Goal: data-efficient search for the optimal COF, x * . In an exhaustive search, we would conduct expensive molecular simulations to predict the methane deliverable capacity of each candidate COF in the database-i.e., collect {(x, y = f (x)) : x ∈ X }-to find the COF x * ∈ X with the highest deliverable capacity. In contrast to an exhaustive search, instead, our goal is to find the optimal COF x * efficiently-while conducting expensive molecular simulations in only a small proportion of the candidate COFs.