SỞ KHOA HỌC VÀ CƠNG NGHỆ TP HỒ CHÍ MINH VIỆN KHOA HỌC VÀ CƠNG NGHỆ TÍNH TỐN BÁO CÁO TỔNG KẾT NGHIÊN CỨU PHÁT TRIỂN VẬT LIỆU ZEOLITE KHUNG HỮU CƠ CỘNG HĨA TRỊ MỚI (Z-COFs) BẰNG TÍNH TỐN DFT TUẦN HỒN VÀ MƠ PHỎNG MONTE CARLO Đơn vị thực hiện: PTN Vật liệu Nano Khoa học Phân tử Chủ nhiệm đề tài: Phạm Trần Nguyên Nguyên TP HỒ CHÍ MINH, THÁNG 4/2020 SỞ KHOA HỌC VÀ CƠNG NGHỆ TP HỒ CHÍ MINH VIỆN KHOA HỌC VÀ CƠNG NGHỆ TÍNH TỐN BÁO CÁO TỔNG KẾT NGHIÊN CỨU PHÁT TRIỂN VẬT LIỆU ZEOLITE KHUNG HỮU CƠ CỘNG HÓA TRỊ MỚI (Z-COFs) BẰNG TÍNH TỐN DFT TUẦN HỒN VÀ MƠ PHỎNG MONTE CARLO Viện trưởng: Đơn vị thực hiện: PTN Vật liệu Nano Khoa học Phân tử Chủ nhiệm nhiệm vụ: Nguyễn Kỳ Phùng Phạm Trần Nguyên Nguyên TP HỒ CHÍ MINH, THÁNG 04/2020 MỤC LỤC Trang MỞ ĐẦU 03 ĐƠN VỊ THỰC HIỆN 04 KẾT QUẢ NGHIÊN CỨU I Báo cáo khoa học 06 II Tài liệu khoa học xuất 48 III Chương trình giáo dục đào tạo 49 IV Hội nghị, hội thảo 50 V File liệu 51 CÁC PHỤ LỤC 80 PHỤ LỤC 1: Bài báo 1: “Electron Delocalization in Single-Layer Phthalocyanine-Based Covalent Organic Frameworks: A First Principle Study”, RSC Advances, 2019, 9, 29440 PHỤ LỤC 2: Bài báo 2:” Design of Zeolite-Covalent Organic Frameworks for Methane Storage” Materials 2020, 13, 3322 Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page MỞ ĐẦU Xuất phát từ tính chất đa dạng cấu trúc thành phần hóa học vật liệu xốp-khung hữu cộng hóa trị (COF), COF hứa hẹn tạo vô số vật liệu khơng có khả làm vật liệu bán dẫn, chất xúc tác mà cịn có khả hấp phụ khí tốt có diện tích bề mặt riêng lớn Tuy nhiên thực tế, việc tổng hợp vật liệu COFs theo tính ứng dụng mong muốn cịn gặp nhiều khó khăn, việc khảo sát thực nghiệm đầy đủ tính chất chúng điều khơng dễ dàng tốn kém.Vì cần có đồng hành, hỗ trợ thông tin cấu trúc dự đốn trước tính chất vật liệu từ nghiên cứu lý thuyết Đó mạnh phương pháp nghiên cứu vật liệu khoa học tính tốn nói chung, hóa học tính tốn nói riêng Trong đề án này, kỹ thuật mơ tính tốn hóa học đại, kết hợp phương pháp động học phân tử, mô Monte Carlo Lý thuyết phiếm hàm mật nghiên cứu phát triển cấu trúc vật liệu COF-2D đơn lớp (Ni–phthalocyanine, NiPc) COF-3D cấu trúc Zeolite, tạm gọi vật liệu zeolite-COFs (Z-COFs) Các vật liệu nghiên cứu định hướng cho hai ứng dụng chính: vật liệu bán dẫn lưu trữ khí metan Các cấu trúc Z-COFs đề xuất đề án, thời điểm theo tìm hiểu chúng tơi hồn tồn chưa nghiên cứu kể thực nghiệm lý thuyết, hội phát triển vật liệu COF tiềm cho định hướng ứng dụng quan tâm Hơn thế, cấu trúc tiềm thiết kế sau sàng lọc tính tốn thơng số liên quan đến độ bền nhiệt động vật liệu phương pháp DFT tuần hồn hệ thống siêu máy tính Nhật, làm sở đánh giá khả tồn vật liệu Đây thông tin cần thiết cho thực nghiệm việc nghiên cứu tổng hợp loại vật liệu lại đề cập đến cơng trình cơng bố, điểm mạnh đóng góp dự án mặt khoa học Chiến lược thiết kế vật liệu Z-COF Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page Lời cảm ơn đến ICST Chúng xin gửi lời cám ơn chân thành sâu sắc đến Viện Khoa học Cơng nghệ Tính tốn (ICST), Sở Khoa học Cơng nghệ TpHCM cung cấp kinh phí tạo điều kiện thuận lợi cho thực tốt nhiệm vụ đề tài Trân trọng cám ơn Thay mặt nhóm nghiên cứu Chủ nhiệm NV: Phạm Trần Nguyên Nguyên Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page ĐƠN VỊ THỰC HIỆN Phịng thí nghiệm: Vật liệu Nano Khoa học Phân tử (Open Lab) Chủ nhiệm đề tài: Phạm Trần Nguyên Nguyên Thành viên đề tài: Phạm Quang Hưng Nguyễn Thị Minh Thi Đỗ Hữu Hà Lê Quang Đông Nguyễn Thị Thanh Loan Cơ quan phối hợp: ĐH Khoa học Tự Nhiên Tp Hồ Chí Minh Viện nghiên cứu vật liệu Tohoku, Nhật Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page KẾT QUẢ NGHIÊN CỨU I BÁO CÁO KHOA HỌC Trong nhiệm vụ thực hai chủ đề i) Phát triển vật liệu COF-2D cho định hướng vật liệu dẫn, ii) Phát triển vật liệu COF-3D cho định hướng hấp phụ khí metan Sau báo cáo chi tiết số kết đạt được: I.1 Phát triển cấu trúc vật liệu COF-2D đơn lớp (Ni–phthalocyanine, NiPc) cho hướng vật liệu dẫn Kết nghiên cứu công bố báo (Đính kèm Phụ lục 2) 1.1 Giới thiệu Sự thành công Graphene mở lối cho vật liệu 2D Tuy vậy, việc không tồn vùng cấm vùng dẫn vùng hóa trị lại khiến cho Graphene cản trở khả ứng dụng khả dẫn cao tính chất học tốt Điều dẫn đến hai chiến lược chính: (1) tinh chỉnh cấu trúc Graphene để độ rộng vùng cấm khác khơng (2) tìm kiếm vật liệu thay thỏa mãn yêu cầu đề Vật liệu khung hữu ứng cử viên tốt cho việc tìm kiếm cấu trúc tiềm lẽ tính đa dạng hóa học Tuy vậy, tính đến thời điểm với hiểu biết chúng tơi chưa vật liệu khung hữu công bố có linh độ vượt mức 10 cm2/(V.s) Bằng cách xây dựng cấu trúc dựa đơn vị cộng hưởng phthalocyanine, cấu trúc NiPc–P, NiPc–2P, NiPc–3P tối ưu hóa cấu trúc hình học xem xét khả tổng hợp dựa tính tốn lượng tử Hình 1: (a) Cấu trúc tinh thể ô mạng 2x2 NiPc-1P (b) vùng Brillouin thứ vật liệu (c) ô mạng vật liệu NiPc-2P (d) NiPc-3P (nguyên tử Ni màu đỏ sậm, N màu xanh dương,C màu xám nguyên tử H loại bỏ để hình ảnh rõ ràng) Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page 1.2 Phương pháp nghiên cứu Tính tốn tối ưu hóa thực khuôn khổ lý thuyết phiếm hàm mật độ DFT phần mềm CRYSTAL09 Phiếm hàm B3LYP chọn với tập sở pob-TVZP dành cho nguyên tố Ni, S, O, N, C H Riêng tập sở dành cho nguyên tố Mo sử dụng từ nghiên cứu cúa nhóm Towler phát triển trước Do cấu trúc tinh thể liên xếp chặt phân tử tập sở dành cho Mo bị loại trừ hàm sp phân tán (mũ số nhỏ 0.1), sau tách thành hai hàm s p tối ưu với đoạn mã nhóm Billy Mạng đảo tính tốn với lưới Monkhorst mật độ 2π × 0.02 Å-1 Về trình tự hợp, mức hội tụ 10-10 a.u chọn cho tiêu chí lượng Ngưỡng tính tốn xác định tích phân Coulomb trao đổi 10-7, 10-7, 10-7, 10-7, 10-16 a.u tương ứng với từ khóa TOLONTEG 7 7 16 Để xác định tính bền cấu trúc cấu trúc tối ưu hóa có phải điểm dừng bề mặt hay khơng, tính tốn phonon thực với ô mạng lớn 3x3 