MOF

DETAILED HANDOUT: NH₂-MIL-53(Al) Synthesis (Hydrothermal) + Solar Photocatalysis

MOF for Renewable Energy (Solar Photocatalysis) • Prepared using Al(NO₃)₃·9H₂O + 2-Aminoterephthalic Acid (NH₂-BDC)

---

1. Aim

To synthesize NH₂-MIL-53(Al) (amino-functionalized aluminium MOF) by hydrothermal method and evaluate its solar photocatalytic performance under a solar simulator (renewable energy input).

2. Chemicals (Available / Required)

Chemical	Formula	Grade	Use
Aluminium nitrate nonahydrate	Al(NO3)3·9H2O	AR (≥98%)	Al source
2-Aminoterephthalic acid (NH2-BDC)	C8H7NO4	AR (≥99%)	Organic linker (light active)
Distilled / deionised water	H2O	—	Solvent
Methanol (for washing)	CH3OH	AR / HPLC	Washing to remove unreacted linker/salts

3. Equipment Needed

• Rotek fully automatic autoclave (Teflon-lined) — 100 mL or 50 mL
• Magnetic stirrer + hot plate
• Analytical balance (0.1 mg if possible)
• Measuring cylinder / volumetric flasks
• Filtration setup (Whatman filter paper) or centrifuge
• Drying oven (60–100 °C)
• Solar simulator (Class A) + UV–Vis spectrophotometer (for photocatalysis kinetics)

4. Safety

• Autoclave safety: Do not fill above 80% of Teflon liner volume. Ensure gasket is clean and seated.
• Al nitrate: oxidizing salt; avoid contact with organics; wash spills with water.
• Methanol: toxic and flammable; use in fume hood; keep away from flame.
• Wear gloves + goggles throughout.

5. Batch Size & Exact Quantities

This protocol is designed for a one-batch synthesis using a 1:1 molar ratio of Al-source and NH₂-BDC. Target: ~0.0025 mol scale (good for lab reproducibility).

Component	Moles	Molar mass (g/mol)	Exact mass	Notes
Al(NO3)3·9H2O	0.0025 mol	375.13	0.938 g	Al precursor
2-Aminoterephthalic acid (NH2-BDC)	0.0025 mol	181.15	0.453 g	Linker
DI water	—	—	35–40 mL	Solvent (adjust per liner volume)

Scaling rule: Multiply all masses by the same factor. Example: For 0.005 mol (double batch), use 1.876 g Al nitrate and 0.906 g NH₂-BDC.

6. Step-by-Step Synthesis Procedure (Strict)

6.1 Solution preparation (Room temperature)

1. Label two clean beakers: Beaker A (Al) and Beaker B (Linker).
2. Beaker A: Add ~20 mL DI water. Weigh 0.938 g Al(NO₃)₃·9H₂O and dissolve completely (stir 5–10 min).
3. Beaker B: Add ~15–20 mL DI water. Weigh 0.453 g NH₂-BDC and add slowly while stirring.
4. Continue stirring Beaker B for 20–30 min. (NH₂-BDC dissolves slowly; mild warming to 50–60 °C is allowed.)
5. Pour Beaker A into Beaker B slowly under stirring.
6. Stir the combined mixture for 30 min until a uniform suspension/solution is obtained.

It is normal if the mixture is slightly turbid. Do not add strong base/acids unless instructed.

6.2 Autoclave loading

1. Inspect Teflon liner for cleanliness; rinse with DI water and dry.
2. Transfer the reaction mixture into Teflon liner. Ensure fill volume is ≤ 80%.
3. Wipe the liner rim and gasket area clean (no particles).
4. Close autoclave tightly as per manufacturer instructions.

6.3 Hydrothermal reaction

1. Place autoclave in oven/autoclave heater.
2. Set temperature to 150 °C and hold for 12 hours.
3. After completion, allow to cool naturally to room temperature (do not force-cool).

6.4 Product recovery

1. Open autoclave carefully. Collect the solid product by filtration (or centrifugation).
2. Wash the solid with DI water 3× (each wash ~20–30 mL) to remove nitrates.
3. Wash with methanol 2× (~20 mL each) to remove residual linker/organics.
4. Dry the product at 80 °C overnight in a drying oven.

6.5 Activation (Recommended for better porosity)

1. Place dried MOF in a glass petri dish.
2. Heat at 120 °C for 4 hours (air oven).
3. Cool in a desiccator and store in an airtight vial labeled with batch date.

If vacuum oven is available, activation at 120 °C under vacuum is ideal.

7. Expected Observations

• Product typically appears as yellowish to pale brown powder (shade varies by conditions).
• Yield: typically few hundred mg to ~1 g depending on washing losses.

8. Characterization Checklist (What to run)

• XRD (CLIF): confirm NH₂-MIL-53(Al) crystalline pattern.
• BET (CLIF): surface area and pore-size distribution (after activation).
• SEM (CLIF): particle morphology/size.
• FTIR/Raman: confirm linker coordination (carboxylate modes), aromatic features.
• XPS: Al 2p and O 1s, N 1s features; surface chemistry.
• UV–Vis (diffuse reflectance if available): estimate optical bandgap (MOF is light active).

9. Solar Photocatalysis Test (Renewable Energy Demonstration)

Option A (Easiest): Dye degradation under solar simulator (model water purification)

Model pollutant: Methylene blue (MB)

9.1 Prepare MB solution (10 ppm)

• Dissolve 1.0 mg MB in 100 mL DI water (or 10 mg in 1 L).
• Record initial UV–Vis spectrum; note λ_max ~ 664 nm.

9.2 Photocatalysis setup

1. Add 50 mg NH₂-MIL-53(Al) to 100 mL of 10 ppm MB solution (catalyst dose = 0.5 g/L).
2. Stir in dark for 30 min (adsorption equilibrium).
3. Take 3 mL aliquot, filter quickly, measure absorbance at 664 nm → this is A₀.
4. Switch ON solar simulator and start timing.
5. Withdraw aliquots at 5, 10, 15, 20, 30, 45, 60 min. Filter, measure A_t.

9.3 Data processing

• Compute concentration ratio: C/C₀ = A_t/A₀
• Pseudo-first-order kinetics: ln(C₀/C) = kt
• Plot: (i) C/C₀ vs time, (ii) ln(C₀/C) vs time → slope = k

9.4 Mandatory controls (for publication-quality results)

• MB + light (no catalyst)
• MB + catalyst (dark)
• MB + catalyst + light (main experiment)

Reusability: recover MOF, wash with water+methanol, dry at 80 °C, reuse for 3 cycles.

10. Troubleshooting (Common Problems)

• Low yield: ensure correct temperature/time; avoid losing powder during washing; use gentle filtration.
• Poor crystallinity in XRD: increase reaction time to 18 h or reduce water volume slightly; ensure proper washing.
• Low photocatalytic activity: ensure adsorption equilibrium step; confirm solar intensity and stirring; use freshly activated MOF.
• Powder floating/clumping: reduce particle aggregation by mild sonication before experiment.

Record in lab notebook (mandatory): batch masses, total solvent volume, autoclave filling %, temperature/time, washing volumes, drying/activation conditions, yield, and all photocatalysis settings (light intensity, distance, stirring speed).