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Published online: 10 June 2009 | doi:10.1038/nchina.2009.124

Metal–organic frameworks: Helping the environment

Anne Pichon

Introduction

© (2009) ACS

Metal–organic frameworks (MOFs) — metal ions interconnected by organic ligands — are highly porous crystals suitable for applications such as gas storage, chemical separation and catalysis. Flexible ligands with imidazole (a five-member nitrogen-containing aromatic ring) donors and polycarboxylate ligands are common building blocks for the construction of MOFs. Lili Wen and Dongfeng Li at Central China Normal University in Wuhan and co-workers¹ have explored their crystal-making options and constructed six MOFs using both rigid imidazole-containing and carboxylate ligands.

The researchers obtained the MOF crystals by cooling a heated mixture of rigid imidazole-containing ligands, carboxylate ligands, metal ions (including copper, manganese, cobalt and cadmium), sodium hydroxide and water. They characterized the structures of the MOFs and found one of the samples to have a two-dimensional framework, one to have a triply interpenetrating three-dimensional framework, and four to have a trinodal three-dimensional framework (pictured).

The researchers also found that the frameworks of cobalt and cadmium ions hastened the degradation of organic dyes under ultraviolet or visible light. The cobalt-based framework had higher photocatalytic activity, probably because of the metal's electronic structure. The researchers suggest that the novel MOF may be promising for use as a catalyst in wastewater treatment.

The authors of this work are from:
Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, China; Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China; Key Laboratory of Catalysis and Materials Science, State Ethnic Affairs Commission and Ministry of Education, South-Central University for Nationalities, Wuhan, China.

Reference

1. Wen, L. L., et al. Structures, photoluminescence, and photocatalytic properties of six new metal-organic frameworks based on aromatic polycarboxylate acids and rigid imidazole-based synthons. Cryst. Growth Des. doi:10.1021/cg900317d (2009). | Article |