tần số dao động Γ @ Tính tốn biến dạng Trong tính tốn này, thời gian τ giả định phonon nhánh âm Độ cứng mặt tính tốn cách hồi quy lượng từ ô mạng hàm bậc theo sức căng: dành cho hệ vật liệu 2D dánh cho hệ vật liệu 1D Với So lo diện tích độ dài cấu trúc 2D and 1D tối ưu hóa Độ cứng vật liệu 2D 1D tính tốn từ hệ số phương trình hồi quy: dành cho hệ vật liệu 2D dánh cho hệ vật liệu 1D C2D C1D có đơn vị J/m2 J/m Hằng số biến dạng E1 tính tốn theo phương pháp tương tự Vùng hóa trị ứng với lượng cao vùng dẫn ứng với lượng thấp hàm số theo sức căng: cho vận tải lỗ trống Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page cho vận tải electron Khối lượng hiệu dụng dành cho lỗ trống (hoặc electron) tính cách hồi quy lượng vùng hóa trị (hoặc vùng dẫn) vào hàm parabol: Nên lưu ý khối lượng hiệu dụng ten-xơ giá trị bị phụ thuộc vào chiều mà ta chọn hồi quy Để tính linh độ riêng chất mang theo lý thuyết biến dạng, việc hồi quy vùng lượng phải chiều với sức căng Trong tính tốn này, giới hạn sức căng Δl/lo khoảng 5% cho độ cứng 1% cho tính tốn biến dạng Với tính tốn khối lượng hiệu dụng, vectơ sóng k bị giới hạn khoảng 0.05 Bohr-1 gần cực trị vùng lượng Sỡ dĩ ngưỡng tính tốn hồi quy đặt nhầm mục đích tránh sai lệch lý thuyết biến dạng Những chi tiết dự đoán linh độ chất mang theo lý thuyết vật liệu hữu nano tìm thấy nhiều tài liệu nghiên cứu trước @ Tính linh độ chất mang: Phương trình vận chuyển Boltzmann lý thuyết biến dạng ứng dụng để tính linh độ chất mang nồng độ thấp Với vật liệu chiều, linh độ chất mang theo phương với sức căng tính cơng thức: Trong đó, , , độ cứng mặt, khối lượng hiệu dụng, số lý thuyết biến dạng , , , số điện tích, số Plank, số Boltzmann nhiệt độ tuyệt đối Viện Khoa học Cơng nghệ Tính tốn TP Hồ Chí Minh Page 1.3 Nội dung nghiên cứu & kết đạt 1.3.1 Xây dựng tối ưu hóa cấu trúc COF-2D Hình trình bày phàn ứng tổng hợp đồng bay vật liệu COF-2D đơn lớp NiPc-P, NiPc-2P, NiPc-3P Hình 2: Phản ứng đồng bay tổng hợp vật liệu NiPc-P, NiPc-2P, NiPc-3P Các thơng số cấu trúc tối ưu hóa cho vật liệu đơn lớp trình bày Bảng Bảng Bảng Hằng số mạng vị trí ngun tử mạng (nhóm khơng gian P4/mmm) dành cho vật liệu đơn lớp NiPc-P, NiPc-2P, and NiPc-3P C C C H N N Ni NiPc-P a = 10.591 Å x y 0.60480 0.75876 0.88972 0.56637 0.00000 0.63627 0.00000 0.73838 0.72431 0.72431 0.50000 0.68157 0.50000 0.50000 C C C C H N N Ni NiPc-2P a = 13.040 Å x y 0.09401 0.60891 0.58534 0.71041 0.81685 0.55412 0.00000 0.55549 0.09472 0.69197 0.68231 0.68231 0.50000 0.64791 0.50000 0.50000 Viện Khoa học Công nghệ Tính tốn TP Hồ Chí Minh H H C C C C C N N Ni NiPc-3P a = 15.482 Å x y 0.00000 0.66015 0.15892 0.66196 0.00000 0.59004 0.07867 0.54674 0.15830 0.59198 0.57196 0.67733 0.76704 0.54582 0.65362 0.65362 0.50000 0.62476 0.50000 0.00000 Page View Article Online Open Access Article Published on 18 September 2019 Downloaded on 11/12/2019 2:00:11 PM This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence RSC Advances ˚ for NiPc-P is in excellent calculated Ni–N bond length of 1.923 A ˚ from the agreement with the PBE+U bond length of 1.922 A 29 previous calculation Our calculated band gap at B3LYP level for NiPc-P is 0.55 eV which is slightly higher than the PBE+U band gap of 0.34 eV by Zhou and Sun.29 However, it has been shown that for the extended organic frameworks B3LYP gives a more consistent result in comparison with the experiment.59,60 The band gap for NiPc-2P and NiPc-3P are 0.73 and 0.82 eV, respectively (Fig 5) Hence, expanding the link, i.e., increasing the number of the benzene units, gradually widens the gap between the band edges Interestingly, the trend in single-layer NiPc is opposite to what have previously observed in the boroxine-based COFs in which increasing the number of benzene ring reduces the band gap Moreover, the band edges of NiPc-2P are at G instead of M as those of NiPc-P and NiPc-3P even though they share the same space group symmetry Three NiPc structures exhibit highly dispersive VBM and CBM with a width of 0.94–1.77 eV and 0.62–1.3 eV, respectively Not surprisingly, the bands are less dispersive as the unit cell becomes larger by expanding the linkers This implies the highly electron delocalized states, thereby favoring a band-like transport mechanism of charge carrier From the density of states plot (Fig 5), we can see that both C and N contribute to the CBM, whereas VBM is dominated by the C atoms Loosely speaking, this suggests that the phthalocyanine mainly contribute to the conduction band, in contrast, the benzene units are dominant in the valence band Furthermore, Ni plays a negligible role in the band edges, suggesting that electron and hole primarily transport along the organic backbone Since the band-like transport is most likely the primary mechanism, we further compute the charge carrier mobility along the organic backbone to quantify the transport property of NiPc in the next section 3.3 Intrinsic charge carrier mobility We compute the intrinsic electron and hole mobility NiPc along the organic backbone The effective masses are obtained by tting the band edges along the appropriate k-point path, i.e., G–X for NiPc-2P, X–M for NiPc-P and NiPc-3P The deformation potential (DP) constant E1 and the in-plane stiffness C2D are calculated by Paper means of the constant strain rate approach Owing to the uncertainty of the method as well as the lack of the experimental value, we also perform the calculation on the trigonal prismatic molybdenum disulphide (1H MoS2) sheet sing the same procedure for the sake of comparison (Table 2) The calculated mobility for MoS2 are 117 and 422 cm2 V1 s1 for electron and hole, respectively, which are in excellent agreement with the previous work.5,38,61 The charge mobility calculation for MoS2 can be found in section S6 of the ESI.