Though taking place in a computer simulation and pertaining to the specific task of discovering COFs for Xe/Kr separations, our study hints at the potential for multi-fidelity Bayesian optimization to reduce the time and cost to discover new materials in a variety of contexts. While the cost in our work was computational runtime, costs will be much more significant in the bona fide laboratory, involving lab space, equipment/instrumentation, reagents, salaries of operators, etc.