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Thiol-functionalization of metal-organic framework by a facile coordination-based postsynthetic strategy and enhanced removal of Hg²⁺ from water
Summary:
The authors from Anhui University (Laboratory of Advanced Porous Materials, School of Chemistry and Chemical Engineering) and University of Science and Technology of China (National Synchrotron Radiation Laboratory) developed thiol-functionalized [Cu₃(BTC)₂]ₙ (HKUST-1) with tunable S/Cu ratios, achieving high Hg²⁺ adsorption affinity (Kd=4.73×10⁵ mL/g) and capacity (714.29 mg/g) in water treatment.
Background:
1. To address heavy metal (e.g., Hg²⁺) pollution in water, previous researchers used adsorption (simple, low-cost) with adsorbents like thiol-functionalized mesoporous silica. These silica adsorbents have high efficiency but require complex synthesis (large surfactants, multiple extractions/calcination). MOFs show potential but lack targeted Hg²⁺ adsorption strategies.
2. The authors proposed a facile coordination-based postsynthetic modification (PSM): using HKUST-1’s coordinatively unsaturated metal centers (UMCs) to graft dithioglycol, preparing thiol-functionalized MOFs with tunable thiol content, which exhibit excellent Hg²⁺ removal performance.
Research Content:
1. Synthesis
-HKUST-1 synthesis: 4.5 mmol Cu(NO₃)₂·3H₂O (1.087 g) dissolved in 15 mL deionized water, mixed with 2.5 mmol H₃BTC (0.525 g) in 15 mL ethanol. Stirred 30 min, transferred to 50 mL Teflon autoclave, heated at 120°C for 12 h. Product filtered, washed, dried at 150°C (yield: 65.04% based on Cu).
-Thiol functionalization: 0.1 g dehydrated HKUST-1 (150°C, 12 h) suspended in 10 mL anhydrous toluene. Added 0.5/1/1.5 mL 0.24 mol/L dithioglycol-toluene solution (samples A/B/C), stirred 24 h at room temperature. Filtered, washed with ethanol, vacuum-dried (S/Cu ratios: 0.18, 0.92, 1.52).
2. Characterizations
1.BET & pore size: Pristine HKUST-1: S BET=1492.19 m²/g, Vt=0.75 cm³/g; samples A/B/C: S BET=800.42/331.39/79.92 m²/g, Vt=0.38/0.18/0.05 cm³/g (pore blocking by dithioglycol).
2.SEM: Pristine HKUST-1: 8 μm octahedra (smooth surface); samples A/B: rougher surfaces; sample C: irregular particles (excessive dithioglycol caused partial decomposition).
3.Other tests:
- PXRD: Samples A/B retain HKUST-1晶型; sample C shows reduced diffraction intensity (loss of crystallinity).
- IR: Functionalized samples have C-H (2900 cm⁻¹), S-H (2581 cm⁻¹), C-S (686 cm⁻¹) peaks (dithioglycol grafting).
- EDX: Samples A/B/C have S contents: 0.83/4.24/6.98 mmol/g.
3. Application
Tested for Hg²⁺ removal from water (10 mg adsorbent + 10 mL Hg²⁺ solution, 24 h shaking):
- Sample B: Removes 90.74%-99.79% Hg²⁺ (initial concentration: 0.081-715.52 mg/L); maximum adsorption capacity=714.29 mg/g (Langmuir model), Kd=4.73×10⁵ mL/g.
- Pristine HKUST-1: No detectable Hg²⁺ adsorption.
4. Mechanism
- Dithioglycol’s -SH coordinates with HKUST-1’s UMCs, grafting thiol groups into MOF pores (confirmed by IR and reduced BET/pore volume).
- Thiol groups (-SH) have strong affinity for Hg²⁺, enabling high adsorption. Adsorption follows Langmuir model (monolayer adsorption) and pseudo-second-order kinetics (k₂=0.13 g·mg⁻¹·min⁻¹, R²=0.9999), indicating chemical adsorption dominates.
Outlook:
This research develops a simple, low-cost route to thiol-functionalized MOFs for Hg²⁺ removal, solving the complexity of traditional adsorbents. It provides a template for MOF functionalization via coordination chemistry, promoting applications in dye adsorption, CO₂ capture, and sensing.
Thiol-functionalization of metal-organic framework by a facile coordination-based postsynthetic strategy and enhanced removal of Hg²⁺ from water
Authors: Fei Ke, Ling-Guang Qiu, Yu-Peng Yuan, Fu-Min Peng, Xia Jiang, An-Jian Xie, Yu-Hua Shen, Jun-Fa Zhu
DOI: 10.1016/j.jhazmat.2011.08.069
Link: https://www.sciencedirect.com/science/article/pii/S0304389411010879
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