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15. Multifuntional Zeolitic Porous Chalcogenide

Author

Chen, Xitong

Subjects
Chemistry
Abstract

Crystalline porous metal chalcogenides have attracted extensive attentions due to its integration of highly porous structure and semiconducting property. Our research group has made great contributions to the development of chalcogenide molecular clusters with their three-dimensional (3D) structures. While most of the previous efforts are devoted to developing new crystal structures, research on the functionalization of this kind of materials are somewhat ignored. As built from well-defined nanoclusters, the metal chalcogenide materials can build a bridge between the molecular clusters and the resulting three-dimensional structures. By controlling the chemical composition on the nano-sized clusters or tuning the host-guest chemistry in the frameworks, custom-design functionalization can be realized. Among them, zeolitic porous chalcogenide, possessing the zeotype structures, stands out due to its high thermal and chemical stability, high porosity, flexible chemical composition and accessible cation-exchange property. In the first part of this work, trimetallic zeolitic porous chalcogenides with tunable chemical compositions were successfully developed. The valence and ionic diameter of the metal cations, were found as the key factors affecting the self-assembling process. Through tuning the chemical composition with different atomic ratio in the molecular clusters, tunable band gaps can be successfully realized. The studies here build a bridge between the molecular semiconducting clusters and the resulting frameworks, providing a systematic investigation on the structural retention and alternation of zeolitic porous chalcogenides. The as-synthesized frameworks exhibit the selective photocatalytic properties. By integration of high porosity, semiconductivity and cation-exchange property, a promising platform is well demonstrated for the development of selective photocatalytic materials.In the second part, functionalization of zeolitic porous chalcogenide through cation exchange are well demonstrated. Because of their unique integration of the chalcogen-soft surface, high porosity, all-inorganic crystalline framework, and the tunable charge-to-volume ratio of exchangeable cations, a special family of porous chalcogenides for CO2 adsorption in terms of extraordinarily high selectivity, large uptake capacity, and robust structure is developed. Moreover, zeolitic porous chalcogenide can serve as the dual hard template for fabricating the heteroatom doped carbon materials for electrocatalytic reactions with high efficiency.

Published
2017

32. A Strategy for Constructing Pore‐Space‐Partitioned MOFs with High Uptake Capacity for C2 Hydrocarbons and CO2.

Author

Wang, Yong, Jia, Xiaoxia, Yang, Huajun, Wang, Yanxiang, Chen, Xitong, Hong, Anh N., Li, Jinping, Bu, Xianhui, and Feng, Pingyun

Subjects
POROUS materials, ADSORPTION capacity, GAS absorption & adsorption, SORPTION, HYDROCARBONS
Abstract

Introduction of pore partition agents into hexagonal channels of MIL‐88 type (acs topology) endows materials with high tunability in gas sorption. Here, we report a strategy to partition acs framework into pacs (partitioned acs) crystalline porous materials (CPM). This strategy is based on insertion of in situ synthesized 4,4′‐dipyridylsulfide (dps) ligands. One third of open metal sites in the acs net are retained in pacs MOFs; two thirds are used for pore‐space partition. The Co2V‐pacs MOFs exhibit near or at record high uptake capacities for C2H2, C2H4, C2H6, and CO2 among MOFs. The storage capacity of C2H2 is 234 cm3 g−1 (298 K) and 330 cm3 g−1 (273 K) at 1 atm for CPM‐733‐dps (the Co2V‐BDC form, BDC=1,4‐benzenedicarboxylate). These high uptake capacities are accomplished with low heat of adsorption, a feature desirable for low‐energy‐cost adsorbent regeneration. CPM‐733‐dps is stable and shows no loss of C2H2 adsorption capacity following multiple adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

Published
2020
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33. A Strategy for Constructing Pore‐Space‐Partitioned MOFs with High Uptake Capacity for C2 Hydrocarbons and CO2.