† For NiPc-P, the hole mobility of 61.7 103 cm2 V1 s1 is two order of magnitude larger than that of electron, i.e., 252 cm2 V1 s1 A similar trend is observed for NiPc-2P or NiPc-3P, suggesting that the NiPc structures are hole conducting materials with exceptionally high mobility NiPc's electron and hole mobility are in the same order of magnitude with the theoretical mobility of phosphorene9 and that of graphdiyne ribbons.62 As more benzene are added between the phthalocyanine units, the electron-acoustic phonon scattering becomes stronger as indicated by the smaller in-plane stiffness (Table 2) As a result, it is expected that the electron and hole mobility should become smaller Surprisingly, the electron mobility is increasing, whereas an opposite trend is observed for the hole mobility This can be explained by the substantial reduction in the electron mass as the conjugated bridge is extended On the contrary, the hole mass is slightly increasing This large change in the electron mass is in line with Table DP constant E1, in-plane stiffness C2D, effective mass, and intrinsic charge carrier mobility for the single-layer NiPc and MoS2 E1 (eV) C2D (J m2) m* (me) 1 1 m2D s ) b (cm V Electron NiPc-P NiPc-2P NiPc-3P MoS2 3.39 3.25 3.29 9.21 237 206 179 160 1.08 0.82 0.60 0.48 252 409 657 117 Hole NiPc-P NiPc-2P NiPc-3P MoS2 2.36 2.62 2.15 3.85 237 206 179 160 0.10 0.13 0.16 0.60 61 700 25 000 21 700 422 Electronic band structure and density of states (DOS) for NiPc-P, NiPc-2P, and NiPc-3P The work functions (F) are also presented The VBM and CBM are highlighted in red Fig 29444 | RSC Adv., 2019, 9, 29440–29447 This journal is © The Royal Society of Chemistry 2019 View Article Online Open Access Article Published on 18 September 2019 Downloaded on 11/12/2019 2:00:11 PM This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence Paper the fact that the linker expansion separates the phthalocyanine units which is the main constituent of the conduction band as shown in the DOS Therefore, the hole mobility is determined by the scattering process with phonon, meanwhile the electronic velocity (hħk/m*) controls the electron mobility of the NiPc compounds To further conrm the band-like charge transport along the organic backbone, we also compute the charge mobility for the one-dimensional forms of NiPc, namely 1D-NiPc (Fig 6) Unlike their two-dimensional counterparts, the band gaps are decreasing as the link is expanded However, the same argument can be applied, specically the electron mobility is determined by the electronic velocity The band edges of 1DNiPc-2P are at G instead of X as for 1D-NiPc-P and 1D-NiPc-3P; this swapping of band edge positions is in line with the similar observation for the single-layer NiPc discussed above In comparison with the single-layer NiPc, the one-dimensional forms show much lower charge carrier mobilities (Table 3) However, they are also hole conducting materials due to large hole mobility compared to that of electron Both single-layer and one-dimensional NiPc structures possess high charge carrier mobilities, conrming the band-link transport mechanism of charge carriers along the organic frameworks 3.4 Mechanical and thermodynamical stability In addition to the intriguing electronic and electric properties, NiPc are mechanically stable Indeed, the computed in-plane stiffness (C2D) implies that the NiPc-3P is as stiff as MoS2 Remarkably, the in-plane stiffness for NiPc-P and NiPc-2P is Fig One dimensional structure (ribbon) of NiPc (a) and their electronic band structures (b) The Fermi level is set to zero The VBM and CBM are highlighted in red This journal is © The Royal Society of Chemistry 2019 RSC Advances Table DP constant E1, stretching modulus C1D, effective mass, and intrinsic charge carrier mobility for 1D-NiPc E1 (eV) C1D (107 J m1) m* (me) 1 1 m1D s ) b (cm V Electron NiPc-P NiPc-2P NiPc-3P 6.70 10.32 10.17 2.40 2.30 2.22 0.28 0.85 0.73 181 14 17 Hole NiPc-P NiPc-2P NiPc-3P 5.82 6.58 5.43 2.40 2.30 2.22 0.15 0.15 0.14 619 465 684 1.50 and 1.29 times higher than that of MoS2, respectively Expanding the link induces a reduction in the NiPc's stiffness Our calculated in-plane stiffness for NiPc-P is about three times higher than the previous prediction on Pc-P.58 To explain this discrepancy, we compute the stiffness for Pc-P and compare it to that of NiPc-P using the same approach Our result shows that our calculated C2D for Pc-P and NiPc-P are very similar (see section S9 of the ESI†) Hence, Ni plays a minor role in the mechanical property of single-layer NiPc-P and the disparity with previous work is because of the difference in the level of theory employed In order to validate the accuracy of the current approach, we compute mechanical properties for single-layer MoS2 and graphene whose experimental values are accessible In fact, our estimated Young's modulus for MoS2 using a thickness of 0.65 nm, however, is 246 GPa, which is very consistent with the experimental value of 270 100 GPa.63 For graphene (see section S9 of the ESI†), its calculated stiffness of 390 J m2 agrees very well with the reported values of ca 350– 370 J m2 from the literatures.64–66 The agreement with the experimental measurements conrms the accuracy of our calculations and the predicted mechanical properties for NiPc COFs are reliable Last but not least, NiPc are thermodynamically stable and can be formed via co-evaporation between Ni and tetracyano linkers (Scheme 1) In fact, our proposed reaction is inspired by a similar approach used to synthesize Fe-phthalocyanine structure by Abel and co-worker.27 The Gibbs free energy at 400 K and atm are signicantly negative, suggesting that the Co-evaporation of Ni and the corresponding tetracyano linkers resulting in single-layer NiPc-P, NiPc-2P, and NiPc-3P Scheme RSC Adv., 2019, 9, 29440–29447 | 29445 View Article Online RSC Advances Paper Open Access Article Published on 18 September 2019 Downloaded on 11/12/2019 2:00:11 PM This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence Table Thermodynamic quantities at 400 K and atm for the formation reactions in Scheme NiPc-P NiPc-2P NiPc-3P DS (cal mol1 K1) DH (kcal mol1) DG (kcal mol1) 182 188 195 304 289 281 231 213 203 formation reactions are thermodynamically favored (Table 4) Furthermore, the same observation is preserved at higher temperatures as show in the section S4 of the ESI.