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US-20260125559-A1 - SINGLE-CRYSTAL METAL-FREE HELICAL COVALENT POLYMERS

US20260125559A1US 20260125559 A1US20260125559 A1US 20260125559A1US-20260125559-A1

Abstract

This invention relates to the development of covalent organic frameworks (COFs) and/or covalent organic polymers (COPs) utilizing tellurium-based dynamic covalent bonds (—Te—O—B— and —Te—O—P—) to create high-quality single crystals with unique properties. This invention also provides concise and efficient methods to grow large single crystals of tellurium-based polymers, overcoming challenges associated with misassembly and poor crystallinity during synthesis. The tellurium-based COFs and COPs exhibit enhanced thermal and solvent stability, making them suitable for applications in catalysis, separation, and energy storage.

Inventors

  • Qichun Zhang
  • MIAOMIAO XUE

Assignees

  • CITY UNIVERSITY OF HONG KONG

Dates

Publication Date
20260507
Application Date
20241107

Claims (19)

  1. 1 . A metal-free helical covalent organic polymer, comprising a helical backbone formed from one or more tellurium atoms covalently bonded to organic phosphonic acid groups, the one or more tellurium atoms form a repeating unit that contributes to a helical structure, wherein the metal-free helical covalent organic polymer exhibits a metal-free composition and a three-dimensional or two-dimensional network arrangement, and wherein the metal-free helical covalent organic polymer exhibits a thermal stability at a temperature of at least 300° C.
  2. 2 . The metal-free helical covalent organic polymer of claim 1 , wherein the organic phosphonic acid groups are selected from the group consisting of 1,4-phenylenebis(phosphonic acid), naphthalene-2,6-diylbis(phosphonic acid), and benzene-1,3,5-triyltris(phosphonic acid).
  3. 3 . The metal-free helical covalent organic polymer of claim 1 , wherein the metal-free helical covalent organic polymer has a helical pitch of less than 10 nm.
  4. 4 . The metal-free helical covalent organic polymer of claim 1 , wherein the metal-free helical covalent organic polymer displays photocatalytic activity in oxidation of primary amines to imines under UV-visible light irradiation.
  5. 5 . The metal-free helical covalent organic polymer of claim 1 , wherein the metal-free helical covalent organic polymer forms single crystals with sizes greater than 200 μm.
  6. 6 . The metal-free helical covalent organic polymer of claim 1 , wherein the repeating unit is represented by a structural formula comprising —Te—O—P(═O)— or —Te—O—P— bonds.
  7. 7 . The metal-free helical covalent organic polymer of claim 6 , wherein the —Te—O—P— bonds are formed by incorporating the one or more tellurium atoms and [P═O] groups into the backbone.
  8. 8 . The metal-free helical covalent organic polymer of claim 1 , wherein covalent linkages between the one or more tellurium atoms and the organic phosphonic acid groups result in enhanced structural stability.
  9. 9 . The metal-free helical covalent organic polymer of claim 1 , wherein the one or more tellurium atoms improve charge separation during photocatalytic processes, leading to an enhancement in overall photocatalytic performance by at least 25% to 40% compared to conventional polymers.
  10. 10 . A metal-free helical covalent inorganic polymer represented by the formula {[Te(C 6 H 5 ) 2 ][PO 3 (OH)]} n , comprising a helical structure formed from angular anions incorporated into tellurium-oxygen chains, and phenyl units as side groups, wherein n indicates it is a polymer structure, and wherein the metal-free helical covalent inorganic polymer exhibits thermal stability up to 356° C. with minimal weight loss.
  11. 11 . The metal-free helical covalent inorganic polymer of claim 10 , wherein the helical structure exhibits a pitch of approximately 17.03 Å.
  12. 12 . The metal-free helical covalent inorganic polymer of claim 10 , wherein the angular anions are phosphates (PO 4 3− ) and/or their derivatives.
  13. 13 . The metal-free helical covalent inorganic polymer of claim 10 , wherein neighboring helical chains are interconnected by hydrogen bonding interactions, forming a pseudo-two-dimensional supramolecular layer structure.
  14. 14 . The metal-free helical covalent inorganic polymer of claim 13 , wherein adjacent helical layers exhibit opposite chirality, resulting in a racemic mixture.
  15. 15 . A metal-free covalent organic-inorganic hybrid framework, comprising a chiral cubic crystalline structure formed from non-carbon backbones, wherein the chiral cubic crystalline structure comprises a —Te—O—B—O— backbone composed of: tellurium (Te) atoms forming a backbone, wherein the Te atoms are linked by one or more covalent bonds, boron (B) atoms incorporated as nodes within the metal-free covalent organic-inorganic hybrid framework in a form of borate groups, and oxygen (O) atoms facilitating the formation of Te—O and B—O bonds, wherein the metal-free covalent organic-inorganic hybrid framework exhibits UV absorption in a range of 200-300 nm, and wherein the metal-free covalent organic-inorganic hybrid framework exhibits a thermal stability with a decomposition temperature of at least 310° C. considering a 5% weight loss.
  16. 16 . The metal-free covalent organic-inorganic hybrid framework of claim 15 , wherein the Te atoms are present in a form of tellurinyldibenzene (Te(Ph) 2 ) units.
  17. 17 . The metal-free covalent organic-inorganic hybrid framework of claim 15 , wherein the metal-free covalent organic-inorganic hybrid framework exhibits stability when exposed to various solvents and heat.
  18. 18 . The metal-free covalent organic-inorganic hybrid framework of claim 15 , wherein the framework consists of single crystals with dimensions of up to 400 μm.
  19. 19 . The metal-free covalent organic-inorganic hybrid framework of claim 15 , wherein the metal-free covalent organic-inorganic hybrid framework demonstrates a second harmonic generation (SHG) response comparable to that of potassium dihydrogen phosphate (KDP).

