Membranes, methods of making membranes, and methods of separating gases using membranes are provided. The membranes can include at least one hydrophilic polymer, at least one cross-linking agent, at least one base, and at least one amino compound. The methods of separating gases using membranes can include contacting a gas stream containing at least one of CO2, H2S, and HCl with one side of a nonporous and at least one of CO2, H2S, and HCl selectively permeable membrane such that at least one of CO2, H2S, and HCl is selectively transported through the membrane.