† Hence, our result demonstrates a possible way to realize these fascinating materials in the laboratory Conclusions In summary, we have studied the electronically localized character of some typical building units in COFs chemistry Next, we have investigated the electronic structure and charge transporting property for three single-layer phthalocyanine-based COFs in which the electrons are fully delocalized over the entire material We have shown that these organic structures are promising two-dimensional materials with exceptional high carrier mobility and good mechanical stability in comparison with the renowned inorganic atom-thick materials such as MoS2 and phosphorene Most importantly, their properties can be tuned by systematically expanding the building unit via adding benzene to the organic linker Our delocalization argument highlights the importance of a good understanding of the electronic structure of the building linkages in designing new conducting COFs One can straightforwardly inspect the electronic delocalization of the potential linker, for example, using a KS-DFT calculation or a conjugation argument on the chemical structure Also, a systematic screening on a large set of organic linkages from the computational perspectives can offer outstanding candidates to construct new frameworks with desired properties, and this is under investigation Another interesting direction would be modifying the organic backbones with different functional groups to tune the electronic structure as well as the transporting properties of this class of materials We believe that our work has provided a theoretical insight into the design principle of conducing single-layer COFs for optoelectronic applications Conflicts of interest The authors declare no competing nancial interests Acknowledgements The authors are grateful for the supercomputing support from the Institute for Material 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02841, Korea Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam Faculty of Chemistry, University of Science, VNU-HCM, Ho Chi Minh City 700000, Vietnam Correspondence: sooyoungkim@korea.ac.kr (S.Y.K.); levanquyet@dtu.edu.vn (Q.V.L.); ptnnguyen@hcmus.edu.vn (N.-N.P.-T.) Received: 26 June 2020; Accepted: 24 July 2020; Published: 26 July 2020 Abstract: A new type of zeolite-based covalent organic frameworks (ZCOFs) was designed under different topologies and linkers In this study, the silicon atoms in zeolite structures were replaced by carbon atoms in thiophene, furan, and pyrrole linkers Through the adoption of this strategy, 300 ZCOFs structures were constructed and simulated Overall, the specific surface area of ZCOFs is in the range of 300–3500 m2 /g, whereas the pore size is distributed from to 27 Å Furthermore, the pore volume exhibits a wide range between 0.01 and 1.5 cm3 /g Screening 300 ZCOFs with the criteria towards methane storage, 11 preliminary structures were selected In addition, the Grand Canonical Monte Carlo technique was utilized to evaluate the CH4 adsorption ability of ZCOFs in a pressure ranging from to 85 bar at a temperature of 298 K The result reveals that two ZCOF structures: JST-S 183 v/v (65–5.8 bar) and NPT-S 177 v/v (35–1 bar) are considered as potential adsorbents for methane storage Furthermore, the thermodynamic stability of representative structures is also checked base on quantum mechanical calculations Keywords: ZCOFs; methane storage; porous materials; simulation; design Introduction Methane is known as the fundamental ingredient of natural gas which is found with oil fields in Earth’s crust Currently, methane is also exploited from methane hydrate, recognized as a promising resource to provide energy in the future However, efficiency and safety are two critical criteria for methane storage that need to be addressed in practical applications Therefore, a large number of studies have focused on methane storage with porous materials such as covalent organic frameworks (COFs), zeolitic imidazole frameworks, hydrogen-bonded organic frameworks, and metal-organic frameworks (MOFs) [1–6] In 2006, ZIFs were firstly reported with various topologies such as sod, rho, and mer [7] This study opened a new window for the synthesis of porous material as well as their applications In addition, zeolite-like MOFs (ZMOFs) were also simulated and prepared with different zeolite frameworks [8,9] For example, two anionic ZMOFs, including rho-ZMOF and sod-ZMOF were fabricated successfully by Liu et al [8] These materials have a high surface area which can provide exceptional gas adsorption such as H2 , CH4 , and CO2 Therefore, ZCOFs are evaluated as potential porous materials for gas storage Materials 2020, 13, 3322; doi:10.3390/ma13153322 www.mdpi.com/journal/materials Materials 2020, 13, 3322 of 11 Over the past decade, COFs have become interesting materials in the porous material group due to their outstanding specific surface area Similar to MOF, COFs have crystal structures with controllable pore sizes [10] However, COFs have a definite advantage that they only contain