# Mg-MOF-74: open metal sites for CO₂ capture

> In Mg-MOF-74, chains of magnesium ions joined by 2,5-dioxidoterephthalate line one-dimensional hexagonal channels. Removing the solvent leaves a bare Mg²⁺ site every few ångströms along each channel, and these hold CO₂ strongly. In a packed bed fed with CO₂ and methane, methane passes straight through while CO₂ is held back; the bed reaches 8.9 wt% dynamic capacity and gives the CO₂ up again at 80 °C.

- Page: https://www.labcanvas.com/templates/metal-organic-frameworks/mg-mof-74-co2-capture
- Open in the LabCanvas editor (LabCanvas account): https://www.labcanvas.com/editor.html?template=mg-mof74-co2-capture
- Updated: 2026-10-14
- Category: Metal–organic frameworks
- Method: CO₂ capture, bottom-up
- Starting materials: Magnesium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid (H₄dobdc) in DMF/ethanol/water (15:1:1)
- Product: Mg₂(dobdc): hexagonal one-dimensional channels lined with Mg²⁺ sites
- Key result: 8.9 wt% dynamic CO₂ capacity; facile CO₂ release at 80 °C (Britt et al. 2009). Mg gives the highest CO₂ uptake of the Mg, Co, Ni and Zn versions (Caskey et al. 2008)
- Figure: 1920 × 1080 px, 79 editable layers (11 generated objects with settings)

## Steps

1. **Solvothermal**: Mg(NO₃)₂·6H₂O and H₄dobdc in DMF/EtOH/H₂O (15:1:1) at 125 °C (Caskey et al. 2008)
2. **Framework**: Helical Mg–O chains (rod-shaped building units) joined by dobdc⁴⁻ into a honeycomb of channels (Rosi et al. 2005)
3. **Activation**: Solvent removed from the magnesium sites by heating under vacuum: open Mg²⁺ along every channel
4. **Separation**: CO₂/CH₄ fed through a packed bed: CH₄ breaks through at once, CO₂ is held (Britt et al. 2009)
5. **Regeneration**: CO₂ released at 80 °C

## Strengths

- Dense, strong CO₂ binding sites
- Regenerated at low temperature
- Light, abundant metal

## Limitations

- Water competes for the open sites
- Powders must be shaped into pellets for beds

## Uses

- Natural gas and biogas upgrading
- CO₂ capture from flue gas

## References

1. Britt et al., “Highly efficient separation of carbon dioxide by a metal-organic framework replete with open metal sites”, PNAS 2009. https://doi.org/10.1073/pnas.0909718106 (primary)
2. Caskey et al., “Dramatic Tuning of Carbon Dioxide Uptake via Metal Substitution in a Coordination Polymer with Cylindrical Pores”, J. Am. Chem. Soc. 2008. https://doi.org/10.1021/ja8036096 (method origin)
3. Rosi et al., “Rod Packings and Metal−Organic Frameworks Constructed from Rod-Shaped Secondary Building Units”, J. Am. Chem. Soc. 2005. https://doi.org/10.1021/ja045123o (further reading)

Credit: Redrawn and simplified after Britt et al., PNAS 2009 (doi:10.1073/pnas.0909718106), Caskey et al., JACS 2008 (doi:10.1021/ja8036096) and Rosi et al., JACS 2005 (doi:10.1021/ja045123o). Breakthrough curves schematic.

## Questions

**What does the “Mg-MOF-74: open metal sites for CO₂ capture” template show?** In Mg-MOF-74, chains of magnesium ions joined by 2,5-dioxidoterephthalate line one-dimensional hexagonal channels. Removing the solvent leaves a bare Mg²⁺ site every few ångströms along each channel, and these hold CO₂ strongly. In a packed bed fed with CO₂ and methane, methane passes straight through while CO₂ is held back; the bed reaches 8.9 wt% dynamic capacity and gives the CO₂ up again at 80 °C.

**What are the steps shown in “Mg-MOF-74: open metal sites for CO₂ capture”?** 1. Solvothermal: Mg(NO₃)₂·6H₂O and H₄dobdc in DMF/EtOH/H₂O (15:1:1) at 125 °C (Caskey et al. 2008). 2. Framework: Helical Mg–O chains (rod-shaped building units) joined by dobdc⁴⁻ into a honeycomb of channels (Rosi et al. 2005). 3. Activation: Solvent removed from the magnesium sites by heating under vacuum: open Mg²⁺ along every channel. 4. Separation: CO₂/CH₄ fed through a packed bed: CH₄ breaks through at once, CO₂ is held (Britt et al. 2009). 5. Regeneration: CO₂ released at 80 °C.

**What are the starting materials and the product?** Starting materials: Magnesium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid (H₄dobdc) in DMF/ethanol/water (15:1:1). Product: Mg₂(dobdc): hexagonal one-dimensional channels lined with Mg²⁺ sites.

**Which papers is “Mg-MOF-74: open metal sites for CO₂ capture” based on?** Britt et al., “Highly efficient separation of carbon dioxide by a metal-organic framework replete with open metal sites”, PNAS 2009 (doi:10.1073/pnas.0909718106); Caskey et al., “Dramatic Tuning of Carbon Dioxide Uptake via Metal Substitution in a Coordination Polymer with Cylindrical Pores”, J. Am. Chem. Soc. 2008 (doi:10.1021/ja8036096); Rosi et al., “Rod Packings and Metal−Organic Frameworks Constructed from Rod-Shaped Secondary Building Units”, J. Am. Chem. Soc. 2005 (doi:10.1021/ja045123o).

**Can I edit the “Mg-MOF-74: open metal sites for CO₂ capture” template?** Yes. Open it in the LabCanvas editor: all 79 layers are editable, including 11 generated objects (structures, plots, equipment) with their own settings. Change the text, colours and layout, then export PNG, TIFF, SVG or PDF.

**Do I need an account to use this template?** Not to view it here. To open and edit it, sign in to LabCanvas or create a free account (the free plan keeps one design of each kind). Downloading the figure is part of LabCanvas Pro (US$19 a month or US$199 a year).