Therefore, the first selection criterion is to select building blocks, especially linkers, that are known to absorb visible light. A logical choice is linkers composed of known chromophores with conjugated π-systems (e.g., porphyrin and pyrene). Selected linkers thus contain, for example, porphyrin (ol50, see Figure ), and thiazole (ol64, see Figure ). Both are expected to be active in the visible range due to highly conjugated π orbitals and high electronic density. Among others, we included pyrazolate-, triazolate-, and thiolate-based metal-linker bond chemistry to generate structures going beyond the conventionally used carboxylate-based chemistry in literature.