non-metal elements such as C, Si, B, O, and H These elements were linked together by a vast number of covalent bonds to form COFs structures In 2005, the first COF materials were synthesized by Yaghi et al., using the solvothermal method [10] Later, many researchers tried to expand the ability to synthesize COFs in different ways [11] Similar to MOFs, COFs have been scrutinized in a wide range of utilizations such as gas storage [12–16], catalysis [17,18], and sensors [19,20] due to their feature properties such as high thermal durability, large surface area, and low density [15] For example, COF-108 displayed a very low density of 0.17 g·cm−3 which is lower than any reported materials [21–23] COF-105 gave a high surface area of over 6000 m2 ·g−1 [21] The US Department of Energy (DOE) proposed a standard of the CH4 adsorption ability for porous materials to be 180 V(STP)/V, (where STP is the standard temperature and pressure) [24] On the theoretical study side, Goddard et al successfully designed two materials with appropriate functional groups to enhance the methane storage properties of some COF materials [25] That was, COF-103-Eth-trans and COF-102-Ant with methane adsorption capacity exceeding the target set by the DOE (Figure S1) Another group, Jing Hao Hu et al., modified COF-102 with a double halogen substitution [26] Their simulation result shows that the methane adsorption capacity of COF-102-1,4-2I is 181 V (STP)/V In addition, a few porous materials have been fabricated experimentally which surpassed the DOE standard, such as Ni-MOF-74 [27] (190 v(STP)/v) and PCN-14 [28] (220 v(STP)/v) Recently, a new DOE target has been provided for methane storage to be 315 cm3 /cm3 (at (35–1 bar) or (65–5.8 bar)) for the single crystal material [29,30] To date, there was not any experimental COFs, which can overcome the DOE target Therefore, several efforts related to the porous materials were conducted to find outstanding candidates for methane storage For instance, Zhao et al used the various functional groups involving –CF3 , –CH3 , -CN, -OCH3 , -CN, -Cl, Br, I, and NH2 to improve the methane adsorption ability of three-dimensional COFs [31] The result indicated that COF-102-I exhibited the highest CH4 uptake among the modified materials Martin et al generated a large number of porous polymer networks (~18,000 structures) for CH4 adsorption However, only three structures achieved the CH4 adsorption of 180 cm3 /cm3 [32] This result implied that finding excellent materials for methane storage is a great challenge for scientists Herein, under the support of computer tools, we proposed a strategy design of COF materials with different zeolite frameworks to find potential COF materials that are capable of methane storage reaching the DOE target We also demonstrate the survival of selected COFs from rational design, which provides useful information for experimental studies Design Strategy and Methodologies Figure illustrates the designed strategy of the covalent organic framework from the zeolite frameworks Replacing the silicon atom in 100 selected zeolite framework types by carbon from thiophene (Figure S2), furan, and pyrrole linkers, 300 ZCOF structures were constructed Since the topology of ZCOFs is inherited by the zeolite framework types, we named the newly designed materials, such as YYY-S, YYY-O, and YYY-N Therein, YYY stands for the framework type code of the zeolite, -S, -O, -N stand for thiophene, furan, and pyrrole, respectively Figure illustrates the designed strategy of the covalent organic framework from the zeolite frameworks Replacing the silicon atom in 100 selected zeolite framework types by carbon from thi Materials 2020, 13, 3322 of 11 Figure Graphical illustration of the design strategy for zeolite-based covalent organic frameworks (ZCOFs) materials The spheres in black, pink, and yellow denote C, H, and S (or O, N-H) atoms, respectively The ZCOF structures are built and optimized through the universal force field via forcite tools [33] The pore diameter (Dpore), accessible surface area (Sacc), and pore volume (Vpore) are calculated by the ZeO++ code A spherical model with a radius of 1.8405 Å was used to simulate the N2 molecule [34,35] All grand canonical Monte Carlo (GCMC) computations were conducted by utilizing the MUSIC code [36] The potential energy between the COF-CH4 and CH4 -CH4 was obtained from van der Waals interactions since CH4 is the poor polar molecule The CH4 molecule is simulated as a sphere with a kinetic diameter of 3.8 Å [37] Lennard-Jones potential was used with the parameters acquired from the transferable force fields (TraPPE) [38] for CH4 and Universal Force field for the atoms in the ZCOFs [33] The distances are more considerable than 12.8 Å, not considered in this model The parameters for interactions between the atoms of ZCOFs and CH4 molecules were estimated through the Lorentz-Berthelot rule [39] In the simulation, a supercell × × of COF was kept rigid, CH4 was considered a ‘spherical molecule’ For each pressure point, 15 × 106 Monte Carlo trial moves were performed This technique has been successfully applied for adsorption studies, reported in the previous works [40] The variables of force field for ZCOFs and CH4 are provided in Table The detailed parameters and structures of ZCOF were shown in Table S1 in the supplementary information Table The parameters of force field for ZCOF and CH4 Molecule CH4 ZCOFs Atom ε/kb (K) σ (Å) ref C H S O N 148.0 52.8 22.1 137.9 30.2 34.7 3.73 3.43 2.57 3.59 3.12 3.26 [38] [33] - Implementing the density functional theory (DFT) for periodic systems in CRYSTAL17 was used for the study of the structural stability of new ZCOFs [41,42] Specifically, the calculations were executed with