Di-tert-butylphosphate Derived Thermolabile Calcium Organophosphates: Precursors for Ca(H2PO4)2, Ca(HPO4), α-/β-Ca(PO3)2, and Nanocrystalline Ca10(PO4)6(OH)2

Calcium Phosphate-Based Nanomaterials: Preparation, Multifunction, and Application for Bone Tissue Engineering

Calcium phosphate is the main inorganic component of bone. Calcium phosphate-based biomaterials have demonstrated great potential in bone tissue engineering due to their superior biocompatibility, pH-responsive degradability, excellent osteoinductivity, and similar components to bone. Calcium phosphate nanomaterials have gained more and more attention for their enhanced bioactivity and better integration with host tissues. Additionally, they can also be easily functionalized with metal ions, bioactive molecules/proteins, as well as therapeutic drugs; thus, calcium phosphate-based biomaterials have been widely used in many other fields, such as drug delivery, cancer therapy, and as nanoprobes in bioimaging. Thus, the preparation methods of calcium phosphate nanomaterials were systematically reviewed, and the multifunction strategies of calcium phosphate-based biomaterials have also been comprehensively summarized. Finally, the applications and perspectives of functionalized calcium phosphate biomaterials in bone tissue engineering, including bone defect repair, bone regeneration, and drug delivery, were illustrated and discussed by presenting typical examples.

Emerging Phosphate-Functionalized Co3O4/Kaolinite Composites for Enhanced Activation of Peroxymonosulfate

The Fenton-like reaction, as one of the most efficient strategies to generate radical species for the degradation of environmental pollutants, has attracted considerable attention. However, engineering low-cost catalysts with excellent activity by phosphate surface functionalization has seldom been used for the activation of peroxymonosulfate (PMS). Herein, emerging phosphate-functionalized Co₃O₄/kaolinite (P-Co₃O₄/Kaol) catalysts have been prepared by hydrothermal and phosphorization. Kaolinite nanoclay with rich hydroxyl groups plays a vital role in realizing phosphate functionalization. The results indicate that P-Co₃O₄/Kaol shows superior catalytic performance and excellent stability to the degradation of Orange II, which could be attributed to the existence of phosphate that promotes the adsorption of PMS and the electron transfer of Co²⁺/Co³⁺ cycles. Furthermore, the ^•OH radical was identified as the dominating reactive species for the degradation of Orange II compared to the SO₄^•- radical. This work could offer a novel preparation strategy for emerging functionalized nanoclay-based catalysts for effective pollutant degradation.

A rigid calcium 2-ethylhexylphosphate one-dimensional polymer: synthesis, structure, thermal behaviour and decomposition chemistry

The reactivity of two different phosphate esters has been explored with calcium ions. The reaction of calcium oxide with a mixture of mono/bis 2-ethylhexyl phosphate and 1,10-phenanthroline leads to the formation of the 1-D polymer [(phen)Ca(ehpH)₂]_n (1). On the other hand, the reaction of Ca(OAc)₂ with trimethyl phosphate in the presence of 1,10-phenanthroline however yields needle-shaped colourless crystals of [(phen)Ca(OAc)₂]_n (2). Compounds 1 and 2 have been characterized by various spectroscopic and analytical techniques. The solid-state structures have been determined by single crystal X-ray diffraction studies. The arrangement of rigid and flexible parts in 1 makes it an interesting compound to be studied for its thermal behaviour. DSC experiments performed above and below room temperature reveal thermal transitions in both the ranges, where below room temperature transition is prominent. A combination of variable temperature powder and single crystal X-ray diffraction experiments provides further insights into these transitions. Solid-state bulk thermolysis of 1 at 500 °C leads to an amorphous material contaminated with graphitic carbon which upon further heating to 600 °C produces crystalline α-Ca(PO₃)₂.

Dynamic Supramolecular Polymers Based on Zinc Bis(diorganophospate)s: Synthesis, Structure and Transformations in Solid State and Solutions

The synthesis, structure and some properties of coordination polymers composed of linear zinc bis(diorganophospate)s (ZnDOPs) with a general formula of Zn[O₂P(OR)₂]₂ (where R = CH₃, C₂H₅, n-C₄H₉, or 2-ethylhexyl group) are described. Hybrid (co)polymers obtained by different procedures were characterized by means of powder XRD, DSC, SEM, TGA coupled with mass spectrometry of the evolved gases and rheological measurements, as well as FTIR and NMR techniques. The morphology, thermal transformations and solubility of ZnDOPs strongly depend on the type of organic substituent in the O₂P(OR)₂ ligands and the thermal history of the sample. Because of this, one can obtain highly crystalline rods, semicrystalline powders, as well as rubbery materials exhibiting a second-order transition below −50 °C. Polymeric chains formed by ZnDOPs undergo a reversible dissociation in polar organic solvents (e.g., methanol, DMSO), which allows for easy modification of their composition and physicochemical properties via a simple exchange of diorganophosphate anions. Some of the ZnDOPs were investigated as the latent curing agents for epoxides. On the basis of rheological and DSC studies, it is evident that ZnDOPs catalyze very effectively the cross-linking process within the 130–160 °C temperature range.

Alkali Metal Di-tert-butyl Phosphates: Single-Source Precursors for Homo- and Heterometallic Inorganic Phosphate Materials

The reaction of alkali metal acetates, M(OAc)·nH₂O (M = Li, Na, K), with thermally and hydrolytically unstable di-tert-butylphosphate ((^tBuO)₂PO₂H, dtbp-H) in a 1:1 molar ratio in MeOH at room temperature leads to clean formation of group 1 metal phosphates [Li(μ-dtbp)]_n (1), [Na(μ-dtbp)]_n (2), and [K₄(μ-dtbp)₄(μ-H₂O)₃]_n (3). All three compounds are essentially M/L 1:1 complexes. Owing to the presence of larger potassium ions, additional coordinated water molecules are found in 3, which has been further employed as a precursor for the synthesis of a mixed-metal phosphate polymer [CaK(μ-H₂O)₃(μ-dtbp)₃]_n (4) by reacting 3 with Ca(OAc)₂. Compounds 1-4 have been characterized by various analytical and spectroscopic techniques. Molecular structures of 1-4 have been established in the solid state by single-crystal X-ray diffraction studies, which reveal them to be one-dimensional polymers, where the adjacent metal centers are connected through -O-P-O- bridges formed by the dtbp ligand. These complexes are rare examples of analytically pure alkali metal alkyl phosphates bearing no additional N-donor ligands (other than dtbp ligands, only water molecules are coordinated to the metal centers). Therefore, these compounds can be employed as single-source precursors (SSPs) for nano-sized ceramic phosphates. The thermogravimetric analysis of 1-4 reveals the loss of thermally labile tert-butyl substituents of the organophosphate ligands to form organic-free phosphate materials in the temperature range 300-500 °C. Solvothermal decomposition of 1-3 in boiling toluene leads to the formation of corresponding dihydrogen phosphates M(H₂PO₄) (M = Li, Na, and K). The thermal decomposition of heterometallic 4 in the temperature range 400-800 °C leads to the formation of phase-pure mixed-metal calcium potassium metaphosphate CaK(PO₃)₃.