,69/44,32 g/L 77 K, 6,97/2,49 g/L 298 K) Kết luận án với việc thay Fe MIL-88A số kim loại chuyển tiếp nâng cao khả lưu trữ H2 kim loại tốt chuỗi kim loại khảo sát scandium (Sc) Cụ thể, kết lưu trữ toàn phần/bề mặt đạt 5,30/4,63 wt% 77 K 0,72/0,29 wt% 298 K tính theo dung khối; 51,99/45,51 g/L 77 K 7,08/2,83 g/L 298 K tính theo dung tích Khả lưu trữ hydro M-MIL-88A theo thứ tự giảm dần Sc-, Ti-, V-, Cr-, Mn-, Fe- Co-MIL-88A Kết nghiên cứu bước đầu cho thấy tiềm chuỗi MIL-88s cho lưu trữ hydro kết so sánh với nhóm vật liệu MOF đánh giá cao cho lưu trữ H2 đến Các kết giải thích khả hấp phụ hydro phụ thuộc mạnh vào đặc tính cấu trúc diện tích bề mặt riêng, thể tích lỗ rỗng MIL-88s Những đặc tính quan trọng cải thiện phù hợp tăng khả hấp phụ hydro MIL-88s v ACKNOWLEDGEMENTS This work couldn’t be completed without the help and support of many people to whom I would like to express my gratitude First of all, I would like to thank my supervisors, Dr Do Ngoc Son and Dr Pham Ho My Phuong at Ho Chi Minh City University of Technology in VNU-HCM (HCMUT), for their guidance and helpful comments throughout my doctorate course I am grateful to express my deepest appreciation to Dr Do Ngoc Son when I perform my research at HCMUT His enthusiasm, valuable suggestions and comments were very helpful during this research I would like to thank Prof Viorel Chihaia (Institute of Physical Chemistry “Ilie Murgulescu” of the Romanian Academy, Splaiul Independentei 202, Sector 6, 060021 Bucharest, Romania) for helpful comments to my research papers I acknowledge the usage of the computer time and software granted by the Institute of Physical Chemistry of Romanian Academy, Bucharest (HPC infrastructure developed under the projects Capacities 84 Cp/I of 15.09.2007 and INFRANANOCHEM 19/01.03.2009) I am very thankful to Prof Vo Van Hoang for helping me more advantageous in this work at the Computational Physics Laboratory I will also remember nice and fruitful conversations with other members of this Lab Additionally, I also would like to thank all lecturers and secretaries of Faculty of Applied Science, HCMUT giving me useful knowledge and helping during my research herein I am very thankful to the lecturers and co-workers at Department of Physics, Quy Nhon University (QNU) who helped me to have a chance to participate in PhD project at HCMUT and well my work at QNU I would like to acknowledge the financial support from Quy Nhon University and the Vallet scholarship foundation Last but not least, I would like to thank my beloved husband for taking care, understanding and sympathy He is the one who strongly believed in me, encouraged me to start the PhD project and was always with me in good and bad times I had during that four years I am grateful to my sons for understanding, sympathy and they are always lovely babies giving me a great motivation to complete this study I am also vi big thanks to other members in my family for understanding and helping me during the time for my PhD course This research was funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.01-2017.04; the research project T2015.460.05 of Quy Nhon University; and the research project TNCS-2015-KHUD-33 of Ho Chi Minh City University of Technology vii TABLE OF CONTENTS DECLARATION i ABSTRACT ii TÓM TẮT LUẬN ÁN iv ACKNOWLEDGEMENTS vi TABLE OF CONTENTS viii LIST OF FIGURES xi LIST OF TABLES xvii LIST OF ABBREVIATIONS xix INTRODUCTION 1 Motivation for study Structure of PhD dissertation CHAPTER 1: LITERATURE REVIEW OF METAL-ORGANIC FRAMEWORKS 1.1 General overview of metal-organic frameworks 1.1.1 Definition of metal-organic frameworks 1.1.2 Structural aspects of MOFs 1.1.3 History of MOFs 1.1.4 Nomenclature of MOFs 11 1.1.5 Current research of MOFs in Vietnam 12 1.2 Major applications of MOFs 13 1.2.1 Gas storage, capture, and separation 13 1.2.2 Biomedical applications 20 1.3 Overview of synthesis and research methods for MOFs 21 1.3.1 Synthesis methods for MOFs 21 