the exchange-correlation functional of Perdew-Burke-Ernzerhof (PBE), and a basic set of 6-31G functions for atoms in the ZCOF structures The values of 0.00030 and 0.00045 are indications of the convergence criteria of force for a root-mean-square and maximum component of the gradient, respectively, whereas, the condition was set to 10−7 Hatrees during the geometry optimization for self-consistent total energy calculations (NPT-S, JST-S code) Materials 2020, 13, 3322 of 11 Results and Discussion 3.1 Screening ZCOFs for Methane Storage Figure provides information about Dpore, Sacc, and Vpore of 300 ZCOF structures The pore sizes of these ZCOFs cover a range from to 27 Å, and most ZCOFs have a pore size of about 8–14 Å, whereas the distribution of the surface area revealed that most ZCOFs exhibited the high surface area between 1000 and 2000 m2 /g and extended to nearly 3500 m2 /g This is well because the Sacc of zeolite is often lower than 900 m2 /g Notably, RWY-N displayed the largest surface area of 3437 m2 /g among 300 ZCOF materials However, the pore volume of ZCOF is not much higher than that of zeolite and most are less cm3 /g Materials 2020, 13,than x of 11 Figure Statistical analysis of all 300 ZCOFs constructed: (a) Accessible surface area; (b) pore size; Figure Statistical analysis of all 300 ZCOFs constructed: (a) Accessible surface area; (b) pore size; (c) pore volume (c) pore volume Using the screening parameters for methane storage materials in the work of Martin et al [32], /g, a total the screening parameters storage materials in the work of Martin et al were [32], suchUsing as Dpore > 10 Å, Sacc > 2000 m2for /g, methane and Vpore > 0.4 cm of 11 ZCOF candidates such as Dpore > 10 Sacc > 2000 m /g,The andparameters Vpore > 0.4 /g, a total of 11 ZCOF candidates were2 selected through 300Å,designed ZCOFs of cm 11 ZCOF structures are provided in Table selected through 300 designed ZCOFs The parameters of 11 ZCOF structures are provided in Table Materials Materials 2020, 2020, 13, 13, x3322 55 of of 11 11 Table The porous properties, total methane uptake, and delivery capacity of the 11 selected ZCOF Table The porous properties, total methane uptake, and delivery capacity of the 11 selected structures ZCOF structures Total Uptake Delivery capacity Total Uptake Delivery Sacc Dpore Vpore Delivery Total Uptake Delivery Capacity Total Uptake ZCOFs At 35 bar 35–1 bar At 65 bar Capacity Sacc Dpore (cm3Vpore (Å) /g) 3at 35 3bar 3/cm3bar 3) Capacity 65 bar ZCOFs (m /g) ) ) (cm35–1 (cmat3/cm 65–5.8 bar (m2 /g) (Å) (cm3 /g) (cm /cm 65–5.8 bar (cm3 /cm3 ) (cm3 /cm3 ) (cm3 /cm3 ) BOZ-S 2579 16.1 0.516 191 174 227 152 BOZ-S 2579 16.1 0.516 227 152 JSR-N 2865 12.8 0.543 197191 174174 231 150 JSR-N 2865 12.8 0.543 197 174 231 150 JSR-O 2702 12.4 0.489 187 170 221 151 JSR-O 2702 12.4 0.489 187 170 221 151 JSR-S 2480 13.6 0.612 179 168 220 164 JSR-S 2480 13.6 0.612 179 168 220 164 JST-S 2615 10.7 0.433 179179 169169 230 183 JST-S 2615 10.7 0.433 230 183 NPT-S 2548 19.5 0.502 227 145 NPT-S 2548 19.5 0.502 194194 177177 227 145 OBW-N 2920 13.8 0.451 221 134 OBW-N 2920 13.8 0.451 191191 166166 221 134 OBW-S 2734 15.7 0.557 191 174 226 148 OBW-S 2734 15.7 0.557 191156 174147 226 148 RWY-N 3437 24.2 1.212 206 161 RWY-N 3437 24.2 1.212 156 147 206 161 RWY-O 3273 22.8 1.055 158 149 208 163 RWY-O 3273 22.8 1.055 158 149 208 163 RWY-S 3209 26.5 1.419 135 129 189 156 Bulk RWY-S 320926.51.419 135 34 12933 18966 156 61 CH44 34 33 66 61 Bulk CH 3.2 Adsorption Adsorption of of CH CH44 3.2 The CH CH44adsorption adsorptioncapacity capacityatat298 298 selected ZCOFs illustrated in Figure The KK forfor thethe 11 11 selected ZCOFs waswas illustrated in Figure We3 We realize adsorption isotherm theselected selectedZCOFs ZCOFsisis quite quite close close together Methane realize thatthat the the adsorption isotherm of of the together Methane adsorption of of most most of of the ZCOFs ZCOFs rapid growth in the range of 0–20 bar then then increases increases slowly slowly and and adsorption 0-20 bar reaches equilibrium equilibrium at at aa pressure pressure of of about about 60 60 bar bar However, However, three three ZCOF ZCOF crystal crystal structures: structures: RWY-O, RWY-O, reaches RWY-N, and RWY-S RWY-S with an increasing pore diameter (as shown in Figure 4, Figure S3), have shown shown RWY-N, lower methane uptake compared to the other ZCOFs This can be explained via their pore size, the lower methane uptake compared to the other ZCOFs This can be explained via their pore size, the ZCOF with with aa large large pore pore size increases increases the the distance distance of of methane methane and and active active sites, sites, leading leading to to the the weak weak ZCOF interactions Thus, Thus, the thetoo-large too-large pore pore diameter diameter was was not not favorable favorable in inthe themethane methanestorage storageapplication application interactions Figure 3 Isotherms Isotherms of of total total CH CH44adsorption adsorptionin inaapressure pressureranging ranging from from 11 to to 85 85 bar bar at at aa temperature temperature of of Figure 298 K of 11 ZCOFs (a) XXX-S; (b) XXX-O and XXX-N 298 K of 11 ZCOFs (a) XXX-S; (b) XXX-O and XXX-N Materials 2020, 13, 3322 Materials 2020, 13, x of 11 of 11 Figure ZCOF crystal structures of RWY-O, RWY-N, and RWY-S The spheres in black, pink, red, blue, Figure ZCOF crystal structures of RWY-O, RWY-N, and RWY-S The spheres in black, pink, red, and orange denote C, H, O, N, and S atoms, respectively The yellow balls represent the pore size blue, and orange denote C, H, O, N, and S atoms, respectively The yellow balls represent the pore size In 11 selected ZCOF structures, JSR-N has the highest adsorption capacity at 35 bar with 197 and 