Metal-organic frameworks (MOFs) are crystalline porous materials comprised of metal nodes or clusters, bridged together by organic linkers [1]. By carefully choosing the right metals, linkers and reaction conditions, MOFs can be fine-tuned, making them highly attractive for various applications, such as gas storage and separation [2], selective adsorption [3], heterogeneous catalysis [4], controlled drug release [5], or even biomimetic study of enzymes [6]. The present study focuses on preliminary results obtained by reacting 1,3,5-tris(4carboxyphenyl)mesitylene (H3L) with 4,4’-bipyridyl and cobalt nitrate in various conditions. It was found that slight variations in reaction conditions lead to different outcomes. Thus, by using a lower temperature, the predominant SBU appears to be a Co-Co paddlewheel cluster. Moreover, by using a smaller H3L:4,4’-bipyridyl ratio, a linear trinuclear Co cluster was also observed. On the other hand, when the temperature used was higher, no paddlewheel motif was found. Instead, a dinuclear Co cluster, comprising one tetrahedral and one octahedral metal ion, was observed at a H3L:4,4’-bipyridyl ratio of 1:1. In all cases, mixtures of two or more products were obtained. Further research, meant to identify sets of conditions which will lead to single products, is underway.