1.3.2 Theoretical studies 23 1.4 MIL-88s for hydrogen storage 24 CHAPTER 2: COMPUTATIONAL METHODS 26 2.1 Density functional theory calculations 26 viii APPENDIX Table A1 The organic ligand/linker of MOFs Notation Formula/Explain ADS ADTP 2,6-anthracenedisulfonic acid 1,3,5,7-tetrakis(4-phosphonophenyl) adamantine BBC 4,4′,44″-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate BDC 1,4-benzenedicarboxylate 4,4’-bipy 4,4’-bipyridine BPCN 4,4' – bBiphenyldicarbonitrile BPDC 4,4’-biphenyl-dicarboxylate BPDS 4,4’-biphenyldisulfonic acid BPY 4,4’-dipyridyl BTB 1,3,5-benzenetribenzoate BTC 1,3,5-benzenetricarboxylate BTE 4,4′,4″-[benzene-1,3,5-triyl-tris (ethyne-2,1-diyl)] tribenzoat BTT 1,3,5-enzenetristetrazolate dabco 1,4-diazabicyclo[2.2.2]octane dcdBn 6,6'-dichloro-2,2'-dibenzyloxy-1,1'-binaphthyl-4,4'-dibenzoate dcdEt 6,6'-dichloro-2,2'-diethoxy-1,1'-binaphthyl-4,4'-dibenzoate DMF N,N'-dimethylformamide dobdc 2,5-dioxido-1,4-benzenedicarboxylate EDP 1,2-Ethylenediphosphonic acid FMA fumarate H4dhtp 2,5-dihydroxy-terephthalate H2hfipbb 4,4-(hexafluoroisopropylidene)-bis(benzoate) HMT hexamethylenetetramine NDC 2,6-naphthalenedicarboxylate oxdc oxydiacetate pda p-phenylenediacrylate Ted triethylenediamine 107 Table A2 Chemical formula of MOFs MOFs Formula/Explanation IRMOF-8 Zn4O(NDC)3 MOF-74 CPO-27 M2(dobdc) of M2(dhtp)) s = A, B, C or D M3O(L)3X; M is trivalent metal, X is halogen, L is the organic ligand MIL-88s such as: fumarate (FMA)/dicarbox (A), 1,4-benzene-dicarboxylate or BDC (B), 2,6-naphthalene-dicarboxylate or NDC (C), and 4,4’biphenyl-dicarboxylate or BPDC (D) MIL-100 Fe3O(BTC)2X, X = Cl, OH MIL-101 M3O(H2O)2(X)(BDC)3, với X = F, OH and M is the metal (Cr) Mn-BTT Mn3[(Mn4Cl)3(BTT)8MeOH]2 MOF-177 Zn4O(BTB)2 MOF-5 IRMOF-1 MOF4(Mg) Zn4O(BDC)3 Mg2(dobdc) MOF-200 Zn4O(BBC)2(H2O)3·H2O MOF-210 Zn4O(BTE)4/3(BPDC) NU-100 PCN-610 Cu3(ttei) PCN-61 Cu3(ntei) PCN-66 Cu3(btei) PCN-68 NOTT-116 SNU-50’ Cu3(ptei) Cu2(bdcppi) 108 Table A3 The name of metal-organic frameworks Notation Formula/Explain HKUST Hong Kong University of Science and Technology IRMOF-n MIL MOF-n Isoreticular Metal-Organic Framework (herein, n an integer referring to a member of the series) Materials of Institut Lavoisier Metal-Organic Framework (n an integer assigned in roughly chronological order) NENU North East Normal University China NU Northwestern University VNU Vietnam National University 109 Table A4 The maximum absolute and excess gravimetric H2 uptakes in MIL-88s at 77 K and 298 K and the pressures below 100 bar, shown in many other units (mmol/g and cm3/g) Uptakes (cm3/g) Uptakes (mmol/g) MOF MIL88A MIL88B MIL88C MIL88D 77 K 298 K 77 K 298 K Absolute Excess Absolute Excess Absolute Excess Absolute Excess 23.30 20.30 3.20 1.15 518.13 451.42 71.16 25.57 20.60 17.80 2.90 1.15 458.09 395.83 64.49 25.57 9.35 8.60 1.55 0.80 207.92 191.24 34.47 17.79 25.75 20.15 3.45 1.15 572.61 448.08 76.72 25.57 Table A5 The maximum absolute and excess gravimetric H2 uptakes in M-MIL-88A at 77 K and 298 K and the pressures below 100 bar, shown in many other units (mmol/g and cm3/g) Uptakes (cm3/g) Uptakes (mmol/g) MOF ScMIL88A TiMIL88A VMIL88A CrMIL88A MnMIL88A FeMIL88A [168] CoMIL88A [18] 77 K 298 K 77 K 298 K Absolute Excess Absolute Excess Absolute Excess Absolute Excess 26.50 23.15 3.60 1.45 589.29 514.80 80.05 32.24 25.45 22.45 3.45 1.30 565.94 499.23 76.72 28.91 24.75 21.85 3.35 1.25 550.38 485.89 74.50 27.80 24.45 21.60 3.30 1.20 543.70 480.33 73.38 26.68 23.85 20.75 3.25 1.15 530.36 461.43 72.27 25.57 23.30 20.30 3.20 1.15 518.13 451.42 71.16 25.57 23.00 20.00 3.15 1.10 511.46 444.75 70.05 24.46 110 H 0.37 Å 0.37 Å H COM q = 0.47 e  = 2.958 Å /kB = 36.7 K q = 0.47 e q = -0.94 e Figure A1 Electrostatic charges and LJ parameters for the H2 molecule according to the TraPPE force field Hydrogen molecule is modeled as a three-site rigid model at the center of mass (dH-H = 0.74 Å) Figure A2 DOS of the isolated hydrogen molecule Fermi level