231 (v/v) at 65 bar and followed by BOZ-S, OBW-S, JSR-O, and OBW-N In addition, the bulk density of In 11was selected ZCOF structures, JSR-N hasline thefor highest adsorption capacity 35 bar with that 197 methane also illustrated by a black dotted comparison purposes It is at clearly shown and 231are (v/v) at 65 bar and followed by BOZ-S, OBW-S, JSR-O, and OBW-N In addition, the bulk ZCOFs effective adsorbents for methane storage applications density of methane was also illustrated by a black dotted line for comparison purposes It is clearly 3.3 Methane Delivery shown that ZCOFs areCapacity effective adsorbents for methane storage applications The methane delivery capacity of the ZCOF selected structures is calculated as follows [32]: 3.3 Methane Delivery Capacity DC delivery (35–1) = the CH4 adsorption atselected 35 bar −structures the CH4 adsorption at 1asbar The methane capacity of the ZCOF is calculated follows [32]: (1) (35–1)== the the CH CH4 adsorption at 35 bar − the CH4 adsorption at bar DCDC (65–5.8) adsorption at 65 bar − the CH4 adsorption at 5.8 bar (1) (2) DC (65–5.8) = the CH4 adsorption at 65 bar − the CH4 adsorption at 5.8 bar (2) Table presents the delivery capacity of 11 ZCOF structures, which exhibited excellent performances for methane storage In total, NPS-S and JST-S give the best methane uptake, as shown in Figure 5a In particular, Figure 5b indicated that NPT-S gave the largest DC (35–1) of 177 cm3 STP (CH4 )/cm3 , while the largest DC (65–5.8) reached was 183 cm3 STP (CH4 )/cm3 , for the JST-S structure The results are comparable with the previous studies and DOE 2000 target for methane storage (180 cm3 STP /cm3 ), as displayed in Table [43] This finding was attributed to the appropriate porous parameters for methane storage, as reported in Martin’s study [32] Notably, JST-S has a pore size of 10.7 Å, whereas NPT-S gave a pore diameter of 19.5 Å, as illustrated in Figure Figure (a) Isotherms of total volumetric CH4 uptake at 298 K from to 85 bar, and (b) CH4 delivery capacity of NPT-S and JST-S Table presents the delivery capacity of 11 ZCOF structures, which exhibited excellent performances for methane storage In total, NPS-S and JST-S give the best methane uptake, as shown in Figure 5a In particular, Figure 5b indicated that NPT-S gave the largest DC (35–1) of 177 cm3STP (CH4)/cm3, while the largest DC (65–5.8) reached was 183 cm3STP (CH4)/cm3, for the JST-S structure The results are comparable with the previous studies and DOE 2000 target for methane storage (180 cm3STP/cm3), as displayed in Table [43] This finding was attributed to the appropriate porous 3.3 Methane Delivery Capacity The methane delivery capacity of the ZCOF selected structures is calculated as follows [32]: DC (35–1) = the CH4 adsorption at 35 bar − the CH4 adsorption at bar Materials 2020, 13, 3322 DC (65–5.8) = the CH4 adsorption at 65 bar − the CH4 adsorption at 5.8 bar (1) of 11 (2) Figure (a) Isotherms of total volumetric CH4 uptake at 298 K from to 85 bar, and (b) CH4 delivery Figure of (a)NPT-S Isotherms total volumetric CH4 uptake at 298 K from to 85 bar, and (b) CH4 delivery capacity and of JST-S capacity of NPT-S and JST-S Table Comparison of the methane uptake of NPT-S and the other COFs at 35 bar and 298 K Table presentsSacc the delivery ZCOF structures, which exhibited excellent Dpore capacity Vporeof 11CH CH4 Delivery Uptake ZCOFs Ref /g) /cm3 ) 3) (m2 /g) storage (Å) In total, (cm (cm3 /cm performances for methane NPS-S and(cm JST-S give the best methane uptake, as shown COF-102-Ant 2720 Figure- 5b indicated 0.75 that NPT-S 215 gave the largest 180 DC (35–1) of[25] in Figure 5a In particular, 177 cm3STP COF-103-Eth-trans 4920 1.36 206 192 [25] 3 (CH4)/cm , while the largest DC (65–5.8) reached was 183 cm STP (CH4)/cm , for the JST-S structure COF-102-1,4-2I 181 [26] TheCOF-102-I results are comparable with the previous- studies and (180 176DOE 2000 target 169 for methane storage [31] 3 COF-102-Cl - [43] This [31] porous cm STP /cm ), as displayed in Table finding169 was attributed165 to the appropriate COF-1 750 COF-5 1670 27 COF-6 750 COF-8 1350 16 COF-10 1760 32 Materials 2020, 13, x COF-102 3620 12 COF-103 3530 12 parameters for methane NPT-S 2548 storage, 19.5as 0.30 1.07 0.32 0.69 1.44 1.55 1.54 reported 0.502in 55 73 101 85 53 113 105 Martin’s194 study Notably, 177 [32] JST-S 10.7 Å, whereas NPT-S gave a pore diameter of 19.5 Å, as illustrated in Figure [44] [44] [44] [44] [44] of 11 [44] [44] hasThis a pore worksize of Figure The spheres in in black, pink, andand orange denote C, H, Figure6.6 Two TwoZCOF ZCOFstructures: structures:NPT-S NPT-Sand andJST-S JST-S The spheres black, pink, orange denote C, and S atoms, respectively The yellow balls represent the pore size H, and S atoms, respectively The yellow balls represent the pore size 3.4 CH4 Adsorption Sites Table Comparison of the methane uptake of NPT-S and the other COFs at 35 bar and 298 K To date, only several studies provide the mechanism for CH4 adsorption in porous materials Dpore Vpore CH4 Uptake CH4 Delivery Ref Sacc For instance, Mendoza-Cortes et al indicated that the various 3D-COFs, including COF-105, COF-103, ZCOFs 3 3 COF-102-Ant COF-103-Eth-trans COF-102-1,4-2I COF-102-I COF-102-Cl (m /g) 2720 4920 - (Å) - (cm /g) 0.75 1.36 - (cm /cm ) 215 206 176 169 (cm /cm ) 180 192 181 169 165 [25] [25] [26] [31] [31] Materials 2020, 13, 3322 of 11 and COF-102, contains the adsorption centers on the surface of the benzene ring [5] In this work, we propose that the CH4 adsorption sites can be on the face of the thiophene, furane, and pyrrole rings, Materials 2020, 13, x of 11 as illustrated in Figure Figure Figure 7 The The adsorption adsorption of of CH CH44 on on the the surface surface