Description

FIELD OF THE INVENTION The present invention generally relates to the field of covalent organic materials and their applications in optics, photocatalysis, nonlinear optical (NLO) and room-temperature phosphorescence (RTP). It focuses on the development of tellurium-containing polymer crystals, particularly in one-, two-, and three-dimensional forms, to address challenges associated with their synthesis and stability. BACKGROUND OF THE INVENTION Covalent organic frameworks (COFs) are highly versatile materials that have garnered significant interest across various scientific fields. The development of COFs has shown significant potential in fields like catalysis, separation, energy storage, optoelectronics, and biosystems. Traditionally, most COFs have been built using dynamic covalent bonds, such as —C═N—, —B—O—, and —P—O—B—, which allow self-correction during assembly and enable the formation of large single crystals suitable for structural analysis. However, the library of available dynamic covalent bonds remains limited, resulting in challenges in diversifying the structural properties and functionalities of COFs. Additionally, many COFs suffer from poor crystallinity, which limits their use in applications requiring precise structural information, such as advanced catalysis and energy storage. Recent research has begun to explore the integration of heavy elements, such as tellurium, into COFs to form new types of dynamic covalent bonds. These bonds offer potential advantages, including self-correction during the COF assembly process and enhanced functionality. However, despite these advances, challenges such as improving thermal and solvent stability, as well as achieving specific properties like ultraviolet nonlinear optical (UV-NLO) behavior and photocatalytic efficiency, persist. Moreover, dynamic covalent bonds involving heavy atoms are still not widely utilized, and their impact on important properties like spin-orbit coupling (SOC) and intersystem crossing (ISC) for applications such as RTP remains underexplored. The preparation of covalent organic polymers (COPs) has also faced limitations, particularly with respect to growing high-quality single crystals that can be used for structural analysis. The ability to produce single crystals from COPs has been restricted by factors such as the poor reversibility of covalent bonds and the inherent challenges associated with stabilizing these materials in the presence of oxygen or under thermal conditions. Moreover, metal-free organic molecules are rarely able to exhibit room-temperature phosphorescence due to the quenching of triplet excitons by oxygen, presenting an additional obstacle in developing new functional materials. Therefore, there is a continuing need to develop advanced covalent polymers that can overcome these limitations. Improvements in the synthesis and stability of these materials will significantly benefit both academia and industry by enabling more robust applications in fields such as energy storage, catalysis, and optoelectronics. SUMMARY OF THE INVENTION To address the above-mentioned shortcomings, a first aspect of the present invention provides a metal-free helical covalent organic polymer, which includes a helical backbone formed from one or more tellurium atoms covalently bonded to organic phosphonic acid groups, the one or more tellurium atoms form a repeating unit that contributes to a helical structure. The metal-free helical covalent organic polymer exhibits a metal-free composition and a three-dimensional or two-dimensional network arrangement. The metal-free helical covalent organic polymer exhibits a thermal stability at a temperature of at least 300° C. In accordance with one embodiment, the organic phosphonic acid groups are selected from the group consisting of 1,4-phenylenebis (phosphonic acid), naphthalene-2,6-diylbis (phosphonic acid), and benzene-1,3,5-triyltris (phosphonic acid). In accordance with one embodiment, the metal-free helical covalent organic polymer has a helical pitch of less than 10 nm. In accordance with one embodiment, the metal-free helical covalent organic polymer displays photocatalytic activity in oxidation of primary amines to imines under UV-visible light irradiation. In accordance with one embodiment, the metal-free helical covalent organic polymer forms single crystals with sizes greater than 200 μm. In accordance with one embodiment, the repeating unit is represented by a structural formula comprising —Te—O—P(═O)— or —Te—O—P— bonds. In accordance with one embodiment, the —Te—O—P— bonds are formed by incorporating the one or more tellurium atoms and [P═O] groups into the backbone. The incorporation of the one or more tellurium atoms enhances the spin-orbit coupling (SOC) effects, contributing to unique electronic properties. In accordance with one embodiment, covalent linkages between the one or more tellurium atoms and the organic phosphonic acid groups result in enhanced structural stab