Designing of three mixed ligand MOFs in searching of length induced flexibility in ligand for the creation of interpenetration

Abstract

Interpenetrated metal organic frameworks (IMOFs) have occupied a top priority of interest in the last few decades due to their unexpected better potential applications in the various growing field. Interpenetrated framework is generally formed by coordination of metals with rigid ligands but flexible ligand shows more interesting results in some cases. It is well established that the length of used ligands, irrespective of flexibility and rigidity plays a vital role in making of these type of structures. In searching of IMOFs, we have synthesized three MOFs, {Cd(bix)0.5(adp)0.5(H2O)}n (1), {[Cd(bix)(2,2ꞌ–dmglu)].(H2O)}n (2) and {Cd(bpmp)(2,2ꞌ–dmglu)(H2O)].(H2O)}n (3) by using two different N,N-donor linkers bix {bix = 1,4-bis(imidazol-1-ylmethyl)- benzene}, bpmp { bpmp = 1,​4-​bis(4-​pyridinylmethyl)​piperazine} and two different substituted dicarboxylate adp {adp = adipate}, 2,2ꞌ–dmglu {2,2ꞌ–dmglu = 2,2ꞌ–dimethylglutarate}. Among the three complexes, three fold interpenetrated framework has been shown by complex 3 where long length more flexible N,N-donor ligand, bpmp { bpmp = 1,​4-​bis(4-​pyridinylmethyl)​piperazine}has been used. Gas sorption studies (H2, N2, and CO2) are performed with the three synthesized MOFs which substantially correlate with their framework. In case of complex 3, better hydrogen adsorption occurs compared to the other two complexes due to the greater lengths of NN donor connectivity and flexibility of bpmp ligand while all the three complexes show similar carbon dioxide and nitrogen adsorption.