Metal-organic frameworks (MOFs), synthesized using metal containing nodes and multidentate organic linkers, are one family of porous materials that have attracted significant interest for use in a range of sectors due to their inherent properties, including large surface areas and uniform porosities, which can be functionalized to suit specific applications. As a result, myriad MOFs have been synthesized [
1] and characterized with respect to applications in adsorption [
2,
3], catalysis [
4,
5], sensing [
6,
7,
8], gas storage [
2,
9,
10] and separation [
3,
11]. The field of carbon capture is a key potential area for development of nanoporous materials, including MOFs [
3], which present new structural effects, including the selective diffusion of guest species [
11,
12], that can be exploited to enhance adsorption and/or retention of gases. Increasing greenhouse gas emissions, of which carbon dioxide (CO
2) is a major constituent, have contributed to global climatic changes, hence, amelioration methods are essential [
13] to stem the rise and, possibly, reverse current upward trends. Anthropogenic energy consumption currently requires the use of fossil fuel powered electricity plants. Such point sources, with carbon capture capabilities, utilize the most technologically feasible methods of carbon capture at this time [
3], including absorption of CO
2 gas in aqueous alkanolamine solutions to afford separation [
14]; however, such methods suffer a number of problems, comprising significant energy penalties for alkanolamine recovery (related to the high heat capacity of water), solvent degradation and associated waste products, as well as contaminant issues. As an alternative, the use of solid MOF adsorption beds can offer reduced processing issues, such as increased thermal stability [
3], as well as a reduction in energy demand, as many MOFs exhibit lower heat capacities and offer physical or pseudo-physical sorption compared to the chemical reactions observed for amines. The application of MOFs in gas sensing and membrane-based separation processes is a growth area [
15,
16,
17,
18], benefitting from the mild synthesis conditions, modular constructive approaches, tunability of porosity and functionalization of MOFs, which have also shown high chemical and thermal stability [
19,
20,
21], and recent work has looked to apply MOFs to CO
2 adsorption to ameliorate the effects of energy related emissions [
22,
23]. These studies have focused on modifying either the secondary building units (SBUs) or multidentate organic ligands to enhance CO
2 adsorption; exploitation of unsaturated metal centers (UMCs) of SBUs [
24,
25] obtained via removal of terminal ligands invokes interactions between the UMCs and the highly polarizable quadrupole moment of CO
2. Alternatively, researchers have decorated the directing ligands using nitrogen containing groups, e.g., azo, triazole, tetrazole, acylamide, which are subsequently incorporated into the MOF structure; these nitrogen rich groups act as Lewis base sites, whereby their localized dipoles induce dispersive and electrostatic forces in the quadrupole moment of the Lewis acid CO
2, and the resulting MOFs exhibit enhanced CO
2 adsorption uptakes [
26,
27,
28,
29]. Consequently, we have synthesized and characterized a family of MOFs using the nitrogen containing ligand 1,4-bis(pyridin-4-yl)-1,2,4,5-tetrazine (pytz), with SBUs based on transition metal elements with the aim to reduce overall costs of manufacture and create a more sustainable MOF system. Herein, we report three new synthesized crystal structures [Zn(pytz(hydrolyzed))
2(OH
2)
2(OCOCH
3)
2]·H
2O, [Ni(pytz)
1.5(NO
3)
2]·
nDCM (
n = 2–3) and [Co
2(pytz)
3(NO
3)
4]·
nDCM (
n = 4–6). The CO
2 adsorption behavior of [Co
2(pytz)
3(NO
3)
4]·
nDCM (
n = 4–6) is also presented.