is set to zero Figure A3 Volume optimization for Fe-MIL-88A structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum relative energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio 111 Figure A4 Volume optimization for MIL-88B structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum relative energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio Figure A5 Volume optimization for MIL-88C structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum relative energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio Figure A6 Volume optimization for MIL-88D structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum relative energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio 112 H2 2.59 Å H2 3.41 Å 2.59 Å a) Side-on (Fe) b) End-on (Fe) H2 H2 3.38 Å 2.63 Å c) Side-on (hollow) d) End-on (hollow) H2 H2 2.92 Å 3.39 Å C C C e) Side-on (ligand) f) End-on (ligand) Figure A7 Most favourable adsorption sites of the H2 molecule in Fe-MIL-88A 113 H2 2.35 Å H2 2.35 Å 3.38 Å a) Side-on (Fe) b) End-on (Fe) H2 H2 3.63 Å 3.80 Å c) Side-on (hollow) d) End-on (hollow) H2 H2 H2 3.21 3.15 Å 3.27 Å e) Side-on (ligand) f) End-on (ligand) Figure A8 Most favourable adsorption sites of the H2 molecule in MIL-88B 114 H2 H2 2.51 Å 2.51 Å 3.07 Å a) Side-on (Fe) b) End-on (Fe) H2 H2 3.43 Å 3.56 Å c) Side-on (hollow) d) End-on (hollow) H2 H2 3.19 Å 3.40 Å C4 e) Side-on (ligand) f) End-on (ligand) Figure A9 Most favourable adsorption sites of the H2 molecule in MIL-88C 115 H2 H2 3.64 Å 3.45 Å 3.44 Å a) Side-on (Fe) b) End-on (Fe) H2 H2 3.06 Å 3.25 Å c) Side-on (hollow) d) End-on (hollow) H2 H2 3.67 Å 3.46 Å e) Side-on (ligand) f) End-on (ligand) Figure A10 Most favourable adsorption sites of the H2 molecule in MIL-88D 116 Figure A11 Volume optimization for Sc-MIL-88A structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio Figure A12 Volume optimization for Ti-MIL-88A structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio Figure A13 Volume optimization for V-MIL-88A structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio 117 Figure A14 Volume optimization for Cr-MIL-88A structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio Figure A15 Volume optimization for Mn-MIL-88A structure by Murnaghan fitting method: (a) Relative energy as a function of the lattice constant a for each c/a ratio, where the solid lines are the fitting curves, while the points are the calculated values by vdW-DF; The minimum energy points (fitted from (a)) are plotted versus (b) the lattice constant a and (c) the c/a ratio (a) Side-on configuration (b) End-on configuration Figure A16 Adsorption configurations of the hydrogen molecule in the M-MIL-88A structure: (a) side-on configuration and (b) end-on configuration 118 PDOS (states per eV) E-EF (eV) Figure A17 PDOS of the adsorbed H2 and the orbitals of metals of M-MIL-88A configurations at side-on site: (a) Sc, (b) Ti, (c) V, (d) Cr, (e) Mn, and (f) Fe 119 PDOS (states per eV) E-EF (eV) Figure A18 PDOS of the adsorbed H2 and the orbitals of carbon atoms of M-MIL-88A configuration at side-on site with the M is: (a) Sc, (b) Ti, (c) V, (d) Cr, (e) Mn, and (f) Fe 120 PDOS (states per eV) E-EF (eV) Figure A19 PDOS of the adsorbed H2 and the orbitals of oxygen atoms of M-MIL-88A configuration at side-on site with the M is: (a) Sc, (b) Ti, (c) V, (d) Cr, (e) Mn, and (f) Fe 121 ... significantly at ambient temperatures and low pressures These materials have been investigated and highly evaluated for various applications such as gas storage/ capture and separation of binary gas... such as alkali metal ions (Mg2+), alkaline-earth metal ions (Al3+) and rear-earth metal ions (In3 +, Ga3+) The important features of metal connectors are coordination numbers and coordination... areas, large pore volumes with the advantages of physisorptionbased materials are of particular interest for gas storage, especially in hydrogen storage So far, various MOF materials have proved