of of thiophene thiophene (a), (a), furane furane (b), (b), and and pyrrole pyrrole rings rings (c) (c) for for YYY-S, YYY-O, and YYY-N, respectively YYY-S, YYY-O, and YYY-N, respectively 3.5 The Formation Energy of JST-S and NPT-S 3.5 The Formation Energy of JST-S and NPT-S The heat of formation is a powerful means to predict the thermodynamic stability of any structures The heat of formation is a powerful means to predict the thermodynamic stability of any The enthalpy of formation with a negative value indicates that the considered compound is stable in structures The enthalpy of formation with a negative value indicates that the considered compound terms of thermodynamic In this research, the reaction enthalpy for JST-S and NPT-S generation was is stable in terms of thermodynamic In this research, the reaction enthalpy for JST-S and NPT-S determined from the change in the total enthalpy between the products and reactants They were generation was determined from the change in the total enthalpy between the products and calculated from reaction (3) and (4): reactants They were calculated from reaction (3) and (4): 1818 Cgraphite + +4 4HH (JST-S) 2++1/2 Cgraphite 1/2SS88→ →CC18 18H H8SS44 (JST-S) (3) (3) Cgraphite + 3/2 S8 → C54H24S12 (NPT-S) 5454 Cgraphite + +1212HH + 3/2 S8 → C54 H24 S12 (NPT-S) (4) (4) The reactants reactants selected state in in nature, include graphite, hydrogen gas, gas, and The selected to tobe bethe thebest beststable stable state nature, include graphite, hydrogen sulfur (rhombic) Therefore, their standard enthalpy quantities and sulfur (rhombic) Therefore, their standard enthalpyofofformations formationsisiszero zero The The negative negative quantities exhibited in Table 4, implied that JST-S and NPT-S could be synthesized in the experiment exhibited in Table 4, implied that JST-S and NPT-S could be synthesized in the experiment Table4 Optimized Optimized crystal crystal structure structure lattice latticeparameters parameters Table ZCOF ZCOF JST-S NPT-SJST-S NPT-S Symmetry Atom/cell Symmetry Atom/Cell Pa-3 720 Pm-3 Pa-3 540 720 Pm-3 540 Lattice Parameter (Å) Lattice Parameter (Å) 27.3204 27.3204 25.0125 25.0125 ∆H (kJ/mol) ∆H (kJ/mol) −34823 × 103 −34,823 × 10×3 103 −8705 −8705 × 103 Conclusions Conclusions In summary, we have shown the design strategy of a new covalent organic framework by using In summary, haveinshown designthiophene, strategy offuran, a new and covalent organic framework bywe using carbon to replace we silicon zeolitethe through pyrrole linkers, named so can carbon to replace silicon in zeolite through thiophene, furan, and pyrrole linkers, named so we can obtain 300 ZCOF structures with 100 topologies of zeolite The typical porous parameters, including obtain 300 ZCOF structures topologies zeolite were The typical porous parameters, the accessible surface area, with pore100 size, and poreofvolume analyzed to evaluate the including quality of the accessible surface area, size, and pore volume analyzed evaluate the ZCOFs material through thepore Zeo++ software The resultswere reveal that thetosurface area ofquality ZCOFs of is ZCOFs material through the Zeo++ software The results reveal that the surface area of ZCOFs larger than that of zeolites, which is favorable for methane storage Notably, RWY-N displayed the is largeraccessible than that surface of zeolites, is favorable for methane storage Notably, RWY-N displayed largest areawhich of 3437 m2/g, proposed for the promising material in gas storage the largest accessible area ofmaterials, 3437 m2 /g,eleven proposed for the promising materialBOZ-S, in gas storage applications Amongsurface 300 ZCOFs optimal structures involving JSR-N, applications Among 300 ZCOFs materials, eleven optimal structures involving BOZ-S, JSR-N, JSR-O, JSR-O, JSR-S, JST-S, NPT-S, OBW-N, OBW-S, RWY-N, RWY-O, and RWY-S exhibited good methane JSR-S, JST-S, ability NPT-S, OBW-N, OBW-S, RWY-N, RWY-O,the andlargest RWY-SDC exhibited methane adsorption In particular, NPT-S displayed (35–1) good of 177 cm3STP adsorption (CH4)/cm3, 3 , whereas JST-S 3 ability In particular, NPT-S displayed the largest DC (35–1) of 177 cm (CH )/cm STP finding can be comparable whereas JST-S exhibited the best DC (65–5.8) of 183 cm STP (CH4)/cm This exhibited beststandard DC (65–5.8) 183 cm3the (CH4 )/cm3 of This findingof can be comparable the also old STP calculation to the oldthe DOE In of addition, enthalpy NPT-S and JST-Stowas DOE standard.byInthe addition, the calculation enthalpy of NPT-S JST-S was also by implemented DFT method, showingofnegative values Thisand result implied thatimplemented these structures could be prepared in the experimental study Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, Figure S1: Design strategy of ZCOFs with thiophene linker The spheres in black, pink, yellow denote C, H, and S atoms, respectively, Figure S2: Isotherms of total volumetric CH4 uptake at 298 K from to 85 bar of (a) RWY-X, and (b) Materials 2020, 13, 3322 of 11 the DFT method, showing negative values This result implied that these structures could be prepared in the experimental study Supplementary Materials: The following are available online at http://www.mdpi.com/1996-1944/13/15/3322/s1, Figure S1: Design strategy of ZCOFs with thiophene linker The spheres in black, pink, yellow denote C, H, and S atoms, respectively, Figure S2: Isotherms of total volumetric CH4 uptake at 298 K from to 85 bar of (a) RWY-X, and (b) JRN-X (X = N, O, S), Figure S3: (a) ctn and bor topologies, (b) the building blocks for designing new COFs, (c) the reactions from various reactants to created new COFs, Table S1: The parameter of 300 Z-COF structures, Computer Code: NPT-S, 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