Author

Wang, Yong, Jia, Xiaoxia, Yang, Huajun, Wang, Yanxiang, Chen, Xitong, Hong, Anh N., Li, Jinping, Bu, Xianhui, and Feng, Pingyun

Subjects
POROUS materials, ADSORPTION capacity, GAS absorption & adsorption, SORPTION, HYDROCARBONS
Abstract

Introduction of pore partition agents into hexagonal channels of MIL‐88 type (acs topology) endows materials with high tunability in gas sorption. Here, we report a strategy to partition acs framework into pacs (partitioned acs) crystalline porous materials (CPM). This strategy is based on insertion of in situ synthesized 4,4′‐dipyridylsulfide (dps) ligands. One third of open metal sites in the acs net are retained in pacs MOFs; two thirds are used for pore‐space partition. The Co2V‐pacs MOFs exhibit near or at record high uptake capacities for C2H2, C2H4, C2H6, and CO2 among MOFs. The storage capacity of C2H2 is 234 cm3 g−1 (298 K) and 330 cm3 g−1 (273 K) at 1 atm for CPM‐733‐dps (the Co2V‐BDC form, BDC=1,4‐benzenedicarboxylate). These high uptake capacities are accomplished with low heat of adsorption, a feature desirable for low‐energy‐cost adsorbent regeneration. CPM‐733‐dps is stable and shows no loss of C2H2 adsorption capacity following multiple adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

Published
2020
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34. S-Doped Ni(OH)2 nano-electrocatalyst confined in semiconductor zeolite with enhanced oxygen evolution activity.

Author

Hu, Dandan, Wang, Xiang, Chen, Xitong, Wang, Yanxiang, Hong, Anh N., Zhong, Jun, Bu, Xianhui, Feng, Pingyun, and Wu, Tao

Abstract

Low-cost Ni(OH)2-based nanomaterials with various structures and morphologies are promising catalysts for efficient oxygen evolution reactions (OERs). However, homogenous Ni(OH)2 nanomaterials with abundant active sites suffer from low conductivity and easy aggregation, resulting in low catalytic activity and stability. Here, we report a new synthetic method capable of generating abundant and confined S-doped β-Ni(OH)2 nanoparticles (NPs) (3–5 nm) within a 3D semiconductor substrate, metal-chalcogenide semiconductor zeolite (CSZ). This method operates via sequential fluoride-assisted cationic stripping and in situ Ni(OH)2 generation and is demonstrated here as an effective method to synthesize Ni2+-containing CSZ that are known to defy direct synthesis. The resulting composite (denoted Ni(OH)2 NPs@CSZ) exhibited excellent OER performance with a very low overpotential of only 212 mV at a current density of 10 mA cm−2 in O2-saturated 1 M KOH solution, and low Tafel slope of 64.2 mV dec−1, which is superior to that of benchmark IrO2. DFT calculations indicate that the interaction between the embedded Ni(OH)2 NPs and the dopant, S2−, from the host CSZ played a crucial role in improving OER performance. This work provides a new path for developing high-performance Ni(OH)2-based OER catalysts and may also serve as a general approach for loading large amounts of other catalytically active NPs into semiconducting open frameworks to further optimize electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Published
2020
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43. From MOF‐74‐Zn to Triazolate‐Directed Nonsymmetric Assembly of Chiral Zn6@Zn6 Clusters.

Author

Yang, Huajun, Le, James, Dinh, Andy, Zhao, Xiang, Chen, Xitong, Peng, Fang, Feng, Pingyun, and Bu, Xianhui

Subjects
CARBOXYLATES, MATERIALS
Abstract

The creation of new cluster building blocks, as well as new ligand coordination modes, are among the most effective ways to develop new framework materials. Yet, large and chiral clusters are both difficult to create and relatively few. Here, by studying the competing coordination of different azolates against carboxylate and combined carboxylate/phenolate, it is shown that the impact of azolates in the MOF‐74 synthesis system differs dramatically, leading to the synthesis of MOF‐74, UTSA‐74, and CPM‐72 for 2‐methylimidazole, 1,2,4‐triazole, and 1,2,3‐triazole, respectively. The new CPM‐72 contains a novel chiral Zn12 triazolate cluster, which features a trigonal‐prismatic Zn6 core inside an octahedral Zn6 shell. In contrast with MOF‐74 with fully deprotonated and symmetrically bonded 2,5‐dihydroxyterephthalic acid (H4DOBDC), H4DOBDC adopts an unusual nonsymmetric bonding mode in CPM‐72 (carboxylate only at one end and carboxylate/phenolate at the other), resulting in a highly porous and intrinsically chiral 3D framework. The nonsymmetric bonding mode by H4DOBDC, apparently dictated by the chiral Zn12 cluster, can be replicated with 2‐hydroxyterephthalic acid (H3OBDC), leading to the synthesis of porous isoreticular CPM‐73. [ABSTRACT FROM AUTHOR]

Published
2019
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